4L80E TCC Cycling Solutions?

[damork]

My 95 4L80E is up to no good with a cycling TCC circuit. Cruising 55-60 it will pop in and out of lockup and does not seem to care if it is cold or warm.

It does have high miles, but easy ones with regular doses of new fluid and flushes, filters and Lubeguard. I've also added a 12V relay for power supply to the trans instead of via the ignition switch. Pan temps never exceed 180F.

Trans shops I talk to are not as much in the diagnosis mode as they are ready to do a complete rebuild, and I'm not convinced it needs it, but want to know a bit more. No codes either.

Is this common and if so, is there some common culprit or not? I'm chasing down grounds and connections already but nothing showing up.

[charliepeterson]

This isn't a common issue as far as I remember. It could be a bad TCC solenoid in the pan. This one is on the front of the valve body. The other two in the back are the 1-2 and 2-3 shift solenoids. These are real easy to swap out. The two on the outside are the input and output speed sensors.

With no codes the ECM is getting the correct feedback but the performance is still off, so it could be a lazy solenoid valve. These transmissions are really good.

[eracers999]

Put a scanner on it and monitor brake switch activity, need to eliminate the easy stuff first.

Kent

[Marty Lau]

Originally posted by Kent:
Put a scanner on it and monitor brake switch activity, need to eliminate the easy stuff first.

Kent Damork;
Sorry to hear your woes, I hope you figure it out, I feel close to you as I have used your posts in the past to help me. (cooling upgrade)
I have had a 2 diffrent guys tell me that bad brake switch can cause problems so either do what Kent says or just chang it out. I changed all the stuff inside the pan on my transmission a while back when I had a problem and it's not too tough. AllData has some touble shooting stuff for the tranny on it too. If you want old solenoids and valve body I have the old ones, my problem turned out to be a wiring issue. (I think)
I did notice when I changed everything in the tranny that it shift better.

[diesel65]

Damork,
Do you have a trailer connector out back, 7-way?
Inspect the connector for corrosion (green stuff)
A friend of mine had similar issues with his transmission, he found his connector all corroded, he removed the old connector then cleaned the wires and installed a new connector, now the truck runs good.

What I think was happening is the corrosion is allowing stray voltage from the charging wire to feedback thru the brake light circuit and the computer is picking it up, and that would cause the convertor to unlock. (My Theory)

[damork]

Wow - thanks for the info! The brake/wiring circuit you mention really makes sense and hadn't even considered it, and I do have a corroded trailer wiring plug. Guess I'll be exercising a VOM this weekend if I don't find a shop with a proper trans scanner. It has to be something simple as it acted up a year ago for a few days then stopped before I could find it.

[damork]

diesel65

Thanks, -your post on the corroded trailer connector seems to hit home. I bought a new brake/tcc switch anyway and will replace it as PM plan (only $10), but the trailer connector was a mess - rusted and green. I could not even read the codes because of poor connections, jumpering the diagnostic port would result in a steady light and no flash.

I R&R'd the connector, sealed the new one with anticorrosion inhibitor and cleaned up (recleaned) several grounds and the TCC cycling seems to have stopped.

[donr]

I had the same problem. This sounds funny, but it turned out to be a bad connector on the temp sensor on the top front of the engine. I replaced the sensor while I was at it, but it was just the wire pulled loose making an intermittent connection. Works like new now. The sensor is just for the transmission shift control, I guess.

[LanduytG]

Trailer wiring would have to be shorted out for it to be a problem. One thing I have found is a dirty plug on the trans itself.

Greg

[diesel65]

Greg,
The wiring does not have to be shorted to cause a problem.
The corrosion is conductive and it will pass voltage from any source in the trailer connector, whether it come from the charge line or the turn signals or the park lamps, any stray voltage backfeeding where it don't belong can cause problems.