6L80E Transmission Failure

BlackRain · September 4, 2012

Here's the story....

2010 Suburban LTZ 4x4 with 33,000 miles and the 6L80E transmission. (Has never towed anything.)

Last Thursday, I was merging onto the highway, doing about 50 and accelerating up to speed, when the engine redlined, but only because the transmission slipped. No noise, no clunk, no bang, just slipped. I got off the highway at the next exit and came to stop. Tried to move, and at 1500 rpm, it slipped again. Once I got rolling, it would shift, but only when speed was built up a bit. It slipped (in every gear), but not until rpms exceeded about 1500. Limped to the dealer the next morning (it was late), and they checked the codes - nothing. Fluid was red (not brown) and full. No leaks, no sounds, no error codes, no smells. Tranny temp was 140F. Everything seemed normal...

Talked to the service guy today, he indicated that they need to overhaul the transmission and replace the 1 through 4 clutches. It'll probably be a week before it's fixed.

I'm not impressed. What's more, I'm not convinced that the clutch replacements will fix the root cause, i.e., future failures to come. This is not something that just "happens". One bad clutch, maybe. Four? Not likely.

Thoughts? (Aside from trade it in before the warranty's up.)

Carder09 · September 4, 2012

From what I hear, them tranny's are tough. Not sure why yours went so early but nothing is ever built the same. Butif you are ready to trade it in then once its fixed, go nuts.

MikeNH · September 4, 2012

First failure I've heard of on here honestly.

uh6tdrvr · September 5, 2012

First I have read about. There are A LOT of guys putting A LOT of power through them too. Google

brainpause · September 5, 2012

Maybe only one clutch was defective, but it is best to fix all of them while trans is disassembled. Ida know.

BlackRain · September 5, 2012

Would it slip in all gears if only one or two or four clutches were bad...?

brainpause · September 5, 2012

Yeah, I thought of that, too. I don't know. Just throwing my idea out there. Maybe someone can answer that.

Doug_Scott · September 5, 2012

Generally gears are attained by applying clutches and bands that are attached to planetary gearsets. By applying certain clutches or bands certain parts of the planetary gears are either held stationary, or are driven. I can't see one clutch being used in all gears, if there was, they would just pin that part in place.

The dealer may also just be telling you that they will do them all to prevent you from asking why they are not going to do them all. Once they get it apart, they may find friction material through out the transmission and cooler. If it were me, and I had to disassemble all the parts to check their condition, I would be replacing seals in all clutch packs, and all rings in band servers and accumulators. Those parts are cheap. Clutch packs (friction and steels) need to measured and checked for flatness as well. When the clutch slips, it generates a large amount of heat in the discs.

aflesch · September 6, 2012

The clutches in a 6L80E are as follows: 1-2-3-4, 3-5-REV, 4-5-6, 2-6, 1-REV. The numbers indicate what gear they are applied in. So yes, there is one clutch that is applied in 1st, 2nd, 3rd & 4th. Clutches don't wear out after 33k without being caused by some other failure. If they don't find the root cause you will have the same problem again very shortly.

CKNSLS · September 6, 2012

Don't rebuild that one, get a factory one. I would assume the factory one would come with a 12,000 mile warranty, but don't know for sure.

newdude · September 6, 2012

Don't rebuild that one, get a factory one. I would assume the factory one would come with a 12,000 mile warranty, but don't know for sure.

Not 100% sure if a 6L80/90 is a new service replacement, but if it is not, it would be a GM SRTA (Service Remanufactured Transmission Assembly) backed with a 3 year, 100k mile warranty.

Doug_Scott · September 6, 2012

Don't rebuild that one, get a factory one. I would assume the factory one would come with a 12,000 mile warranty, but don't know for sure.

Not normally the customers call on what repair they do under warranty.

Doug_Scott · September 6, 2012

The clutches in a 6L80E are as follows: 1-2-3-4, 3-5-REV, 4-5-6, 2-6, 1-REV. The numbers indicate what gear they are applied in. So yes, there is one clutch that is applied in 1st, 2nd, 3rd & 4th. Clutches don't wear out after 33k without being caused by some other failure. If they don't find the root cause you will have the same problem again very shortly.

Ok, so no one clutch pack is used for all gears then. They will have to do a lot of looking to find the cause if the seals are still good. But, it is very possible the seal was nicked or not installed properly originally. Hopefully they find the cause easily.

BlackRain · September 6, 2012

I was told (a few days ago) the truck would be ready today or tomorrow. We'll see. (I will update when I get it back in terms of what they did.)

Yeah, my concern is that they're only treating the symptoms / outcome of a problem that will cause the failure to repeat. (I'm also concerned that when they put it back together, new issues will arise because, after all, rebuilding these trannys requires extreme attention to detail with no margin for error.)

In terms of warranty, the truck is only 2-1/2 years old, so it should still be covered for another 2-1/2 years. Not going to hit the 100,000 mile mark in that time. (Still, don't want to be stuck 100 miles from home at the side of the highway.)

(Doug - do you work in the 'shwa)?

Doug_Scott · September 6, 2012

I was told (a few days ago) the truck would be ready today or tomorrow. We'll see. (I will update when I get it back in terms of what they did.)

Yeah, my concern is that they're only treating the symptoms / outcome of a problem that will cause the failure to repeat. (I'm also concerned that when they put it back together, new issues will arise because, after all, rebuilding these trannys requires extreme attention to detail with no margin for error.)

In terms of warranty, the truck is only 2-1/2 years old, so it should still be covered for another 2-1/2 years. Not going to hit the 100,000 mile mark in that time. (Still, don't want to be stuck 100 miles from home at the side of the highway.)

(Doug - do you work in the 'shwa)?

No, I was a mechanic before the career ending back injury 20 years ago. I was the transmission mechanic at a Plymouth/Chrysler dealership in Peterborough.