4t60e TCC problem?

[willyman82]

Hi All,

I have a 1995 Chevy Corsica with the 3100 and 4t60E transmission.

At highway speeds under even the slightest load like going up a hill it feels like it has no power (TCC still engaged?) then it feels like it might be slipping somewhere then suddenly grabs and goes. There is no tach so I cant really tell very well what the engine is doing. I have read about a lot of different TCC problems with these transmissions (stuck TCC valve, leaking TCC valve, bad TCC solinoid, bad PCM TCC solinoid driver or a bad vacume pressure actuator). Is there anyone with enough expertise to help me differentiate between possible problems? I thought it was the 4 gear clutches so I "shotgunned" a transmission with 51K into the car. I changed a bunch of other stuff while I had the motor out so it wasnt so bad. It was working great for about 2 weeks, but now the same old problem is back, which invalidates all the other work if I cant nail this problem.

Other things that I replaced before doing the transmission were engine position sensors, TPS, FPR, fuel filter, plugs and wires. I have not replaced the MAP and have read that this helps the PCM determine engine load for unlocking the torque converter. I am going to check this out with a DVM and hand-vac this weekend.

Thanks for any help!

[3400-95-Modified]

If you did have a bad map then I think you would be noticing many more issues... and a 1995 corsi IIRC the TCC stuff goes by throttle position and speed, not engine load.

If you've replaced the entire transmission then I can tell you that the TCC valve, TCC solenoid, the PWM solenoid, and the vac regulator are fine, Unless you swapped all those parts onto the new trans from the old... Which I doubt you did.

Next in line is the converter itself. Did you re-use your original one when you swapped transmissions?

[willyman82]

Converter, valves and vacuum actuator came with "new" 51K mile transmission. I changed the fluid when I did the transmission. I dont have a flush tool. I just filled it up after the swap, cranked it for about 30 seconds with one of the cooling lines off, topped off, repeat, until I went through 2 gallons of fluid. So the fluid that is in there isnt perfect but it was coming out clean to begin with. I would think that if there was a major issue with the car that it came from, then the original fluid wouldnt be so clean. I did not change the filter. I was going to let it go 3000 miles to the next oil change then do the transmission fluid again after letting it wash through the whole transmission and the filter at that time.

Some more detail:
When I put the shifter into D (assume 3rd gear) the engine revs higher and I can feel when the TCC locks up. It doesnt unlock until well after 1/2 throttle at which point it seems like it is slipping while releasing, almost like a half hearted release. This is the same sensation as when in OD, except I can feel it more because the gear ratio is higher. This shudder happens around 1/4 throttle when in OD. I dont know if this means the valve could be sticking when the PCM is trying to release it or if there is a line pressure problem (holds stronger at high RPM). There are no codes in the computer, but I dont think the computers checked for these types of problems in 95. The trans came from a granny-mobile, so I doubt it ever saw much of the torque converter locking up around town. The torque converter was not discolored or rusted at all. The old one looked like it had been sitting in an annealing oven for 2 years, rusted and discolored. Also, it doesnt stall or even shudder when downshifting or coming to a stop.

I hope the level of detail is more helpful than it is annoying.

[robertisaar]

the "slipping release" is exactly what it should do, due to the PWM TCC. it's intended to do just that.

[willyman82]

The way I understand TCC opperation is that it is supposed to progressively lock up (PWM apply) under light load, then hold until a certain threshold is reached, then it is supposed to just let go under higher load (a hill on the highway). And the problem is that it never actually lets go. I havent confirmed with a meter+test drive yet, but I would bet the computer is still holding the TCC engaged when I feel this pulsing/slipping sensation. When I feel the slipping, I can either let off and it stops (assume TCC remains locked), or press the pedal to the floor then it unlocks and the car actually goes. So it seems that it isnt holding hard enough near the threshold of where the PCM would normally command it to release. The interesting thing that I discovered in today's experiments is that it seems that 3rd gear has a higher power threshold before I encounter the problem, but it still exists. Driving around in 3rd isnt so great for gas milage.

The more I think about it, the more I think the computer may be trying to hold it too long (an attempt to improve milage by GM) or there is an apply line pressure issue.

I found this:

http://www.transmissionpartsusa.com/SC_4T60E_1_transmission_reconditioning_kit_1997_up_p/400-0sc4t60e1.htm

http://www.sonnax.com/instructions/SC-4T60-E-97-IN.pdf

Thanks,
-William

[robertisaar]

The more I think about it, the more I think the computer may be trying to hold it too long (an attempt to improve milage by GM) or there is an apply line pressure issue.

that notion is pretty relevant to almost all settings in the ECMs made by GM... but the PCM does release the TCC in a PWM fashion, just like TCC lockup, though with that type of slipping/pulsing, it's possible that the convertor itself is toast...

[gpse3400]

I agree that it could be the converter if you are still using the old one. Another trick you can do, cut the wire for the PWM soleniod and see how it operates then. The apply will be more noticable and the converter should hold harder. If you still have the problem, I would lean on the converter being bad....providing you did not change it prior.

[willyman82]

I used the "new" 51K miles converter with the trans swap. I tend to think that it isnt the converter, because when its in 3rd the problem doesnt happen until well after 1/2 throttle. So if it was a problem with the converter, I would expect it to slip with the same amount of torque applied from the engine. 4th gear at 1/4 throttle (75MPH) is probably less torque applied than 3rd gear at 1/2 throttle (75MPH).

GPSE3400: Could you please specify which solenoid you are referring to?

I dont understand all of the ins and outs of the trans, but is it correct that the converter will still lock up without the solenoid powered? I thought the solenoid actually drives the valve that locks and unlocks the converter, as opposed to just regulating the operation. This trans has a vacuum cylinder that controls operating pressure instead of a PWM solenoid like newer transmissions.

Thanks,
-William

Edit: One of my friends told me that there are two things in automatic transmissions, ATF and magic. Maybe I just forgot to add the magic back in...

[robertisaar]

in 3rd with 50% throttle, yeah, more torque, but less load.

the convertor will NOT lock if the TCC solenoid isn't getting power.

[payback]

ive had identical issues with my 4t60....its possible the TCC solenoid itself is bad, even on the newer tranny. very common.
but im under the impression the valve is stuck, yes the solenoid is supposed to actuate the valve, but if its stuck its stuck.
mine actually threw a code (TCC solenoid lockup stuck on) but mine is obdII.
the problem mysteriously went away but every once in a great while it comes back, but not nearly as bad or as long..which tells me its more of a "somethings stuck" problem rather than an "its bad" problem.

[3400-95-Modified]

The more common issue that a bad solenoid on a 4t60e is the valve getting stuck itself.

The solenoids go bad on 3t40' but for a 60e, the way to fix this is getting the Shift Correction kit installed, It adds a spring on the return side of the TCC valve, and also makes you chamfer every edge of the valve itself to prevent hang up.

I don't have pics right now of the fix, but I'll be pulling my trans apart soon and I'll show you what they make you do to a stock valve. I will also be replacing the stock one with a Sonnax repair valve, Those have a Teflon seal on them to help prevent any TCC issues later down the road.

I had really bad TCC problems once and the issue that I ended up having was my roll pin that holds my center shaft in my diff snapped off because the outer spiders were galled to the pin... One wheel burns will do that... with a 60e the pin can't fall completely out.. It will sit there spinning around slowly scoring a mark all the way around the outside of the diff housing which in turn spreads aluminum through the motor... in doing that, almost ALL of my valves ended up getting stuck, or started sticking from the aluminum flakes in the oil. It was BAD when I took it apart. I had to replace the valve body completely.

[gpse3400]

I used the "new" 51K miles converter with the trans swap. I tend to think that it isnt the converter, because when its in 3rd the problem doesnt happen until well after 1/2 throttle. So if it was a problem with the converter, I would expect it to slip with the same amount of torque applied from the engine. 4th gear at 1/4 throttle (75MPH) is probably less torque applied than 3rd gear at 1/2 throttle (75MPH).

GPSE3400: Could you please specify which solenoid you are referring to?

I dont understand all of the ins and outs of the trans, but is it correct that the converter will still lock up without the solenoid powered? I thought the solenoid actually drives the valve that locks and unlocks the converter, as opposed to just regulating the operation. This trans has a vacuum cylinder that controls operating pressure instead of a PWM solenoid like newer transmissions.

Thanks,
-William



Edit: One of my friends told me that there are two things in automatic transmissions, ATF and magic. Maybe I just forgot to add the magic back in...

The PWM Soleniod for the TCC flakes out very often on the older transmissions. when it does it can cause the TCC to engage poorly or not at all. By disconnecting it the main TCC soleniod will have controll over the circuit. I'm not sure what wire it is, you will need to get a wiring diagram. Just cut the wire or remove the pin and drive the car. The problem should go away. Keep in mind the TCC will engage more noticably.

[robertisaar]

this should help with the wiring... brown wire in the tranny connector. and if you can happen to see the lettering on the connector, it's position C.

if you need the diagram for the plug itself, i'll have to upload that too...

[willyman82]

This is all good info. One thing that is still conflicting is whether or not the TCC will lock up if I cut the connection to the TCC solenoid. I was under the impression that it will NOT lock up if power is cut. The wiring diagram that I have shows that the power for the TCC solenoid comes from a switch on the brake pedal that is intended to shut it off when stopping. This would imply that cutting any wires will cause the TCC to not lock up. The diagram that robertisaar uploaded doesnt align with the diagram I have for my 95. Maybe later 4t60e's had more stuff in them? My diagram shows only 3 solenoids with no temperature sensor. I measured to all of the pins on the connector of the old transmission. I get 48 ohms between two circuits with a common pin (suspect these two are the shift solenoids). Then 10 ohms between two other independent pins. I suspect this is the TCC solenoid. All other pins appear to be open circuits on the old transmission. I still have to test the new one to see if I get the same results. Does anyone know what these resistances are supposed to be?

The "new" trans came from a car with 51K that was a 95 Cutlass I think... There is no way the donor car saw a lot of highway time with the TCC locked, so I am struggling with the concept of how anything could have worn out related to the TCC hydrolic circuit.

More testing will happen this weekend...

[3400-95-Modified]

The TCC locks up ALL THE TIME, not just on the highway so its not uncommon for it to wear out even if driven by a g-ma. Its more the act of town driving and 45-50mph where its locking and then unlocking... At least its like that in my area because we have lots of hills.

95 4t60e's had the temp sensor as well. I have a 94 trans in my 95 beretta thats run by a 97 venture ECM and I can read a trans temp value, and I've seen it with my own eyes.