Troubleshooting is simply finding and fixing a problem. With the Chrysler TorqueFlite, identifying the problem and knowing where to look for its solution is sometimes tough. This article helps focus attention on the internal assemblies and exterior parts that often create common issues.
Like any device designed and assembled by humans, TorqueFlites are not infallible. Over time and with use, their elastomeric materials change due to fluid exposure and heat. Friction materials wear out. Springs change tension. Wear particles from gears and friction materials end up in the wrong places. Driver abuse and neglect take a toll. Eventually, several things combine to cause operational and shifting issues, noises, leaks, and worst case, catastrophic failures.
Troubleshooting is a bit more difficult now compared to when the TorqueFlites were new because, over time, owners have made “improvements,” swapped parts, enlarged transfer plate holes, and changed springs in the valve body. Many TorqueFlites degrade due to storage. Fixing them when they were newer was relatively straightforward; you made sure their parts met the original specifications and you adjusted everything according to factory specifications and engineering changes. Unfortunately, as time passes, original parts are replaced, and original engines and carburetors and the matching throttle pressure linkage, manifolds, and levers are long separated.
Combine several changes and it becomes apparent why it is much more difficult to predict and explain what could be wrong and why it may be tough to find and fix every problem. Unfortunately, (or fortunately, if you have fun doing it) TorqueFlites may simply need to be removed for repair. It is not uncommon to buy a vehicle that has what seems like a simple transmission issue, but that turns into something much more difficult. Often, you just have to return it to its original condition. Knowing the history of the transmission is very important, but many times, it may not be possible to get all the information needed.
In this chapter, information from factory and aftermarket literature is combined with input from experienced mechanics to highlight TorqueFlite operational issues, what could cause them, and what steps can be taken to correct them. Fortunately, because A-904s and A-727s are closely related, troubleshooting is similar.
There are three “Trouble” charts provided in Appendix B: one that deals with troubles that can be diagnosed and fixed with the transmission in the vehicle, a second that requires removal of the transmission/converter for repair, and a third that is exclusively for lock-up converter-equipped problems. Noises and fluid leaks are discussed.
This Tech Tip is From the Full Book, CHRYSLER TORQUEFLITE A-904 & A-727 TRANSMISSIONS: HOW TO REBUILD. For a comprehensive guide on this entire subject you can visit this link:
SHARE THIS ARTICLE: Please feel free to share this post on Facebook Groups or Forums/Blogs you read. You can use the social sharing buttons to the left, or copy and paste the website link: https://mopardiy.com/how-to-troubleshoot-a-chrysler-torqueflite-transmission/
There is a logical and ordered sequence that should be followed when troubleshooting a transmission. By doing it in this way, simple things can be identified and corrected first. One manufacturer states it most eloquently: “The logical and proper procedure is diagnosis before disassembly.” In other words, identify the problems and use your knowledge of how the TorqueFlite works before automatically jumping in and tearing it down.
Fortunately, there are a few basic things that cause most of the trouble.
- The fluid level is too high or too low.
- The throttle pressure is wrong.
- The engine is not running right.
- The shift linkage is not correct.
- The band(s) is out of adjustment.
And if correcting these easy things doesn’t fix the problem, there are always more complex things to look at.
- Hydraulic pressures are out of specification.
- Internal hydraulic issues are present.
- Mechanical failures have occurred.
- Mismatched parts and technology are combined.
Chapter 2 offered insight as to how the TorqueFlite actually works so one can understand what the transmission is doing in each gear. Diagnosing in the proper sequence helps the problem be identified quicker.
- The basic things should always be checked and corrected early.
- To gather additional operational data, a diagnostic road test can be taken (if drivable).
- After road testing is complete, you may be able to decide what is wrong. If not, hydraulic pressure tests can be made to provide more internal information.
- If after pressure testing, the problem is still not apparent, removal of the valve body lets an air-pressure test be made of the transmission to determine the condition of the hydraulic sections.
- Torque converter issues may be part of or even the whole problem; the “nerve-racking” converter stall test can be performed.
One of the things done to increase torque capacity is to increase the quantity of friction discs and steel plates in the front clutch retainer. This requires a larger, deeper retainer, thinner steels, thinner frictions, or a modified piston (along with extra return springs) or any combination thereof. For an A-727 behind a worked-over 340, I thinned some front steel plates by getting them ground and then smoothed them out with a light sand blast, followed by a lot of sanding. I then added thinner rear clutch friction discs and was able to install seven (I believe). It worked pretty well with a nice firm shift at wide-open throttle. After a few days, I needed to make a minor kickdown band adjustment to eliminate the spin-up that started during light throttle 2–3 shifts. I knew everything was right so it must have been just the kickdown band wearing in. A few more days and another band adjustment was needed. A few more days and another minor readjustment did not take care of it.
I knew the pressure was right and the fluid level was correct. The fluid looked a little darker, but that was expected. The throttle pressure was reset, but it was close enough. No way could it be my modifications. I suspected the kickdown band was failing so out the transmission came. The pump and the front clutch retainer, along with the kickdown band and kickdown servo, were removed. The band and servo were perfect. The front friction discs, unfortunately, were devoid of almost all friction material. Those custom steel plates that I just knew would smooth out and be polished by the “sort of rough” friction discs looked the same as when they were installed.
Would any additional tests have identified this issue? In this case, the history of the transmission needed to be understood. Testing the transmission may have provided some answers, but questioning the transmission mechanic’s background in physics would have told the story. (Always remember, steel plates have to be smooth and almost polished to avoid damage to the less durable paper-based material they interleave with. Rough metal almost always wins against paper.)
By combining (1) the information gathered from the tests, (2) data in the three troubleshooting charts, and (3) any known history of the TorqueFlite in question, you should be able to determine the problem and identify the fix needed.
Fortunately, some of the simplest things to check cause the highest percentage of problems. Pulling the dipstick to check the fluid level, verifying that the shift linkage is close, and checking the throttle pressure linkage can all be performed rapidly and without any tools.
Start by checking the fluid level. With the engine at a general idle speed and the fluid warm to hot, the fluid level in Neutral should be between the “full” and “add one pint” level. If it is too low, the pump, via the filter, can suck in air causing all types of hydraulic issues. It the level is too high, the gears and spinning parts can whip the fluid into a foam or froth, which also causes similar issues.
While checking the level, look at the fluid to be sure it is red or light brown; it should never be black, burnt smelling, or have flakes or tiny metal particulates in it. Newer fluids tend to smell more burnt so you may have to put a few drops on a white cloth to see if it is blackish or dark brown. If there is metal in the fluid or pieces of things floating around in it, it is likely too late.
With the fluid level verified, check the shift linkage, whatever kind yours has. Assuming the neutral starting switch is functional, move the shifter to “Park” or “P,” and if the starter spins over when you turn the key, it is good (so far). Move the selector to “N” and hit the key again. If it spins over in “N,” the linkage is probably pretty close. If it just misses each position by a little bit, look at the linkage to see if the pins are worn out, or the holes are elongated, or the plastic bushings are shot.
If you have an aftermarket shifter, you may have to slowly “feel it” through all the detent positions to be sure it is even close. At one extreme it has to be in “L” or “1” and at the other it has to be in “P.” Often, the levers that may have been put on your transmission may be the wrong length and you may have “P” or “L” (“1”) but not both.
As difficult as it is to drill holes or modify expensive aftermarket parts, levers may need drilling so “P” and “L” are correctly located and that in “N” and “P,” the starter spins over. Many times it is as simple as changing to the correct lever on the transmission manual valve shaft but it may be hard finding the right one. The total distance the shifter lever moves at the cable attaching point has to match the distance the cable attaching point of the manual lever moves.
Throttle Pressure Linkage
This is by far the most important signal the stock TorqueFlite needs to work properly. The throttle pressure signal tells the valve body where the carburetor or throttle body lever is at any given point in time. Is the engine idling or under load? Is the throttle wide open or did the driver just lift off the gas? The linkage transmits the signal that tells the transmission how hard to shift, when to shift, when to downshift, and when to ease up or increase pressures. If the throttle pressure linkage is wrong, most everything about the shift is wrong. It must be correct.
Unfortunately, even though the “top side” of the engine’s linkage can be correct, the lever on the transmission may be wrong. The 2- and 4-barrel engines often had different linkage lengths and shapes, so it may be as easy as switching to a shorter lever or one with the different angle if your linkage is still off. As long as the throttle pressure linkage follows the carburetor or throttle body pin and ends up close to full detent when the carburetor or throttle body is wide open and it goes back when at idle, you can get by without damage. Leaving it off because you do not need “kickdown” is never, ever acceptable unless the lever on the transmission is tied to keep pressure on the internal throttle valve. Even then it is truly only correct at one position unless it is a manual valve body and the pressure is maxed out.
There is another way to take care of mismatched throttle pressure linkage. Bouchillon Performance Engineering and Lokar Performance Products sell cable-operated throttle pressure kits that replace the OEM mechanical rods and linkage. The parts they come with help you adapt to most any combination, and their instructions detail how to set the pressure correctly at idle and wide-open-throttle conditions. If you have changes that render the rod-type linkage too difficult to use, either of these should help.
“Adapting” to Change
If you have a non-stock carburetor or throttle body, adapters from Edelbrock and Holley help get the linkage adjustments back within stock specifications. The key thing is the throttle valve inside the valve body needs to move in unison with the throttle pin on the carburetor or throttle body. For this to happen, the linkage from the manual shaft on the valve body to the throttle body or carburetor needs to be right and have similar geometry. In other words, the total movement of the carburetor or throttle body pin needs to match the total movement of the lever at the transmission.
Here’s an example. On a 1968 Barracuda with an A-904, the throttle pressure rod’s connection on the transmission to the upper bell crank is adjusted according to factory specs, and it moves roughly 15 ⁄8 inches from baseline (closed) throttle pressure to maximum (wide-open) throttle pressure. Therefore, for the transmission to receive the correct signal, the item that actuates or pushes the bell crank also has to move a total distance of 15 ⁄8 inches. Fortunately, a 4611 Carter AVS (a 1969 340-ci V-8 original carburetor) pin that the throttle cable and throttle pressure link attaches to moves 15 ⁄8 inches from dead closed to wide-open throttle. However, if you toss on a typical Holley carburetor “out of the box” and have to move the pivot pin to the only hole on the Holley that it fits in, which is farther away from the throttle blade’s shaft, the total movement from closed to wide-open throttle is 21 ⁄4 inches. If you hook the throttle pressure linkage to it, you find it is out of alignment side-to-side and the length is way off. If you are crafty, you make it fit, but it still may not work. The carburetor can be at idle with the throttle pressure link adjusted so the back of its groove hits the pin on the carburetor lever.
A test drive reveals that something is wrong; with the pedal to the floor, it doesn’t seem to have as much power as it used to. The transmission shifts fine at wide-open throttle, but the vehicle feels doggy. You look into the carburetor or throttle body with the pedal to the floor but the secondary is not wide open. Easy enough to fix you figure: reset the throttle pressure linkage so that at wide-open throttle, the linkage aligns with the maxed-out throttle pressure lever on the transmission or at the bell crank. Now you can achieve maximum power because the throttle body or carburetor can go wide open. It runs hard and shifts great at wide-open throttle, but it shifts terrible at light throttle. It slips and shifts way too soft and soon. Why is this? The transmission lever needs only 15 ⁄8 inches total movement for everything to work correctly. Unfortunately, this carburetor pin moves 21 ⁄4 inches with it in the wrong hole (which is the only one t fi t). And here is the most terrible thing done so frequently to the TorqueFlite: “Oh well, no need for kickdown, I’ll just leave the ‘kickdown’ linkage off.”
Here’s how to fi x this. Edelbrock and Holley offer an adapter (the Edelbrock version is PN 8021; Holley’s is PN 20-7) for their respective carburetors for Chrysler applications that holds the pin the right distance from the throttle shaft so that the linkage moves the 15 ⁄8 inches from closed to wide-open throttle. You may have to make a longer throttle pressure link or raise the throttle cable bracket (or both if you use taller intake) to get it correct if yours was a 2-barrel vehicle. By using these adapters, the transmission always receives the throttle pressure signal it needs.
If after the three most basic things (fluid level, manual linkage, and throttle pressure linkage) have been checked and set correctly, you still have an issue, a road test may let you determine what other things are happening inside the TorqueFlite.
If it moves, drive the car or truck in each gear position and feel for any slippage or incorrect shifts. Pay attention to see if shifts are late and hard or early and soft. Notice if the engine “winds way up” in first and then skips Second and goes straight to Direct, or if it’s mushy in a certain gear position.
Read the “What’s on When” chart (end of Chapter 2) before and after the road test to help identify the issues. Here are a couple of examples.
- In all Forward gears, the rear clutch assembly is active. If the vehicle moves okay until it shifts into “D” Direct and then it slips, it could be the rear clutch dropping out, but more than likely the front clutch assembly is slipping. Because you know the TorqueFlite also uses the front clutch for Reverse, place the shifter in Reverse. If the transmission also slips in Reverse, suspect the front clutch because the rear clutch is not used in Reverse.
- If you have Low and Direct but Second gear feels funny or takes a long time to “engage” fully, suspect something in the kickdown band assembly. Why? You know it can’t be the rear or front clutch assemblies because Low and Direct work. When it shifts into Second, the kickdown band is added into the equation. Using the knowledge of how the TorqueFlite works helps narrow down the problem(s).
If you still don’t know what is wrong, the next troubleshooting step can be hydraulic pressure testing to learn what is going on inside.
Hydraulic Pressure Testing
Pressure testing various sections of the TorqueFlite is possible because of the 1/8-inch NPT (National Pipe Taper) pressure ports strategically located on the exterior of the transmission. To test it, I used two pressure-rated hoses with easy-to-read and accurate gauges along with straight and 90-degree 1/8-inch NPT male pipe fittings. A 300-psi gauge is required for Reverse pressure but a 100-psi gauge works for everything else. With a long hose, you can locate the gauge well away from the transmission, eliminating the need to be underneath the vehicle while testing it.
The four 1/8-inch NPT ports enable measurement of line pressure, rear servo apply pressure, front servo release pressure, and governor pressure. By adding a “tee” into the cooler line circuit at the transmission rear cooler line fitting or at the radiator, the lubrication pressure can be checked. These five pressures allow diagnosis of most any stock-type internal failure. As an added bonus, it’s fun to watch the gauges during operation.
Again, be sure the simple things (fluid level, linkage adjustments, etc.) have been checked and corrected before pressure testing. Along with gauges and hoses, a tachometer and a safe way to raise and support the vehicle (preferably a lift) are required. I never recommend doing this on cheap and flimsy jack stands, nor do I suggest lying underneath a car or truck on jack stands while manually shifting the transmission and/or moving the throttle pressure lever. No transmission test is worth your life. Locate the gauges away from underneath and operate the linkages from above. For another level of safety, the rear wheels and tires can be removed.
Pressure in Manual “1” or “L”
This tests the pump, pressure regulation, and the rear clutch and rear servo assemblies.
Connect two 100-psi pressure gauges: one to the line pressure port and the other to the rear servo port. With the engine speed held at approximately 1,000 rpm and the transmission shifted to “1” or “L,” release the brakes so the wheels turn and observe the pressures. Slowly push the throttle pressure linkage from its idle (front) location to its farthest rear location and watch the gauges. The line pressure should start around 54 to 60 psi and increase to 90 to 96 psi, and the rear servo pressure should follow line pressure within about 3 psi. Apply the brakes to stop the wheels before putting the transmission back in “P.”
Pressure in Manual “2”
This tests the pump, pressure regulation, the rear clutch, and the lubrication pressure.
Connect two 100-psi pressure gauges: one to the line pressure port and one to the rear cooler line. You can tee the 0- to 100-psi gauge into the cooler line at the radiator or at the cooler return line on the rear of the driver’s side of the case. With the engine speed held at approximately 1,000 rpm and the transmission shifted to “2,” release the brakes so the wheels can turn and observe/ record the pressure after it shifts into Second gear. Slowly push the throttle pressure linkage from the minimum (front) to the maximum (rear). The line pressure should increase from 54 to 60 psi up to 90 to 96 psi, and the lubrication pressure should increase from 5 to 15 psi at idle to 10 to 30 psi. Apply the brakes to stop the wheels before putting the transmission back in “P.” Even though lubrication pressure should not cause shifting or driving issues, it is the lifeblood of the TorqueFlite, and it is important to see how it acts when the transmission is operating.
Pressure in “D”
This tests the pump, pressure regulation, and the front and rear clutch, along with the lock-up converter circuit (if so equipped).
Connect two 100-psi pressure gauges: one to the line pressure port and one to the front servo release port. Hold the engine speed to about 1,600 rpm and place the selector lever in D, release the brakes so the wheels can turn, and observe the pressure after the wheels rotate and the transmission shifts into Direct. Slowly push the throttle pressure linkage from the front to the maximum rearward travel. The line pressure should have started around 54 to 60 psi and increased from there as the throttle pressure linkage moves rearward. The front servo pressure should read the same as the line pressure (within about 3 psi), up to the point that detent downshift occurs and the transmission kicks down to Second. At this point, the pressure drops to basically 0 psi. Apply the brakes to stop the wheels before putting the transmission back in “P.”
Pressure in “R”
This tests the rear servo assembly. Connect the 300-psi gauge to the rear servo apply port. Place the selector lever in “R,” hold the engine speed to about 1,600 rpm, release the brakes so the wheels can turn, and observe the pressure gauge. The rear servo apply pressure should read anywhere from 160 to 270 psi. Apply the brakes and after the wheels have stopped, move the selector lever to “D” to verify that the rear servo apply pressure drops back to 0 psi.
This test is usually only needed if the transmission shifts at abnormal speeds, even though the throttle pressure is correctly set. The values given are typical for a vehicle equipped with a 2.71 to 3.23 final drive ratio with the throttle pressure linkage hooked up and functioning correctly.
Connect the 100-psi gauge to the governor pressure port on the rear of the case. Place the transmission in “D,” release the brakes so the wheels can turn and the transmission shifts into Direct, and watch the pressure gauge with the speedometer showing 21 to 24 mph. The governor pressure should be around 15 psi. Increase the speed up to 50 to 65 mph and the governor pressure should be around 40 psi. Increase the speed to about 85 mph and the governor pressure should rise to about 60 psi. Apply the brakes to stop the wheels, but leave the transmission in “D.” The governor pressure should drop to zero (at least no higher than 1.5 psi). Place the transmission back in “P.”
This Tech Tip is From the Full Book, CHRYSLER TORQUEFLITE A-904 & A-727 TRANSMISSIONS: HOW TO REBUILD. For a comprehensive guide on this entire subject you can visit this link:
SHARE THIS ARTICLE: Please feel free to share this post on Facebook Groups or Forums/Blogs you read. You can use the social sharing buttons to the left, or copy and paste the website link: https://mopardiy.com/how-to-troubleshoot-a-chrysler-torqueflite-transmission/
Results from Pressure Testing
- If you recorded and/or observed the listed line pressures when the throttle pressure linkage is moved from its forward to its rearward positions, the pump and regulation system are functioning correctly.
- If you observed low pressure readings in “D,” “1,” and “2” but proper pressure in “R,” it means there is a leak in the rear clutch circuit.
- If there were low-pressure readings in “R” and “1” but correct pressures in “2,” it means there is leakage in the rear servo assembly.
- If you observed correct pressure in “1” but low pressures in “D” and “R,” there is likely leakage in the front clutch circuit.
- If you observed low line pressure in every position, it may indicate a clogged oil filter, low fluid, a bad oil pump, or a stuck pressure regulator valve in the valve body.
- If the values observed during the governor tests do not match the suggested values at the correct speeds, there may be a sticking valve or weight in the governor body. The pressures should increase smoothly and proportionately to changes in throttle and speed. With the wheels completely stopped but the transmission still in the “D” position, the governor pressure should not be much above 1.5 psi or it may not downshift correctly. If the throttle pressure linkage is set wrong and it is being pushed rearward even though the engine is idling, it can cause high governor pressure making the transmission stay in a higher gear.
From this sequence of tests, one thing should be very apparent: the transmission absolutely depends upon the throttle pressure linkage for almost anything it does. The throttle pressure linkage has to be right, but if its not the pressures are wrong and things happen at the wrong time and with the wrong force. If there is a gap between the pin of the throttle and the linkage, it can cause runaway or flaring upshifts at light throttle, way too early and too soft upshifts, and possibly no or incorrectly timed downshifts at wide-open throttle. If the linkage is set too far the other way, in other words, it is being pushed, even though the throttle is still closed and the engine is at idle speed, there may be late and harsh upshifts and slamming in gear when the transmission is shifted into Forward or Reverse gears from Park or Neutral.
No Need for Throttle Pressure Linkage?
One thing that becomes obvious when working on hot-rodded vehicles with TorqueFlites is how often people ignore the transmission’s need for correct throttle pressure signals. Because it is such a common occurrence, I believe it was the cause for the failure of the transmission discussed here. The transmission is an A-999 and the oil and filter had recently been changed; it was obvious because of the new gasket. However, the filter was plugged with flakes and metal particles. The transmission had a deep pan, a filter extension, and it had been converted to cable shift. It had mismatched pan bolts and had the line pressure cranked up. The oil pump clearances were perfect. The endplay was fine and all the hard parts looked good. The rear clutch assembly was totally burnt, the kickdown band was discolored and had been hot, and the front clutch friction discs were burnt and the steel plates had hot spots. Clearly, everything had been slipping.
Based on seeing this many times, here is my analysis. The transmission was in a car and the owner put in a floor shifter, a deep pan, and a filter extension. He or she added a new 4-barrel intake and carburetor. The throttle pressure did not fit the new carburetor as it did the old 2-barrel and “because it is only for kickdown,” he or she tossed it. The car shifted soft and started to slip so he or she dropped the pan, cranked up the line pressure, and swapped on a new filter (at least once). He or she continued to drive and hot rod it, but it kept getting worse and slipping more. Likely as not, he or she dropped the pan again and changed the filter one last time, but it was getting filled with black friction flakes and metal particles. The last straw was after the fluid change; it acted the same and would not pull itself. Out came the transmission and it ended up going to the transmission parts supplier as a core.
Would the testing provided in this chapter have identified the problem? Absolutely. Step one is to check the most basic things. The fluid check would have shown that it was getting hot and was filled with particulate contamination. The shifter adjustment was likely okay. However, when the throttle pressure linkage was checked, the answer would have been obvious.
Air Pressure Testing
The previous hydraulic pressure tests provide data to verify the pump is working correctly, that the governor and lubrication circuits are functional, and that they show the integrity of the hydraulic sections. They may not indicate that clutch frictions and steels are completely worn out, that bands are too loose, or that something was put together incorrectly. They do provide valuable information without tearing into the transmission. However, applying air instead of fluid to some sections and using your ears can offer even more clues. Fortunately, some of the key internal hydraulic components can be air tested. Similar to tests after a rebuild, air can be directed into different ports to actuate circuits. The pan and the valve body need to be dropped, but valuable information is provided from the tests.
Where do you begin? Let the vehicle cool before removing oil pan bolts to drain the fluid. The valve body stays hot for a long time; don’t be in a hurry. Remove the filter; while more fluid drains, loosen the pinch bolts holding the shift and throttle pressure levers on the manual lever shaft and remove them. Loosen the 10 valve body (7/16-inch headed) bolts and drop it enough to let fluid drain; it will do so for a long time. When it slows to a drip, remove the 10 bolts and the E-clip from the park rod. Preferably, pull the whole park rod out of the transmission with the valve body by rotating the driveshaft until the rod breaks free from the park pawl assembly. Set the valve body aside in a clean pan.
Front Clutch Test
Use 30 to 40 psi air from a rubber-tipped blowgun and apply it to the front clutch passage (located next to the front valve body bolt hole and the small rectangular pump pressure output port. If everything is okay, you’ll hear a dull thud. If not and there is a lot of air hissing, something is wrong in the front clutch assembly. Likely as not, Drive Direct and Reverse felt odd.
Rear Clutch Test
The rear clutch apply port is next to the front clutch apply port; apply 30 to 40 psi of air to it and listen for a thud; it should not hiss or burble, which indicates an excessive leak. An air leak or no thud may indicate the rear clutch assembly was slipping. In this case, all forward gears may have had problems.
Test This port is between the accumulator piston and the rear servo bore, and air will pressurize the servo. Direct 30 to 40 psi air into it and the servo piston should push out and clamp the band around the low-reverse drum. If it doesn’t work, you likely had issues with Reverse gear or Manual Low felt “funny.”
Kickdown Servo Test
This port is between the accumulator piston and the front servo. Direct 30 to 40 psi air into it and the servo piston should push out, clamping the band around the retainer. If it does not work correctly, you had issues with Second gear.
Air Pressure Test Results
If all air tests indicate the hydraulic portions of the TorqueFlite are correct, and the previous tests did not indicate any malfunctions, something may have gone bad in the converter or the valve body. If the servos pushed out but did not clamp hard on the retainers, recheck band adjustments.
If the history of the transmission is unknown because you just bought it (or the car or truck it was in) and/ or it just never felt quite right, maybe it was put together incorrectly or incompatible modifications were performed. It could be that mismatched parts were used somewhere. Before removing it, there is still one more test that can be made.
Torque Converter Stall Testing
When most rear-wheel-drive vehicles were new, and the parking and service brakes worked correctly, the converter stall test was “relatively” safe. However, after all these years and after brake changes have been made, it may not be as safe. With engine output up to a level higher than ever before, you must be very careful doing this test. Do it only in a safe location with nothing in front; the parking and service brakes have to work correctly. I think it is a mentally difficult test to do unless you have a lot of nerve, great brakes, (and it’s not your vehicle being tested).
This is an “exciting” test and the brakes are held on hard, the tires are blocked, and the throttle is held wide open until the engine reaches a point that it can’t rev any higher. This is where the torque converter “stalls” and it should be done no longer than about 5 seconds. In this test, maximum engine speed is limited by the restriction of the oil flow inside the converter as it is forced through the locked-in-place stator. The test puts engine power (via the spinning converter and its integral impeller) against the stalled turbine, stator, and the transmission that is (hopefully) locked by the brakes holding the rear wheels. As you can imagine, working the oil over with this much sheering force creates a lot of heat, and for this reason, the test should only last a few seconds and be followed by cool-down time in Neutral with the engine at idle.
TorqueFlites have low-stall converters, high-stall converters, and everything in between. Hemis and 340s act one way under stall testing due to their looser, higher-stall converters and 383 2-barrel cars with low-stall converters act another way. Much of this difference is due to the diameter of the converter and the parts inside of it, but the engine torque also affects it. This is why the engine has to be running correctly before testing. Regardless of the engine/vehicle/converter combination, stall testing enables mechanics and owners to verify that the torque converter is still functioning according to the design engineer’s recommendations.
Let’s look at possible outcomes. If the stall speed is above the stated stall RPM, the converter may be incorrect, or the transmission is slipping. However, if the engine can’t reach the factory-stated stall RPM, but the brakes are holding, the converter may be incorrectly matched to the engine, the engine may be running poorly, or the stator’s overrunning clutch inside the converter is slipping or broken completely. If so, the vehicle will feel sluggish at low speeds, almost as if it is in Drive Direct all the time. If, on the other hand, the vehicle accelerates correctly at lower speeds, but at highway speeds the throttle has to be pushed hard, the stator assembly may be locked up. In both cases, the converter has to be replaced.
A sample of the factory-stated stall speeds of many engine and transmission combinations is given in Appendix B.
Unlike manual transmissions, noises from automatics are less prevalent and a little tougher to figure out.
A light buzz that sounds as if it is coming from the center of the transmission is often a check ball vibrating in the valve body or a governor valve buzzing. Dad’s 1969 340 Dart Swinger used to buzz, but engineering changes to the valve body eliminated the problem. Many shift modification kits also address this noise.
Front Section Noise
A louder whine from the front of the transmission is commonly converter-related. There may be something rubbing on the inspection cover/plate that can be fixed by bending the plate and/or tightening loose bolts. The later-year converters may have a needle roller bearing that fails. Lock-up converters can fail and the apply plate may be close to the friction material at the wrong time causing a hiss or slipping sound. The only fix for internal converter issues is replacement.
Knocking noises can occur and, like other issues on older transmissions, they may be caused by someone not following recommended torque specifications. In some cases, the use of different bolts can create interference. Often, wear in the crankshaft’s main thrust bearing can let the crank move front to rear with engine speed and load. The most common knock is where a converter bolt starts to back out, hitting the thin steel inspection cover first and eventually, the back of the block. As the crank moves, the knock may come and go. If the crank bearing has a bit more clearance, the knock may be louder, and if the bolt eventually backs out farther, the knock can be really loud.
A cracked or broken flexplate can create a loud and terrible knocking that sounds as if a rod is about to fly out of the block. In both cases, remove the inspection cover and check the converter bolts and the flexplate.
Damaged teeth in the planetaries can cause gear noises that sound like loud grinding or knocking. This is very serious, and the vehicle should not be driven because metal particles will get into the entire lubrication, governor, valve body, and torque converter circuits. Fortunately, few TorqueFlites damage planetary gears in typical street, mild off-road, or mild strip usage.
Vibration in Floor
A whining/vibration felt and heard is often caused by a bad output shaft bearing. I have seen this most often in truck transmissions, and it gets louder and its pitch increases with road speed. Fortunately, extension housings can be removed and the bearing changed without pulling the transmission.
Knocking in/on the Floor
With oil leaks and age-related wear, rear transmission mounts can fail. When it happens, there may be a banging and knocking noise under the seat or on the floor when shifting from Forward to Reverse or when hitting bumps. The mount can be changed without removing the transmission.
Leaks seem easy but often they turn out to be more complicated. In the bellhousing area, there are many sources of potential leaks and, unfortunately, most of them require you to remove the transmission.
If dealing with a leak, clean the underside of the vehicle at a car wash to pinpoint the source. Pressure wash the lower portion of the engine as well as the fl oorpan surrounding the transmission. Wash around the rear seal and the floor surrounding it to learn if fluid is being spun out by the U-joint. With dual exhausts and headers, this job is sometimes tough on cars and 4WD trucks, but to get an accurate determination requires things be clean enough that leaking fluid can be detected.
An Important Tool to Make
Shop manuals show fabrication of a curved bracket that bolts to the bellhousing and its purpose is to help mechanics decide if oil is thrown off the converter or if it is running out of the pump seals. When dealing with a bellhousing area leak, this tool is invaluable and very easy to make. Fabricate it from a scrap of thin (22-gauge) aluminum, 6 inches long and 1.5 inches wide; a 1/4-inch hole is drilled into it for its attaching bolt.
With the tool on, start the engine, put the transmission in “N” (Neutral), and hold the speed to 2,200 to 2,600 rpm for a couple of minutes. If the tool shows fluid is being spun off the converter, it may be cracked or leaking, or the front seal is spraying fluid on the hub and converter body, which throws all over the inside of the bellhousing. If the gasket between the pump, the pump bolt seals, or the kickdown servo pin plug are leaking, there will be fluid inside the bottom of the bellhousing, but it is not spun off the converter hitting the tool. If the leak is bad enough, it runs out the lower portion of the housing. A cracked case, although not common, can act like a leaky pump gasket and servo plug seal because the fluid runs out, but it is not sprayed on the converter and thrown everywhere. Use of this leak tool helps identify the source.
An Overlooked Weld
I installed an A-727 in one of my cars that had different friction plate quantities and styles, a shift kit, and a different kickdown band. After pulling it a few times to “optimize all my tricks,” it finally felt good. After a few days, I noticed a small leak in the bellhousing area. The starter and the inspection cover/dust shield were removed to reveal most fluid was getting thrown from the converter body. Easy enough; yank it out and change the obviously leaking front seal (after making sure the hub was good and not scarred).
Everything looked fine so in went another new seal. After a day of sitting, it was fine, no leaks. I took it for an easy drive and although not too bad, it still leaked. I decided it must be from the front seal area, so it came out, the pump was yanked, and a new converter hub bushing and seal were installed. It worked well sitting for another day, so I tested it idling in Park. No leaks.
Another test drive and the leak started again. I figured it must be a porous pump so in went another one because pumps were cheap and easy to get. Same thing. After pulling it for the seventh time, it was time to think and read. The shop manual had many suggestions regarding sealing the case and blowing air into it, as well as sealing the converter and doing the same. It showed a simple tool to make to determine where a leak was coming from but I chose to ignore it. I never considered that maybe the converter builder had missed something. Looking over his welds, they looked fine. The drain plug was dry so I decided to air check it, even though I knew it had to be fine. I poked a hole in the protective polyethylene plastic cap that comes on the hub and pressurized the converter. Sure enough, there was an almost invisible leak in one of the welds. Darn it.
I now know that when the converter was filled and under pressure, it spit fluid out. Under high load, in gear, it was far worse. In idle, it never seemed to do much, but remember, idling in Park does not tell you much because the converter is not charged the same as it is in Neutral or any Forward or Reverse gear. Had I been able to lie underneath it and watch it under stall conditions, it would have been spitting a lot more fluid out. Had I made that recommended tool immediately, I would have negated the need to yank it so many times. Welding the pinhole shut took the local converter builder a few seconds.
After everything is as clean as possible, verify that the fluid level is correct; an overfull condition can force whipped-up fluid out of the pump vent and then onto the converter. If you have an older TorqueFlite with the small inspection cover/dust shield that unbolts to allow access to converter bolts, remove it and look or feel inside the bellhousing with the engine off. The starter can be removed to get the complete inspection cover off so the leak’s origin can be found. If there is lot of fluid in the bellhousing that was not removed, wipe or rinse it out.
In summary, if there is a leak in the front area, it could be a bad converter, oil pump seal and/or bushing, oil pump gasket, oil pump bolt seals, kickdown servo lever shaft plug, a cracked or porous case, or fl uid being spit out of the breather. An older converter may have a drain plug; it too must be snug and sealed. Other than correcting the fluid overfull condition, all of these require pulling the transmission to repair.
You may be lucky and have only a bad O-ring on the dipstick. Older TorqueFlite dipsticks (pre-1969), bolt on by the pan area, but later ones were held on with one of the transmission-to-engine bolts. Remove the dipstick, replace the O-ring, grease, and reinstall it.
A large potential leak is from the pan gasket. There are many varieties, but most common are cork gaskets. A paper-based gasket is included in some filter and overhaul sets, and these seem a bit more difficult to keep sealed. I have torn many transmissions apart that had an excessive amount of RTV-type silicone on the pan bolts and gasket, and worst of all, it was inside the pan and on the filter. If the pan is flat and came with a gasket, there is never a reason to use this type of sealer (later transmissions often used no gasket and required sealer). For TorqueFlites that require gaskets, a high-quality cork gasket torqued to factory specifications (150 in-lbs) will work well for several years. The bolts may require a tweak after driving the vehicle, but they should stay leak-free for a long time.
A Way to Fix the Seal
To access the seal, the throttle pressure and shift selector levers need to come off so the valve body can be dropped. With a four-wheel-drive truck or car with headers, it will be tough to get to the levers. Once the valve body is out, drive the old seal out with a flat screwdriver or punch. Buy a couple of seals (one for a spare) and get two flat washers that are larger than the seal. You will use a 3/8-16-inch nut and a 1.5- to 2.0-inch-long, 3/8-16-inch bolt to sandwich the seal between the washers and the case. Put some RTV-type silicone sealer around the circumference of the seal and then place it on top of the case opening. Place a bolt through the top of the washer, through the seal, and the case. From the bottom, install another washer and nut. Tighten the nut (while holding the bolt) a small amount at a time to pull the seal into place. Stop if it does not pull straight in. Retry it. Use the spare if you bent the first one. After it is in nice and flat, grease it, and reinstall the valve body and levers.
There were some cork gaskets with metal cores that lasted a long time and could be reused, but they have disappeared. The Chrysler dealers and aftermarket suppliers now offer replacement plastic or metal cored composite gaskets with a silicone or urethane rubber seal pattern (imprinted on both sides) that work very well.
Shifter Shaft Seal
A leaking shifter shaft seal is a bit tougher to replace, but it can be done in the vehicle. This leak seems to occur more often when the car or truck sits for long periods of time. This makes sense because the fluid accumulates in the pan when the pump is not sending it everywhere during operational conditions. With the area clean around the top of the shifter shaft, the leak can be identified quickly.
Speedometer Adapter O-Ring and Internal Seal
If the speedometer cable is removed from the adapter and fluid runs out the end of the cable and adapter housing, chances are high that the internal lip seal is bad. If fluid is leaking around the body of the adapter, the O-ring may be shot. Either way, it is easy to pull the adapter and replace both. Make a note of the orientation of the adapter in the extension housing. Put the lip seal back in the adapter with the lip facing the inside, grease the gear shaft, put the new O-ring around the outside, and grease it before putting it back in the extension housing.
Rear Band Anchor Pin
This one, if leaking, is more difficult and requires a lot of work to fix. Go to the appropriate section in Chapter 5 and Chapter 8 for specifics, but a summary is that the extension housing has to be removed, the valve body pulled out, the low-reverse band loosened, and the pin pulled out from the rear so the O-ring can be replaced. I have seen somewhat successful repairs where the leaky area is cleaned with solvent and then a large amount of silicone sealer is put on the pin and the case surrounding it. It looks bad, but it often works for a while.
Extension Housing, Bolts and Bearing Snap-Ring Cover Plate Gasket
The extension housing gasket could be leaking, but I have never had a bad one. If yours is, remove the housing and replace the gasket, and while you are there, replace the bearing snap ring plate’s cork or paper gasket. You should replace the rear seal too. Sometimes, bolts holding on the extension housing may seep. If yours looks damp, put a bit of RTV-type silicone on them before reinstallation.
This can be replaced with the extension housing on the transmission, but look closely at the rear bushing and driveshaft yoke because they could be damaged enough to wear the bushing and take out the seal. Push up and down on the driveshaft with it in the transmission and see how much slop there is. New ones have very little but if yours wobbles a lot, the bushing is likely worn and needs to be replaced. There is a tool to do it with the housing in place. If the bushing is worn out, remove the housing and visit your local transmission shop if you don’t have the bushing driver. Install a new seal with a bit of RTV-silicone sealer around its circumference. Often, time and miles just wear out rear seals and this may be the only thing wrong with it. New types of elastomeric materials are better than they used to be, so it’s not unusual to have an original type seal that seeps or leaks a little now and then.
Diagnosing new, unspoiled, and unmodified TorqueFlites must have been a bit more straightforward back then. No doubt, unexpected engineering changes and technical service bulletins caused complications, as they do today. Now, with the passing of years and changes made by several owners, figuring out what makes TorqueFlites underperform or fail can be a mystery. If performing all of the tests in this chapter offers no concrete solutions, you may just have to remove it, go through it, and put it back like it used to be.
Written by Tom Hand and republished with permission of CarTech Inc
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