4l80E loses TCC twice in one month?

[damork]

On a couple of occaisons in the last month I had my truck hunting in and out of TCC lockup. I could shut down and restart and it was gone. I have high miles, but this tranny has been babied and never above 175-180f, and has had regular flushes and filters.

I talked to an ATRA/ATSG tranny shop and they were ready to do a full rebuild on the spot saying the torque converter oring is leaking so might as well rebuild it, so I backed away from them. They haven't done diagnostics on it.

Has anyone found other causes such as TM solenoids or TCC solenoids to be the culprit in these? It really doesn't make sense that much could be wrong but I could believe the valve body / solenoids could be a reasonable starting point. It's been over a week since it last acted up, otherwise I've had solid lockup.

[markrinker]

Rebuild it. (KIDDING!!!)

Good transmission shops are hard to find. Believe it or not, I have found my local Chevy dealer as a good source of info on diesel transmissions, since many of them find their way back to the 'factory' service department.

I'd check with them and focus on the torque converter itself, NOT the transmission based on your description.

[whatnot]

Does it happen to do it down hill with the cruise on?
Mine has done it ever since I changed the injection pump.

[Bill Voitel]

If you can get to a trans shop while it's acting up to get it scanned B-4 shutting it down to see if it is setting a code it sounds like it's re setting itself after shutdown. 4l80e is a pretty tough unit with proper service(like yours has had)some of them get a lot of miles but sol's are prone to fail......good luck


Bill.

[eracers999]

If the torq converter is going down then you should have had a shudder condition at some point. With your maint that condition would be unlikely. Get it on a scanner and moniter the voltage inputs to the tcc and the over drive. Check for any codes. If none are present then go to the engine menu and pay attention to the coolant temp sensor input, if it looses conection the tranny will react by canceling tcc and over drive because it will think that the temp is minus 40 deg. Do not tear that tranny out until you have diagnosed it, if all is well electricly and the converter is bad it will log a code for tcc slip. How is reverse and hi gear shift?? Those 2 shift points are they shifting just like they used to?? GM has a updated drum for the 3rd gear it is prone to cracking. When that drum has a issue it really shows up on rev, 3rd and tcc lock up. If your problem is intermittant then chances are it is not mechanical, it is a solonoid problem that should show pretty easy on a good scanner.
Hope this helps you.
Kent

[damork]

Thanks for all the replies.

With respect to the TCC unlocking going downhill, it doesn't. This was happening on flat terrain, in fact I thought it was going to be a simple diagnosis as long as it repeated.

I have considered replacing the solenoids at this stage and updating the valve body if the AFL bore is worn (using some Sonnax fixes). I will definitely have a diagnostic run on it before going into it and prefer to as much as I can myself.

I'm suspecting issues mentioned like intermittent signals or solenoid issues - maybe poor grounds. Other than the two times the TCC was hunting, the lockups have occurred right on time and at 48-50 mph. All shiftpoints including the TCC lockup are firm and I've been looking for slip but can't seem to detect any - in fact all shifts are as they should be. I'm going to check codes as that is easy but there have not been any lights. The tranny fluid temps have been running 120-150F lately while ambients are 60-75F.

I agree, I'm very paranoid about finding a good shop - regardless how many certifications are listed. Sometimes I think shops just want to yank and rebuild. I've been spending money upfront to avoid a rebuild after a bad experience with a 700R4 behind a 6.2 diesel (7 rebuilds in 7 years). I know 4l80e units are solid, and some have over 300k without major rebuilds.

[Diesel Dan]

Long story short.
The converter in my '00 was bad by 90K. Would drop out of OD and TCC intermitently and didn't set a code until about the 6th time I had it. Truck did minimal towing before I had it and fluid was clean and no junk in the pan. Installed a tow converter and trans-go 4L80E-HD2 valve body kit with Mobil 1 trans fluid.
All is good now.

Now the 4L80E in my '91 mechanically lost 4th gear with 20K on a GM SRTA :( .