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.
Rough Steels
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.
Fluid Level
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.
This filter did its job; the size of metal particles and friction material flakes it caught range from microscopic to 1/16 inch in diameter.
Your first step should be to check the fluid level. This one is down a pint, probably due to a pan gasket leak.
Adding type 7176 Mopar fluid brings the level to the lower part of the range.
Shift Linkage
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