Tranny Troubles.

[blazes9395]

First , this is not for my trucks, but rather for my '95 monte carlo. recently (past couple of months on and off), I completly rebuilt the 4T60e tranny in this car. Everything back together, all is well but I am getting a P0740 every so often. I have done all the updates, the TCC on/off valve, TCC regulator, enlarged TCC oil supply hole on the valve body plate, new electronics etc, etc. I have found that this problem has been found by rebuilders, as the sonnax tech articles document this problem. I took this car to the dealership to see what can be done for any computer updates, I was told nothing because it is not a VCM, but its an older ECM, with the chip inside it. i don't understand that, as these can be updated too. Its a PWM tranny. I can honestly say i am stumped at this one. Main line pressure is good in all gears, its right on spec. It shifts good and it works well, it only trips the po740 rarely. It will do it warm, and even cool oil temperatures. My scanner does not have the ability to scan TCC slip percentage, PWM duty cycle percentage. Does anyone have any ideas, or information regarding this problem? Thanks

[BlazerLT]

Have you actually replaced the solenoid yet?

[blazes9395]

Originally Posted by BlazerLT

Have you actually replaced the solenoid yet?

Yeah, I replaced all the electronics, PWM solonoid, shift solonoids, TCC on/off solonoid, the only thing I have not changed is the actual internal wire harness.

[BlazerLT]

So what happens when this failure occurs?

Is it just a light coming on or is their some driveability issues?

[blazee]

Originally Posted by BlazerLT

So what happens when this failure occurs?

Is it just a light coming on or is their some driveability issues?

It would be hard to tell because the setting of the code should cause hard shifts and the loss of 4th gear.

Originally Posted by blazes9395

Yeah, I replaced all the electronics, PWM solonoid, shift solonoids, TCC on/off solonoid, the only thing I have not changed is the actual internal wire harness.

I did a little searching and it seems to be a fairly common problem with the 4T60-E, even the ones that haven't been rebuilt. It looks like the most common causes are the solenoid itself, the wiring, and the PCM. Here's some related info, it's from a Pontiac with a 4T60-E, but may be helpful.




Circuit Description

In conjunction with the Torque Converter Clutch Pulse Width Modulation Solenoid Valve (TCC PWM Sol. Valve), the Torque Converter Clutch Solenoid Valve (TCC Sol. Valve) controls the fluid acting on the TCC converter clutch valve. This controls the TCC apply and release. The PCM monitors the throttle position, the vehicle speed and other inputs in order to determine when to energize the TCC Sol. Valve. Circuit 439 supplies ignition voltage directly to the TCC Sol. Valve. The PCM controls the TCC Sol. Valve by providing the ground path through circuit 422. When you command the TCC Sol. Valve OFF, the PCM receives high voltage. When you command the TCC Sol. Valve ON, the PCM receives low voltage. If the PCM detects low voltage when the TCC Sol. Valve is commanded OFF or high voltage when the TCC Sol. Valve is commanded ON, then DTC P0740 sets. DTC P0740 is a type A DTC.


Conditions for Setting the DTC

• The ignition is ON.
• The System voltage is 10-16 volts.
• The engine speed is greater than 500 RPM.
• Not in fuel shut-off.
• The PCM commands the solenoid valve ON, and the voltage remain high (B+).
• The PCM commands the solenoid valve OFF, and the voltage remains low (0 V).
• All conditions are met for 5 seconds.

Action Taken When the DTC Sets

• The PCM inhibits TCC operation.
• The PCM inhibits 4th gear, if the transmission is in hot mode.
• The PCM illuminates the Malfunction Indicator Lamp (MIL).

Conditions for Clearing the MIL/DTC

• The PCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
• A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.

• The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.

Diagnostic Aids

• Inspect the wiring for poor electrical connections at the PCM. Inspect the wiring at the transmission 7-way connector. Look for the following conditions:

• A bent terminal
• A backed out terminal
• A damaged terminal
• Poor terminal tension
• A chafed wire
• A broken wire inside the insulation

• When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.

Test Description

The numbers below refer to the step numbers on the diagnostic table.
6. This step isolates the fault between the engine harness and the transmission harness.
8. This step verifies that circuit 422 is not open or shorted to power.
12. This step verifies that the TCC Sol. Valve is not shorted across its windings or increased its resistance.

[blazes9395]

LT: yes, it by default shifts only up to 3rd gear and it will not lock up the TCC, and the shifting is bad, no adaptive shifting strategy used.

Blazee: yes thanks for taking the time to find that one. I did a search and found this information too this morning, and am now in the process of going through it. I also have additional information from ALLDATA too, some diagnostic flow chars etc. The diagram looks more useful than what I found on the ALLDATA site, so I'll be printing this one....thanks again. Now its off to the garage....again.

[blazes9395]

Well, its been awile since I started this thread, and again thanks too all who threw in their suggestions. After a while of literally pulling my hair(I'm alright in this department-for now anyways), I decided to pull the tranny and take it apart again , go through it again. So after I got it out opened it up and once inside, took the valve body off, and UNBELIVIABLY found my problem - I can't believe I missed this one. I found the turbine shaft was not aligned properly to the channel plate bushing, in other words the TCC apply oil was exhausting past the sleve and not getting to the TCC to lock it up. Upon further inspection, I found the retaing ring(a .25 cent piece) broke and allowed the turbine shaft to float around the bore, causing all these problems. Went to the tranny parts place, got a used turbine shaft, replaced the seals on the shaft, new retaing ring, put it all back together, and presto- TCC lock-up like butter. I can't beleive it- I couldn't literlally do anything else these past couple of months because of this problem, it has been eating me up. I now have been able to sleep better at night since it has been fixed. I could have taken it to a shop, and they would have easily found the problem, that would have meant I would have given up, and well, I don't easily, very, very, very rarely give up on things, so the bastard is done.

My point to posting this, as it may or may not help anyone in this forum, is to ALWAYS take a look at the simple, most general things to solving problems before letting your mind get ahead of you. Usually when this happens it costs you more, and only frustrates the crap out of you. (as it did me and $200.00 wasted dollars) The good old K.I.S.S. Just a little food for thought...

[BlazerLT]

Thanks for the update.

You have some balls ripping your own tranny apart.

[blazes9395]

Thanks LT, yeah trannies can be intimidating, but with a little research, and a lot of reading, theya re like any other part on a vehicle - just a little bigger. Besides, I have had some experience on trannies before, so that helped a little.

[BlazerLT]

For sure, I wouldn't EVER touch it without any basic knowledge.

[blazee]

Originally Posted by blazes9395

Thanks LT, yeah trannies can be intimidating, but with a little research, and a lot of reading, theya re like any other part on a vehicle - just a little bigger. Besides, I have had some experience on trannies before, so that helped a little.

Thanks for posting the conclusion.

You rebuilt the tranny in the 95 Blazer that you had too, didn't you? Any pictures of the new Blazer?

[blazes9395]

Yeah, did the '95, have done a couple 700R4's,(identical except the electronics), and have helped with a few when I worked at a garage. Yeah, I did say I would post a couple, I will, I just need to get out there and snap a few, actually I plan on throwing a couple of pictures of both my trucks. Its too dark right now, I'll get something on here tomorrow.