OT Any 4L80 E GM automatic transmission xperts around here?

moonlight machine · Dec 30, 2016

About 10 or 12 years ago I swapped the Turbo 400 3 speed automatic transmission in my dualy for a 4L80 E 4 speed overdrive transmission with a stand alone aftermarket computer to control it. Totally trouble free for many years it started acting up about 2 years ago. It sticks in low gear once every 2 months or so. Sometimes cold, other times after driving 100 miles. It stays in low for 1-3 miles or so then starts shifting fine again. So far I have changed the fluid and filter, the shift solenoids, and the shift computer. The thing does not stay broken so it's not easy to sort out. Ideas anyone?

Street · Dec 30, 2016

Most if not all electronic controlled transmissions do not have a mechanical governor, they read the input and output speed sensors and throttle position sensor.

so other than a build up of black carbon junk inside it blocking the shuttle valves etc, look in those places.
dirt in the throttle sensor, loose wires, bad adjustment to chopper wheel.

Some transmissions start in 2nd gear, only time they use first is in kick down ( full throttle position ) its a little hard to pick the gears sometime, be careful with that.

They are complex things so pick one item then go through it and move to next item a process of elimination which will take time.

Monarchist · Dec 30, 2016

moonlight machine said:
About 10 or 12 years ago I swapped the Turbo 400 3 speed automatic transmission in my dualy for a 4L80 E 4 speed overdrive transmission with a stand alone aftermarket computer to control it. Totally trouble free for many years it started acting up about 2 years ago. It sticks in low gear once every 2 months or so. Sometimes cold, other times after driving 100 miles. It stays in low for 1-3 miles or so then starts shifting fine again. So far I have changed the fluid and filter, the shift solenoids, and the shift computer. The thing does not stay broken so it's not easy to sort out. Ideas anyone?

Erratic electrical connector is a published possible, but I'm sure you have been there already.

Highly respected box in its day. Adopted by Bentley, Rolls Royce, Jaguar, Aston-Martin...

No relation to the ZF's utilized since, but those of us afflicted with similar "random acts of confusion" have generally found it takes THREE successive hot flushes of ZF Lifeguard to get the last cowering bit of hidden tramp debris out.

I'd surely try the equivalent multiple-flushing before pulling it for teardown or upgrade.

Bound to be other uses for the 'squandered' ATF around the shop, some requiring filtering, others not.

On-edit: I keep readers in the console, can attach, read and clear all the codes when my ZF goes bug-f**k. Hard shift 2-3.. which can trigger something else, etc. We also have to have the 'self learned' adaptive shift patterns our controller stores reset to square one periodically. Bugger tends to 'learn' bad habits now and again.

Does your custom aftermarket controller help you with those codes?

Bill

wmcm · Dec 30, 2016

Good flush usually does help. I've had this happen with a bad ground connection also. Being that its erratic at best sounds electrical imho.

alonzo83 · Dec 30, 2016

when I was a kid my dad had bought a 95 Chevy turbo diesel with that same problem from the factory it would get stuck in 2nd. he traded it off for a Toyota before the problem was solved. You need to seek out a chevy truck forum. It is a well known problem dating back 20 years now.

cvairwerks · Dec 30, 2016

Sounds just like the 4L60E in one of my trucks. Under 45 deg F. or so, it will not come out of first gear for about the first half mile, then starts shifting fine until it is parked and cooled off to ambient temp. I've been told that there are 2 o'rings in the back of the pump system that get hard and do not seal correctly until the warm up some and get pliable again. The fix requires a complete tear down of the transmission. By the time you by the parts and do all the work, you can buy a well done, dyno checked unit from Monster(?) for a little bit more money.

moonlight machine · Dec 30, 2016

cvairwerks said:
Sounds just like the 4L60E in one of my trucks. Under 45 deg F. or so, it will not come out of first gear for about the first half mile, then starts shifting fine until it is parked and cooled off to ambient temp. I've been told that there are 2 o'rings in the back of the pump system that get hard and do not seal correctly until the warm up some and get pliable again. The fix requires a complete tear down of the transmission. By the time you by the parts and do all the work, you can buy a well done, dyno checked unit from Monster(?) for a little bit more money.

The thing is mine does it at random, hot or cold. I used it 3 times yesterday with no trouble till the 3rd time, It was about 1/2 hour after I last used it when it did it again.

Bill D · Dec 30, 2016

How often have you done a full transmission flush? Not a drain and refill but a pull the hose run the engine, full exchange. My wife's Ford escape people recommend 30,000 miles.
Bill D.

dkmc · Dec 30, 2016

I hate to be a snake oil salesman, but a buddy with a
Saturn was having similar problems.
He put in 2 bottles of Trans-X and the problem went away.
Something about swelling the seals & O rings and dissolving the varnish that makes the valve spools stick.
Didn't even change the fluid and filter.
It's like $10 a bottle........could it possibly hurt to try it?

moonlight machine · Dec 30, 2016

dkmc said:
I hate to be a snake oil salesman, but a buddy with a
Saturn was having similar problems.
He put in 2 bottles of Trans-X and the problem went away.
Something about swelling the seals & O rings and dissolving the varnish that makes the valve spools stick.
Didn't even change the fluid and filter.
It's like $10 a bottle........could it possibly hurt to try it?

That stuff actually works in some cases, The old GM 3 speed autos used to get real slow to go in reverse especially when cold, a bottle of that stuff and it was good as new for a year. when it started to act up again another bottle would cover up the issue again.

Monarchist · Dec 30, 2016

moonlight machine said:
That stuff actually works in some cases, The old GM 3 speed autos used to get real slow to go in reverse especially when cold, a bottle of that stuff and it was good as new for a year. when it started to act up again another bottle would cover up the issue again.

"Cover up" is the operative phrase.

More than one Buick Dynaflow - and many a newer box as well - has limped rather long miles home on ignorant tapwater, too.

But that don't make it right. 10 or 12 years in on this box?

Even if low miles, there's age and weather-change degradation. OVER due for sumthin'.

Then again, is the vehicle over it due for replacement as well?

Bill

dkmc · Dec 30, 2016

moonlight machine said:
That stuff actually works in some cases, The old GM 3 speed autos used to get real slow to go in reverse especially when cold, a bottle of that stuff and it was good as new for a year. when it started to act up again another bottle would cover up the issue again.

I say give 'er a chug, and report back.....

bridgedog · Dec 30, 2016

I know a 700 R 4 will tow a trailer 150 miles on gator-aid! Blew a hose out in the middle of nowhere and only liquid was said drinks. I don't think a can of trans-fix would have helped it afterwards but it did get me home :crazy:

moonlight machine · Dec 30, 2016

Monarchist said:
"Cover up" is the operative phrase.

More than one Buick Dynaflow - and many a newer box as well - has limped rather long miles home on ignorant tapwater, too.

But that don't make it right. 10 or 12 years in on this box?

Even if low miles, there's age and weather-change degradation. OVER due for sumthin'.

Then again, is the vehicle over it due for replacement as well?

Bill

400,000 on the truck 250,000 on the trans. It's due for replacement for sure. Only cost about 60,000 to get new one.....Not a chance in hell. I'm 60, how much longer will I need a dualy? 15 years if I'm lucky? This is probably the last truck I'll own.

converterking · Dec 30, 2016

Change the 2 speed sensors, they are cheap and easy to change. Next would be the tps. What brand controller are you using? I wish you were closer, I have 2 transmission dyno's and all the electronic testers for these transmissions. You could also pull the valvebody and replace the separator plate and checkballs.I replace these on every transmission. Check that there arent any stuck valves. That is about all you can do without removing the transmission and overhauling it.

Chip Chester · Dec 30, 2016

I have a Tech2 that may give you insight on sensor functions. Aftermarket controller might be a curveball, though.

Chip

trevj · Dec 30, 2016

alonzo83 said:
when I was a kid my dad had bought a 95 Chevy turbo diesel with that same problem from the factory it would get stuck in 2nd. he traded it off for a Toyota before the problem was solved. You need to seek out a chevy truck forum. It is a well known problem dating back 20 years now.

There is a transmission sub-forum on Dieselplace. I got a lot of good info there when I had mine.

Short version. Grounds. All of them. Plus as many as you can adapt to ensure power gets through.

I bought mine with a known 'weak' tranny. Ended up installing one I bought from a fellow whose project was being parted out. It had been rebuilt by a competent shop, and he had spent rather more on it than I ended up paying.

LOTS of little things that can go sideways in one of those trannys. Only takes one bad Oring or sketchy solenoid to screw it up.

Cheers
Trev

Garwood · Dec 30, 2016

I would look for a used late model 4L80E and swap it out. The newest ones have less problems.

Monarchist · Dec 30, 2016

Garwood said:
I would look for a used late model 4L80E and swap it out. The newest ones have less problems.

A proper rebuild from a reputable shop, yes.

Used would be more of a service history mystery and dice-roll than his own one that he has had sight-of for ten-plus years.

Plus - online info indicates it was succeeded by the 6L80 & 6L90 within a year or three of his one being installed. So his would be a 'late' 4L.

On-edit: Novak, whom I have greater trust in, sez it stayed in production to the 2009 MY.

Bill

moonlight machine · Dec 30, 2016

Garwood said:
I would look for a used late model 4L80E and swap it out. The newest ones have less problems.

If that thing comes out I'll rebuild the original turbo 400 and slap a Gear Vendors over drive on it.

OT Any 4L80 E GM automatic transmission xperts around here?

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