GM 6L80 Transmission Information Thread

[89Suburban]

I agree w/the shop in that putting a new TC on a 197k trans isn't the best way to go...

At 197k, I'd yank it out for overhaul if you are in good position, financially and logistically to have the work done now. If you want to save money and you have a 2WD, you can pull that 6L80 out yourself in about a half hour-40 minutes. Just make sure you're on a level surface, vehicle on all four jack stands (6 tons each) and something to lower and raise the trans back into position (most use a floor jack though you can buy a trans jack which makes the job a lot more efficient).

Alternatively you can drive it until it croaks but may do some damage to hard parts...The major hard part that you don't want to do damage to is the rear planetary carrier set, which is a Ravigneaux design and can be somewhat expensive to replace. The torque converters are pieces of ***** and must be replaced with a converter that features a clutch that's at least .050" (my stuff gets a .070 thick Borg Warner high energy converter clutch, except for real HP stuff which sees a multi-disc converter w/a billet cover. So next time you talk to him, find out what converters he uses and how thick the converter clutch is that comes inside.

I'd also consider replacing your radiator unless it has been replaced within the past 50k or so (buy an OEM GM part, no aftermarket radiators) - the last thing you need is for the internal transmission cooler to fail and leak water into the case under high pressure. That would be catastrophic and require you to literally order a brand new transmission (or find another core and rebuild that one). Flush the lines also (shop will do this if they are doing the removal and reinstallation).

I'd say it's highly unlikely your current transmission was swapped at any point in the past but anything is possible.

Thanks Nick!

 

[NickTransmissions]

I have a 2012 Tahoe at 96k miles should i have the dealer do a reverse flush or change filter and fluid instead?

Drop the pan so you can see what's at the bottom of it and the condition of the fluid and filter....The filters can sometimes crack at the neck though you'd know it if that was the case with yours...nevertheless, it's good to get eyes-on when it comes to that stuff...From there you can flush or just do a partial fluid change...The best way to go is to drop the pan first, then assuming nothing concerning is observed, replace the filter (or if yours is 'ok', re-use it) but I'd cut the old one open to see if anything is in there that shouldn't be (larger bits of metal, bushing material, etc).

Then give it a full flush/reverse flush.

 

[blackelky]

Drop the pan so you can see what's at the bottom of it and the condition of the fluid and filter....The filters can sometimes crack at the neck though you'd know it if that was the case with yours...nevertheless, it's good to get eyes-on when it comes to that stuff...From there you can flush or just do a partial fluid change...The best way to go is to drop the pan first, then assuming nothing concerning is observed, replace the filter (or if yours is 'ok', re-use it) but I'd cut the old one open to see if anything is in there that shouldn't be (larger bits of metal, bushing material, etc).

Then give it a full flush/reverse flush.

Alright thanks. I'll change the filter myself and then take it for the full flush later. Unless you're near Jersey you can do it lol

 

[NickTransmissions]

Alright thanks. I'll change the filter myself and then take it for the full flush later. Unless you're near Jersey you can do it lol

Haha, nope - I'm in Vegas...Sounds like a good plan.

 

[89Suburban]

Haha, nope - I'm in Vegas...Sounds like a good plan.

How far are you from the speedway? My boy Larson #5 won there last weekend. NASCAR Cup series playoffs.

 

[DaveO9]

I agree w/the shop in that putting a new TC on a 197k trans isn't the best way to go...

At 197k, I'd yank it out for overhaul if you are in good position, financially and logistically to have the work done now. If you want to save money and you have a 2WD, you can pull that 6L80 out yourself in about a half hour-40 minutes. Just make sure you're on a level surface, vehicle on all four jack stands (6 tons each) and something to lower and raise the trans back into position (most use a floor jack though you can buy a trans jack which makes the job a lot more efficient).

Alternatively you can drive it until it croaks but may do some damage to hard parts...The major hard part that you don't want to do damage to is the rear planetary carrier set, which is a Ravigneaux design and can be somewhat expensive to replace. The torque converters are pieces of ***** and must be replaced with a converter that features a clutch that's at least .050" (my stuff gets a .070 thick Borg Warner high energy converter clutch, except for real HP stuff which sees a multi-disc converter w/a billet cover. So next time you talk to him, find out what converters he uses and how thick the converter clutch is that comes inside.

I'd also consider replacing your radiator unless it has been replaced within the past 50k or so (buy an OEM GM part, no aftermarket radiators) - the last thing you need is for the internal transmission cooler to fail and leak water into the case under high pressure. That would be catastrophic and require you to literally order a brand new transmission (or find another core and rebuild that one). Flush the lines also (shop will do this if they are doing the removal and reinstallation).

I'd say it's highly unlikely your current transmission was swapped at any point in the past but anything is possible.

Thank you, Nick. Mine is 4wd, but the trans removal doesn't scare me too much. I pulled the 4L80e from my 91 burb without too much trouble. Have one of those scissor lift style trans jacks from HF. Getting the y-pipe out of the way may be the most challenging part.

The shop quoted me a full rebuild for $6700 + WA tax. Too rich for my blood at this time. They do put in all the goodies, I'm confident about that, and build their own upgraded converters. I'd go GM, Jasper, or Precision reman units before I do that, though. Also might consider buying a wrecked truck with lower miles, use the trans with upgraded converter and sonnax upgrades. (I also want to re-gear from 3.08 to 3.42, so I'd look for one with the lower ratio) Part out the rest.

One question I have about the GM and other remans. They seem to all come with converters included. But everyone says the OEM converters suck. Has GM upgraded, or can you get an upgraded one included?

 

[NickTransmissions]

Thank you, Nick. Mine is 4wd, but the trans removal doesn't scare me too much. I pulled the 4L80e from my 91 burb without too much trouble. Have one of those scissor lift style trans jacks from HF. Getting the y-pipe out of the way may be the most challenging part.

The shop quoted me a full rebuild for $6700 + WA tax. Too rich for my blood at this time. They do put in all the goodies, I'm confident about that, and build their own upgraded converters. I'd go GM, Jasper, or Precision reman units before I do that, though. Also might consider buying a wrecked truck with lower miles, use the trans with upgraded converter and sonnax upgrades. (I also want to re-gear from 3.08 to 3.42, so I'd look for one with the lower ratio) Part out the rest.

One question I have about the GM and other remans. They seem to all come with converters included. But everyone says the OEM converters suck. Has GM upgraded, or can you get an upgraded one included?

You're welcome, Dave.

Yes, getting the vehicle high enough for Y pipe removal is the key there...

Here's my advice when it comes to remanufactured transmissions vs shop rebuilds: If you have a shop local to you that is competent and well-versed in those transmissions AND they are willing to go over what they do to the transmission (parts and procedures) AND their pricing is in line w/what you'd otherwise pay from a big-box retailer like Jasper or GM as if they also installed the same upgraded parts into their units (which they don't in most cases) then I'd take the shop-rebuilt 6L series transmission ANY DAY OF THE WEEK over a generically spec-ed out reman with minimal to no performance upgrades, unless you're able to specific exactly which upgrades you would like installed and the big box reman company will do it. The TC can be bought separately from the transmission so just acquire one that is built properly (.050-.070 thick high energy converter clutch element).

The GMs and Jaspers of the world offer very few a la carte upgrade options for individually purchased transmissions because that would mean variability and arbitrary uniqueness in their production models...The more models they have to manage and keep running well, the higher the costs the prod and op-ex they will incur and hence, the lower the bottom line. Small, local shops don't have that problem as it's a completely different business, cost flow and pricing models that lends themselves to customer-specific rebuilds. If by 'Precision' you are referring to Richard Crich, he's an independent shop who will do anything you want done to the unit (AFAIK, he's back in business in a new shop in Amarillo but not 100% sure on that).

Off the top of my head, the two primary reasons folks might go with a reman from a large manufacturer is warranty period (often 2-3 years instead of the typical 12 months) and ease of acquisition - you just go to the website or call on the phone, pay and they send it out - no need to engage in dialogue w/shops which can be a pain point for many folks if the shop is staffed with retards or buffoons. GM has a third benefit in the form of its nationwide service center network which is convenient for folks that need to make warranty claims, they can go to the local dealer to get it dealt with.

The shop's $7.6k figure (assuming it includes R&R, line flushing, cooler cleaning and all the standard upgrades/updates that should be installed into those transmissions) is on the higher side of ball park for what you'd expect for a complete trans rebuild and reinstallation. A GM trans is something like $4000-4500 plus another $1200-1500 or so to stab, fill w/fluid and re-set the adapts plus all the other stuff mentioned. So roughly $6000 but the trans just has the stock level parts and any updates from GM (which in many cases is minimal). It will take another grand or so in Sonnax updates to bring the trans to spec plus another couple hundred for a converter...In the end, it works out to roughly what the independent shop would do and cost, give or take a hundred or two...

 

[DaveO9]

You're welcome, Dave.

Yes, getting the vehicle high enough for Y pipe removal is the key there...

Here's my advice when it comes to remanufactured transmissions vs shop rebuilds: If you have a shop local to you that is competent and well-versed in those transmissions AND they are willing to go over what they do to the transmission (parts and procedures) AND their pricing is in line w/what you'd otherwise pay from a big-box retailer like Jasper or GM as if they also installed the same upgraded parts into their units (which they don't in most cases) then I'd take the shop-rebuilt 6L series transmission ANY DAY OF THE WEEK over a generically spec-ed out reman with minimal to no performance upgrades, unless you're able to specific exactly which upgrades you would like installed and the big box reman company will do it. The TC can be bought separately from the transmission so just acquire one that is built properly (.050-.070 thick high energy converter clutch element).

Thanks much, Nick! You are very generous with your time in answering questions like mine. I will definitely be keeping your advice in mind. Fortunately I am not in a big hurry since everything is running fine, knock on wood. Unless that changes, I probably won't be doing much on this till spring. I think I will do a pan drop and filter change in the near future, though. And I also should have mentioned this earlier - I will have a local tuner do his magic and turn off AFM, and prevent TC lockup in 1-4. Along with some other things. He did the same thing for me on my '09 with 6L80. All that sound OK?

 

[NickTransmissions]

Thanks much, Nick! You are very generous with your time in answering questions like mine. I will definitely be keeping your advice in mind. Fortunately I am not in a big hurry since everything is running fine, knock on wood. Unless that changes, I probably won't be doing much on this till spring. I think I will do a pan drop and filter change in the near future, though. And I also should have mentioned this earlier - I will have a local tuner do his magic and turn off AFM, and prevent TC lockup in 1-4. Along with some other things. He did the same thing for me on my '09 with 6L80. All that sound OK?

Yep, some of my customers do the same. Just keep trans temps in check and all will be well (it will run better since torque multiplication isnt being cut off in gears 2-4 so soon before the engine has a chance to get into the power band (other than at much higher throttle angles where it shouldn't be locking up anyways...)

 

[blackelky]

Thank you, Nick. Mine is 4wd, but the trans removal doesn't scare me too much. I pulled the 4L80e from my 91 burb without too much trouble. Have one of those scissor lift style trans jacks from HF. Getting the y-pipe out of the way may be the most challenging part.

The shop quoted me a full rebuild for $6700 + WA tax. Too rich for my blood at this time. They do put in all the goodies, I'm confident about that, and build their own upgraded converters. I'd go GM, Jasper, or Precision reman units before I do that, though. Also might consider buying a wrecked truck with lower miles, use the trans with upgraded converter and sonnax upgrades. (I also want to re-gear from 3.08 to 3.42, so I'd look for one with the lower ratio) Part out the rest.

One question I have about the GM and other remans. They seem to all come with converters included. But everyone says the OEM converters suck. Has GM upgraded, or can you get an upgraded one included?

Gm has a performance 6l80e for 4700 standard is 3400 on the website. Might save you some at the dealer to price match. Also some chevy dealers have different shop rates the 2 by me are 165 and hour and the other is 220 or something.

 

[dillpickle1]

on a fairly unrelated note, I am planning on buying a 6l80e swap kit for my hummer, are there any mods I should do? It comes with a decent amount of mods like 27 spline output shaft, machined tailhousing for the T-case, modified TCM and a billet Torque converter, the company does offer upgrades to increase the HP rating

 

[NickTransmissions]

on a fairly unrelated note, I am planning on buying a 6l80e swap kit for my hummer, are there any mods I should do? It comes with a decent amount of mods like 27 spline output shaft, machined tail housing for the T-case, modified TCM and a billet Torque converter, the company does offer upgrades to increase the HP rating

Are you planning to add mods/upgraded parts the transmission yourself or have someone else such as the seller/retailer do them? How much power will your engine be putting out and how will you be using the vehicle apart from just driving it around on the street (off-roading, heavy duty use, etc)?

You can take a look at page one of this thread for some ideas on what you should do for strength and reliability beyond just what the factory calls for...

 

[dillpickle1]

Are you planning to add mods/upgraded parts the transmission yourself or have someone else such as the seller/retailer do them? How much power will your engine be putting out and how will you be using the vehicle apart from just driving it around on the street (off-roading, heavy duty use, etc)?

You can take a look at page one of this thread for some ideas on what you should do for strength and reliability beyond just what the factory calls for...

just a L92 out of a Denali, so 400hp minus 1000lbs of weight on the trans, the seller has a 650hp, 750hp and a 1000hp package, I'll probably email them on what they do to it

 

[blackelky]

Drop the pan so you can see what's at the bottom of it and the condition of the fluid and filter....The filters can sometimes crack at the neck though you'd know it if that was the case with yours...nevertheless, it's good to get eyes-on when it comes to that stuff...From there you can flush or just do a partial fluid change...The best way to go is to drop the pan first, then assuming nothing concerning is observed, replace the filter (or if yours is 'ok', re-use it) but I'd cut the old one open to see if anything is in there that shouldn't be (larger bits of metal, bushing material, etc).

Then give it a full flush/reverse flush.

When they did the flush the trans fluid when cold is at the hot mark on trans dipstick. Should I make them take some out?

 

[NickTransmissions]

When they did the flush the trans fluid when cold is at the hot mark on trans dipstick. Should I make them take some out?

Is any fluid belching out of the vent tube on the top of the trans? If no, then no need to bother. If yes but the amount is relatively small, let it vent till it stops. That vent circuit was designed in to enable the transmission to relieve itself from a mild overfull condition.

 

[petethepug]

Thanks Nick. If everyone knew you were in Vegas then we’d all be planning honeymoons, week long getaways and excuses to have our trans replaced.

I can see it now … “Hey honey, the trans is gonna fail soon. It’ll be about $6500.00 including upgrades. What hotel did you want me to book for Vegas? The shop said something about all you can eat and drink 24/7 and they may comp a room”.

Any spouse heard nothing about $6500 transmission repair, just 24/7 all you can eat and comp’d room

 

[NickTransmissions]

Thanks Nick. If everyone knew you were in Vegas then we’d all be planning honeymoons, week long getaways and excuses to have our trans replaced.

I can see it now … “Hey honey, the trans is gonna fail soon. It’ll be about $6500.00 including upgrades. What hotel did you want me to book for Vegas? The shop said something about all you can eat and drink 24/7 and they may comp a room”.

Any spouse heard nothing about $6500 transmission repair, just 24/7 all you can eat and comp’d room

Basically everybody wins! Not a bad idea at all, haha!

 

[petethepug]

Let some kid loose on it who’s in a computer software class. They’ll set up your web page and a “tentative” itinerary so they can see examples of where they can stay/play based on when you have time for their vehicle.

 

[denalilex]

Hi All,

Since so many of us own at least one Tahoe or Yukon equipped with a 6L80, I figured I'd start an all-encompassing transmission thread with videos, links and other information as it relates to the 6L80/90 transmissions. I'll get it going with a tear down and inspection video and go from there. Hoping this can be an easy 'one-stop shop' for exchanging information, guidance and advice as it relates to 6L80 or 6L90 transmissions.

I'll update this first post with more over time and bump the thread when new stuff gets incorporated.

Feel free to post questions, comments, etc...

Note - Feel free to send me a PM as well but please provide your first name so that I know who I'm talking to - TIA.

2011 6L80 Teardown and Inspection

Special Tools Needed to Work on the 6L Transmissions

6L Transmission - Diagnosis and Troubleshooting, PT1 - Operating Fundamentals and Using Range Charts

View attachment 406082
Quick primer on TEHCM resistance testing:
> Review this article for the TEHCM testing procedures.

> Using a multimeter to test resistance for shift and pressure control solenoids (shift solenoids: 20-40 ohms; line pressure/clutch pressure control solenoids: 3-8 ohms).

clutch pressure control solenoid
View attachment 400908

shift solenoid
View attachment 400907

Pressure switch resistance (closed circuit): .7-1.9 ohms ( this is pressure switch #1 which sends a signal to the TCM reporting the status of the 3-5-R clutch reg valve in the valve body)
View attachment 400909

Pressure switch resistance (open circuit, pressure applied to switch) 11.5-12.9 kohms
View attachment 400910
> Use pencil eraser to put pressure on switch to open circuit
> Pressure switch resistance should drop back to .7-1.9 ohms or so when circuit is closed again (may vary a bit but should not be significantly different).

If any of those pressure switches are not reading like the above when you do this test, then the TEHCM is bad and should be replaced!

TSBs and other Tech Info
ATSG Manual
TSB - Cooler Bypass Valve
TSB - Pump and 3-5-Reverse Drum
ATRA - Intro to the 6L80
ATRA - Changes Over the Years
ATRA - TEHCM Diag, T&E
Installation procedures & fluid level check
GEARS Mag: Diagnosing CAN communication issues (no scan tool)
6L80/90 TSB - UU0073 Communication Breakdown Between Modules (including the TEHCM)


Parts List for Overhaul

PART	GM Part #	Notes
Paper and rubber kit		BW high energy or Raybestos Stage One unless full race
Clutch module
Kolene steel module for 3-5-R and 4-5-6 clutch packs
Factory steel module for 1-2-3-4, 2-6 and low reverse clutch packs
Bonded steel and rubber piston kit		OEM pistons are made by National Seal
Snap ring kit for the 3-5-R and 4-5-6 clutch pack return spring assemblies	24260139	Early spring kit listed will service all years
Snap ring for the rear sprag assembly-to-center support	24230752	Will retro to 2006-E2007 units
Snap ring for the 4-5-6 hub damper cover plate
38 element sprag clutch assembly	24248957	Will retro to 2006-E2007 units
GM heavy duty parking rod assembly (2017 and older)	24280048	12.5" for 6L80E and 14.5" for 6L90E
Factory bushing kit
Thrust bearing kit (only needed if trans overheated)
Sonnax billet aluminum 1-2-3-4 apply piston
Sonnax 4-5-6 piston kit		Optional but strongly recommended
Sonnax Zip Kit		Transgo Reprogramming kit is a viable alternative
Sonnax Oversized Clutch Boost Valve kit		Necessary if one or more existing clutch boost valves fail vacuum test or prove to be worn; requires Sonnax reamer and related tooling for installation
GM internal mode switch	24246427	Updated switch will retro to years 2006-E2007
GM wiring harness and speed sensor assembly		2012+: Application dependent and must match existing rear speed sensor design - consult dealer w/VIN
GM separator plate		Year/application specific - consult dealer w/VIN
GM TEHCM		Optional for later model units and strongly recommended for pre 2014 units; year/application-specific - consult dealer w/VIN
Sonnax pressure switch rebuild kit and tool		Purchase if intending to re-use TEHCM
GM TEHCM filter screen		Purchase if intending to re-use TEHCM
New Torque Converter		New converter should come w/ converter clutch thickness => .050"; billet cover required for heavy duty or high performance
Machine Work
Pump		Machine pump cover and body. Cut pocket to achieve .002 clearance between rotor/slide and deck surface
3-5-R Drum		Reinforce welds at the base of the drum (all years)
High Performance Options
Rear planetary carrier assembly with billet drive plate		Not needed unless horsepower exceeds 700HP or if vehicle is regularly raced
Sonnax 3-5-R high capacity apply ring		When installed and factory wave plate eliminated, this apply ring allows for an additional clutch and flat steel plate
Sonnax 4-5-6 billet clutch hub
Camaro ZL1 Converter		Great performance upgrade as these are significantly stronger than the stock JMBX converters that come w/the 6L80E
Raybestos Blue Plate Stage 3 friction module
Complete Raybestos Kolene steel module

good lord you are just the bomb . com

i’m late to this party - i wound up buried in my 6L80 casket for some time

i’m not trying to toot my own horn or nothing - mainly because i blew it out months ago but - we could go head to head on some intensely heated 6L80 jeopardy/trivia/wheel of fortune these days. jsyk

 

[NickTransmissions]

good lord you are just the bomb . com

i’m late to this party - i wound up buried in my 6L80 casket for some time

i’m not trying to toot my own horn or nothing - mainly because i blew it out months ago but - we could go head to head on some intensely heated 6L80 jeopardy/trivia/wheel of fortune these days. jsyk

I'll take shitttty converter designs for 100, Alex!