GM 6L80 Transmission Information Thread

NickTransmissions · Oct 30, 2024

Smolski said:
Hello,
Unfortunately my 6l80 gearbox needs repair, it jerks and the gears slip. I tried to find a competent mechanic who will rebuild it, but since cars with this gearbox are not offered in Europe, mechanics really appreciate the repair of this gearbox. I decided to repair it myself, I have the skills to do it properly. I would only ask for help in selecting the parts I need to use so that the gearbox works well for the next 3-4 years. I have a modest budget for this operation, but I hope that it will be possible to do it for 2500 dollars. In this amount I have to fit everything, i.e. the regeneration of the converter ~300 dollars, and the remaining parts along with shipping and taxes. I am considering buying the
circle D stage 2 kit https://www.circledtrans.com/6l80-level-2-performance-kit
or
RAYBESTOS stage 1 deluxe rebuild kit in pis https://www.ebay.pl/itm/176644936969?_skw=6L80+Performance+Transmission+Rebuild+Kit&itmmeta=01JB3HM8F4HJW834CDG3RNEBKQ&hash=item2920dbd509:g:A8MAAOSwmPJmAmOn&itmprp=enc:AQAJA

You can advise whether any of these kits contain everything I might need for the rebuild? of course I am aware that I may have damaged elements that are not always subject to replacement. I also know that parts should be ordered after disassembly and inspection of the parts, but I cannot afford to block the car for so long.
I hope you will understand and try to help with choosing what to do.

Best regards

$2500 US is doable if you don't have to replace your TEHCM.

I just ordered the Lvl2 kit from Circle D for a performance-oriented build that I'll be filming for Youtube in a couple weeks...I may or may not augment that kit with the Raybestos stage one friction set for the 4-5-6 as the Circle D kit comes with Borg Warner frictions (nothing wrong with those clutches) but the Stage Ones are a little more resilient to heat which is a big problem with that 4-5-6 clutch.

The CircleD kit comes with everything you'll need except for the electronics (TEHCM, IMS, Harness-speed sensors) and a few choice hard parts like the Sonnax billet 1-2-3-4 piston. I'd also purchase the Transgo clutch select valve and spring kit as well to augment what Circle D provides. If you're pushing over 500HP, I'd grab the Sonnax 4-5-6 billet hub/shaft assembly as well.

Hope that helps.

Smolski · Oct 30, 2024

Thank you for your reply, I will decide on the circle D if the shipping costs are not too high.

I do not plan to increase the power in the car, I simply want a working gearbox. Can you tell me more precisely which TransGo kit you would buy?

Also, can you explain to me what the converter upgrade by installing a thicker clutch disc involves? I will ask a local contractor about such a service, but I do not fully understand what it is about.

NickTransmissions · Oct 30, 2024

Smolski said:
Thank you for your reply, I will decide on the circle D if the shipping costs are not too high.

I do not plan to increase the power in the car, I simply want a working gearbox. Can you tell me more precisely which TransGo kit you would buy?

Also, can you explain to me what the converter upgrade by installing a thicker clutch disc involves? I will ask a local contractor about such a service, but I do not fully understand what it is about.

Go to Transgo's website, click on 6L80 and you'll see all of the kits and parts offered for those transmissions...One of them is the clutch select valve kit...

Torque converter: Install a .070 thick Borg Warner HE converter clutch...You can also have the TC builder do a flanged hub for addl strength though it's not needed in a daily driver/stock application. Same with a billet converter cover - high performance only.

CTX-SLPR · Nov 6, 2024

Nick,

How required are the pump mods in the Sonnax and Transgo kits?
I think I’m having problem related to the TECHM hydraulic side of things so pulling that part in the vehicle is a no brainer to replace the check balls, valves, and springs but the pump mods would require dropping and disassembling things which is a much bigger investment up front while trying to narrow it down.

Thanks

NickTransmissions · Nov 6, 2024

CTX-SLPR said:
Nick,

How required are the pump mods in the Sonnax and Transgo kits?
I think I’m having problem related to the TECHM hydraulic side of things so pulling that part in the vehicle is a no brainer to replace the check balls, valves, and springs but the pump mods would require dropping and disassembling things which is a much bigger investment up front while trying to narrow it down.

Thanks

I dont ever rebuild one of those transmissions without one of those two kits or an equivalent. Take that for what it's worth to you.

If you think the TEHCM is problematic either bench test it using a DVOM, 12-volt power supply and the Bosch 6L TEHCM test block. If you dont have the test block kit, you'll need to get it to a shop that has one.

Otherwise you're not going to be completely sure if everything passes the DVOM and 12-volt p/s tests...

CTX-SLPR · Nov 7, 2024

NickTransmissions said:
I dont ever rebuild one of those transmissions without one of those two kits or an equivalent. Take that for what it's worth to you.

If you think the TEHCM is problematic either bench test it using a DVOM, 12-volt power supply and the Bosch 6L TEHCM test block. If you dont have the test block kit, you'll need to get it to a shop that has one.

Otherwise you're not going to be completely sure if everything passes the DVOM and 12-volt p/s tests...

Nick,

I think it's the hydraulic part that's the problem, i.e. valves or checkballs are sticking when it gets heat soaked as it's only evident after 45+ min of driving when you come to a stop or get moving from one. To me that seems like the first step is to pull the full unit and put the Sonnax ZIP kit in it minus the pump pressure regulator mods and see how things go. My concern is that without the pressure regulator mods the rest of the kit won't work properly and I'll just get more problems.

NickTransmissions · Nov 7, 2024

CTX-SLPR said:
Nick,

I think it's the hydraulic part that's the problem, i.e. valves or checkballs are sticking when it gets heat soaked as it's only evident after 45+ min of driving when you come to a stop or get moving from one. To me that seems like the first step is to pull the full unit and put the Sonnax ZIP kit in it minus the pump pressure regulator mods and see how things go. My concern is that without the pressure regulator mods the rest of the kit won't work properly and I'll just get more problems.

First thing I'd do if I were you is a line pressure test...Wear in the PR valve should show up there...Refer to the first page and post of this thread for the ATSG manual which has line pressure testing information...If you find that your line pressures are below normal, simply yank out and overhaul the unit completely.

I will be filming a 6L80 performance build up using one of Circle D's level 2 kits starting next week and will have the video series published to my YT channel towards the end of next week so you can follow along...It will be a complete and total overhaul with all parts and procedures shown.

CTX-SLPR · Monday at 9:16 PM

Drove it for around 30min with the gauge under the wiper, max temp was 189 on the DIC which matched the TECHM sensor value when I had a scan tool on it. Now I have done the HPTuners changes to pressures, slips, and a bit of turning on the 2-1 and 3-1 shift timings so I'm not strictly the same as stock anymore.

Out of gear idle: ~75psi
In gear idle: started at ~75psi but as it got warmer it dropped to 60psi

Driving around it was around 90psi with spikes to 120-160psi during shifts or as high 210psi if I got on it

The gauge seemed very responsive like the TECHM was commanding different pressure for upshifts, downshifts, and lockup and the regulator/controller was responding. I did see a few brief pressure drops on downshifts but things felt normal. I have some videos but it won't let me upload them.

GM 6L80 Transmission Information Thread

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CTX-SLPR

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