GM 6L80 Transmission Information Thread

NickTransmissions · Sep 24, 2024

DamThatRiver24 said:
6l80 here (2010 Tahoe LTZ). Have heard from a lot of folks (including a few on here) that 30-35k is the severe schedule that we should be sticking to on these transmissions.

For me, that's about once a year, lol. Is it your opinion that it could probably go another 20k each cycle and be fine?

The figures in the post you quoted was for daily drivers, crusiers and mild performance applications. HD/Serious work, severe off-road, HP/SS, full race and other non stock applications will require more frequent fluid changes, common sense right?

If your usage pattern fits the above, every 30-50k somewhere in there is recommended. More severe the duty, more frequent the fluid service.

Sgt1411 · Sep 25, 2024

My 2007 Escalade has the 6L80E transmission. (6-SPEED AUTOMATIC, HEAVY-DUTY, 6L80E, ELECTRONICALLY CONTROLLED) The transmission was apparently rebuilt a few years back and has absolutely no fluid leaks anywhere. Checking fluid shows it is red and full no signs of discoloration. The vehicle has around 168,000 miles on it but only one owner before me and I knew him so I know the history. The vehicles runs very well but I had a question about drivability characteristics and perhaps its just me not understanding those dynamics with this older transmission.

If your driving along at 30-40MPH and your slowing for a red light so you let off the throttle. The light goes green before you come to a full stop so now you apply throttle and there is a second or two delay and then a bit of a clunk like the transmission was in the wrong gear and had to drop down a gear. Is that a normal behavior or indication of something?

NickTransmissions · Sep 25, 2024

Sgt1411 said:
My 2007 Escalade has the 6L80E transmission. (6-SPEED AUTOMATIC, HEAVY-DUTY, 6L80E, ELECTRONICALLY CONTROLLED) The transmission was apparently rebuilt a few years back and has absolutely no fluid leaks anywhere. Checking fluid shows it is red and full no signs of discoloration. The vehicle has around 168,000 miles on it but only one owner before me and I knew him so I know the history. The vehicles runs very well but I had a question about drivability characteristics and perhaps its just me not understanding those dynamics with this older transmission.

If your driving along at 30-40MPH and your slowing for a red light so you let off the throttle. The light goes green before you come to a full stop so now you apply throttle and there is a second or two delay and then a bit of a clunk like the transmission was in the wrong gear and had to drop down a gear. Is that a normal behavior or indication of something?

Is this issue new or has it always behaved this way? If the latter, for how long?

donjetman · Sep 25, 2024

@Sgt1411

search "clunk" and/or "Klunk" on this forum.

motor mount(s), front diff mount(s), transfer case worn chain.

CTX-SLPR · Sep 26, 2024

Nick,

Is there a place you can buy a preassembled pump and bellhousing? Local guys seem to have gotten out of the game of doing job work so looking for a contingency plan if the pump is damaged when I pull the trans apart for testing and a Zip Kit. I can find new ones in knock down kit form but without the test tool to see if the vanes are too tall a preassembled one seems like a better bet.

Thanks

tkdgirl · Sep 30, 2024

So this is probably going to sound like a dumb question but let me give a little bit of back history.

My transmission blew in July replaced with a new one direct from GM. GM had to reprogram the TCM which meant the custom tune I had was out of sync. Therefore a ton of bad clunking and downshifting. When I had the original custom tune flashed again it got better but the clunking is still there primarily at slower speeds or when I have to make a sudden stop from over 50 mph.

The past week the weather's been great so I haven't been using my AC. No clunking.

What could be going on with the AC that would affect the transmission?

When the transmission blew I was towing in tow mode and had the AC on.

@NickTransmissions I honestly don't know what to do at this point.

Sgt1411 · Oct 2, 2024

NickTransmissions said:
Is this issue new or has it always behaved this way? If the latter, for how long?

Since I have owned it, this is the driving behavior.

Approximately 12-15 months, isn't getting worse just the same.

I'm just interested to know from a subject matter expert if this is a normal characteristic of these trucks or something needs replacing

Sgt1411 · Oct 2, 2024

donjetman said:
@Sgt1411

search "clunk" and/or "Klunk" on this forum.

motor mount(s), front diff mount(s), transfer case worn chain.

Thank you

NickTransmissions · Oct 2, 2024

Sgt1411 said:
Since I have owned it, this is the driving behavior.

Approximately 12-15 months, isn't getting worse just the same.

I'm just interested to know from a subject matter expert if this is a normal characteristic of these trucks or something needs replacing

This can be normal as the transmission/TEHCM/PCM has a split second uncertainty as to exactly what the vehicle is doing between the time you let off and the time you reengage the throttle so it's making split second decisions on what gear you need to be in based on all that data streaming into the THECM/PCM. If it's happening all the time and the shifts become overly harsh then that would indicate problems, either in the torque converter, transmission or both.

I'd suggest taking for a test drive with your bidirectional scan tool plugged in and live transmission and torque converter data displayed so you can spot any anomalies in the PIDs. If so, begin your diag from there.

NickTransmissions · Oct 2, 2024

tkdgirl said:
So this is probably going to sound like a dumb question but let me give a little bit of back history.

My transmission blew in July replaced with a new one direct from GM. GM had to reprogram the TCM which meant the custom tune I had was out of sync. Therefore a ton of bad clunking and downshifting. When I had the original custom tune flashed again it got better but the clunking is still there primarily at slower speeds or when I have to make a sudden stop from over 50 mph.

The past week the weather's been great so I haven't been using my AC. No clunking.

What could be going on with the AC that would affect the transmission?

When the transmission blew I was towing in tow mode and had the AC on.

@NickTransmissions I honestly don't know what to do at this point.

The AC system (specifically the compressor) places some marginal load on the engine as it's working so it's possible that's throwing off the tune, though not likely since tunes would account for that. Bear in mind, this is a guess on my part as I'm not a tuner and have no experience working with vehicle programming software. I'd consult your tuner or whichever company made your tune to see what they have to say. Sorry I can't be of more help with this one.

GM 6L80 Transmission Information Thread

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