GM 6L80 Transmission Information Thread

[NickTransmissions]

So with those two gallon jugs that I just posted, why does only the one say Full Synthetic?

My guess (and that's literally what it is as i really dont know) is that the first label simply assumes the customer already knows Dex6 is full syn or its perhaps sold only to dealership and/or other service centers while the second one is labeled for general retail sale and is labled so everyone knows it's synthetic and not conventional fluid.

 

[alpha_omega]

One is the newer logo. That’s the only difference. They still sell the older stuff because they have it on the shelves. Other than that…no difference at all.

 

[NickTransmissions]

Updated the OP w/the first vid in a new series dedicated to troubleshooting, testing and diagnosing these transmissions...More videos to come in the coming days and weeks!

 

[Geotrash]

Thank you, Nick!!

 

[NickTransmissions]

Thank you, Nick!!

You're welcome, Dave!

 

[strutaeng]

@NickTransmissions I started watching your videos. That's some great information to share. Thank you.

I own several GMT800s and rebuilt few 4L80e units. I bought an Express passenger van my wife daily drives. It's a 2020 and has around 12,000 miles with the 6L90e. I have a few questions for you if you don't mind:

1. Was the torque converter ever improved from GM on late production units? Doesn't sound like it? At what mileage should you recommend to replace it?

2. Is there an aftermarket torque converter you recommend?

3. What can be done from a maintenance perspective to help prolong the life of the 6L80/90? On the LS1TECH forum there's a member that was previously one of the Hydramatic engineers for GM. IIRC, he recommended fluid changes at 25,000 miles for this transmission.

4. Do you also recommend the modification to the ECU tune that limits TCC slippage? Seems like a common modification with the HP Tuners crowd, although I don't really know the details. I think there's something related to AFM that also gets modified on vehicles that had it?

5. The cooler thermostat bypass delete kit seems like a good idea since it will minimize the chance of overheating?

I may attempt to rebuild a 6 speed in the future, mostly to learn about them. They seem like cool units. I just need a big stash of cash for tools, a core (later model seems better?) and a rebuild kit.

Thanks in advance.

 

[NickTransmissions]

@NickTransmissions I started watching your videos. That's some great information to share. Thank you.

You're welcome, man and thank you for the kind words...I'll be putting out more vids on these units over the course of the next few weeks - please subscribe if you haven't done so already
Here's my responses in red:

1. Was the torque converter ever improved from GM on late production units? Doesn't sound like it? At what mileage should you recommend to replace it?
Not that I'm aware of - same design throughout the production run (06-21)

2. Is there an aftermarket torque converter you recommend? I'd go with any reputable converter builder who installs a .050+ converter clutch (my builder uses Borg Warner .070" high energy converter clutches) as well as offers billet covers as the two most common problem areas are that clutch and warpage in the covers. Yank, Circle-D, TCI, Florida Torque Converter. There's many more but those come to mind.

3. What can be done from a maintenance perspective to help prolong the life of the 6L80/90? On the LS1TECH forum there's a member that was previously one of the Hydramatic engineers for GM. IIRC, he recommended fluid changes at 25,000 miles for this transmission. Yep, VortecIROC - he and MaroonMonsterLS1 were both GM powertrain engineers and agree with their advice 100% (I say 25k-35k is a good cadence).

4. Do you also recommend the modification to the ECU tune that limits TCC slippage? Seems like a common modification with the HP Tuners crowd, although I don't really know the details. I think there's something related to AFM that also gets modified on vehicles that had it? Many of my customers tune out the TCC apply in 1st-4th gear and only have it come on in the two overdrive gears as having it work so hard in part-throttle stop and go driving stresses it more than it saves in terms of heat reduction. Speaking of which (see below)

5. The cooler thermostat bypass delete kit seems like a good idea since it will minimize the chance of overheating? Absolutely - run that kit or flip the pill (youtube has several vids on the procedure and I'll do one as well if I can grab a complete CBV assembly out of the yard.

Hope that helps!

 

[SpyShops212]

Nick when my 10 speed fails do you work on them? How good are they and how many miles should the 10 speed last. On my 2008 Speed Escalade my transmission failed at 155k. Is the 10 speed better made and will it last longer. My truck is babied. I never peeled out & changed my fluid and filter at the dealer on time.

 

[NickTransmissions]

Nick when my 10 speed fails do you work on them? How good are they and how many miles should the 10 speed last. On my 2008 Speed Escalade my transmission failed at 155k. Is the 10 speed better made and will it last longer. My truck is babied. I never peeled out & changed my fluid and filter at the dealer on time.

Hi @SpyShops212 , I'm not super familiar with them, haven't gone hands on with one yet but have researched them (and the 8speeds) as I may take one or both transmission families on in the near future. From what I understand, the 10-speed has some improvements that address some of the pattern failures seen in the 8L45s/90s but like all transmissions, will have it's share of warts.

Are you located in or around Vegas?

 

[Charlie207]

If I were to replace the torque converter with a better-than-OEM aftermarket unit, would I notice it in day to day driving, or would it just be a reliability upgrade?