GM 6L80 Transmission Information Thread

[Geotrash]

New Question for Nick or Robert (transgo)
I am thinking of relocating my trans external fan forced cooler (for a couple of
reasons). I see that ICT billet has a nice adapter that mounts to my 6l80e
and I can just use only AN lines - my preference.
They make it in a 6an and 8an..
My question is there any advantage or disadvantage to go with the larger 8an
lines from trans to radiator to ext cooler then back to trans ??????
IDK if that changes pressures that would affect anything.. I would think the larger line
would flow a little bit more volume is why I ask.
Right now I'm running the factory steel lines in and out of trans case... with #6 lines
between radiator & ext cooler.
My mods are in signature

I don't know the answer off-hand, but you should be able to easily calculate that based on the ID of the smallest points in the system. The only thing the larger lines would potentially do is 1/ reduce the frictional losses within the hoses, but that's only a tiny fraction compared to any choke points in the fittings and ports on either end of each line, and 2/ give you larger and less restrictive fittings on the hose ends. But if the ID of the fittings at the radiator, at the external cooler, or at the transmission, are smaller than the larger AN hoses and fittings, the larger size AN won't really matter.

 

[Foggy]

I don't know the answer off-hand, but you should be able to easily calculate that based on the ID of the smallest points in the system. The only thing the larger lines would potentially do is 1/ reduce the frictional losses within the hoses, but that's only a tiny fraction compared to any choke points in the fittings and ports on either end of each line, and 2/ give you larger and less restrictive fittings on the hose ends. But if the ID of the fittings at the radiator, at the external cooler, or at the transmission, are smaller than the larger AN hoses and fittings, the larger size AN won't really matter.

I was kinda thinking the same thing... I've done several fuel system projects and
that's kinda the case - except you can just crank up the pressure at the pump and/or
regulate it with external regulator.. So bigger is better IF you need "flow"
Always appreciate your feedback !!!

Anyone else want to chime in ???

 

[CTX-SLPR]

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.

Does anyone one else have HPTuners 6L80 mods and a pressure gauge to check what kind of behavior they are seeing? I’m leaning towards just putting the ZIP kit in and driving it to see what happens. Worst case I have to pull the whole trans out and I’m just out whatever trans fluid I spill around the clean catch basin (fluid has less than 1500mi on it) assuming I don’t find any new bits in the pan.

 

[NickTransmissions]

Bumping this thread with my latest 6L80 video series, this one a high performance build featuring a Circle D Transmissions Level 2 kit and Sonnax billet 4-5-6 hub/intermediate shaft.

 

[Smolski]

Nick,
thanks to your videos I was able to rebuild the gearbox. The gearbox was already rebuilt and someone put it together wrong, i.e. the freewheel was wrongly inserted.

For rebuilding I used Raybestos stage 1 friction and steel clutch kit and sonnax zipkit.
The converter was remanufactured that a reinforced Kevlar disc, only such a possibility I found in my country.

and now 3 questions to which I can not find answers:
1. there are 2 vent hoses attached to the bolt that connects the transmission to the engine, the first one is from the transmission and transfer case unfortunately I do not remember what the second hose is from. I would ask for a hint where to connect it
2.After the rebuild I should do a fast learning of the gearbox but I don't have this option in the scanner. I am using vxdiag nano and tech2win. Do I have to perform this learning? if so is there another way to perform it?
3.At about 35 mph the transmission goes into a strange vibration that only occurs around this speed and has to do with shifting. I suspect that at this speed the transmission engages 2 gears at once. Could this be a problem that the transmission has not yet learned to work properly after the rebuild or maybe I have put something wrong?

 

[Tahoe14]

@NickTransmissions

 

[NickTransmissions]

Nick,
thanks to your videos I was able to rebuild the gearbox. The gearbox was already rebuilt and someone put it together wrong, i.e. the freewheel was wrongly inserted.

For rebuilding I used Raybestos stage 1 friction and steel clutch kit and sonnax zipkit.
The converter was remanufactured that a reinforced Kevlar disc, only such a possibility I found in my country.

and now 3 questions to which I can not find answers:
1. there are 2 vent hoses attached to the bolt that connects the transmission to the engine, the first one is from the transmission and transfer case unfortunately I do not remember what the second hose is from. I would ask for a hint where to connect it
2.After the rebuild I should do a fast learning of the gearbox but I don't have this option in the scanner. I am using vxdiag nano and tech2win. Do I have to perform this learning? if so is there another way to perform it?
3.At about 35 mph the transmission goes into a strange vibration that only occurs around this speed and has to do with shifting. I suspect that at this speed the transmission engages 2 gears at once. Could this be a problem that the transmission has not yet learned to work properly after the rebuild or maybe I have put something wrong?

You're welcome, Smolski. What is a 'freewheel'? Are you referring to the rear sprag or something else?

The Stage One kit is a good kit and Zip kit is my 'go-to' for those transmissions so good on the parts selection. Yes, you need to complete a fast-relearn if you reused your TEHCM...You would need to program the TEHCM if bought new from General Motors or Sonnax. Not sure if Tech2Win works on anything beyond 2013 model years (the hand-held TECH2s do not) but you can purchase a subscription through AC Delco's TDS (Technical Delivery Service) and do your programming or fast adapts via TDS using the correct interface cable with your laptop. Can't speak to the hoses.

What were your clearances in all of the clutch packs (they are shown below)?

Low Reverse
2-6
4-5-6
3-5-R
1-2-3-4

 

[Smolski]

@NickTransmissions
“freewheel" - Low Reverse Sprag Assembly

I used an old TEHCM, the tech2win kit I have connects to it without a problem and I have the ability to read the parameters and test the gearbox. The only option in tech2win that I have is “Reset transmission adepts”.
I did not write down the clutch kit clearances values but they were within the values listed below. These came from the ASTG 6l80 book according to which I assembled the transmission.
Clutch kit clearances:
low/reverse - .050”
2-6 - .050”
4-5-6 - .050” - .074”
3-5-R - .048” - .070”
1-2-3-4 - .060” - .078”

 

[NickTransmissions]

@NickTransmissions
“freewheel" - Low Reverse Sprag Assembly

I used an old TEHCM, the tech2win kit I have connects to it without a problem and I have the ability to read the parameters and test the gearbox. The only option in tech2win that I have is “Reset transmission adepts”.
I did not write down the clutch kit clearances values but they were within the values listed below. These came from the ASTG 6l80 book according to which I assembled the transmission.
Clutch kit clearances:
low/reverse - .050”
2-6 - .050”
4-5-6 - .050” - .074”
3-5-R - .048” - .070”
1-2-3-4 - .060” - .078”

Always keep track of clearances, end play measurements and anything similar as it's a record for what exactly you did to aid in trouble shooting...Mentioning this for anyone else reading that may or may not be aware of how important that sort of data tracking is when it comes to rebuilding transmissions, engines and anything else like-kind. Your third symptom sounds like an overly tight 4-5-6 clutch to me but it could be any number of things, including the TEHCM simply trying to adapt to what it's seeing...Hence why doing the fast adapt helps normalize the control logic and makes getting the transmission back to normal function much faster vs having the TEHCM do it on its own.

Reset Transmission Adapts is the function option you want to select to do the relearn...Click the 'Installation Instructions' link on the first page/post of this thread for step by step instructions on doing the relearn, if you need them.

 

[CTX-SLPR]

Emailed Sonnax about the use of just the valve body side of the ZIP Kit; the answer is yes as the rest of the parts are intended to compensate for wear in the pump which I don't seem to have after watching the pressures.

Dropped the TECHM + VB complex today and tore it down to inspect all of the spools, retainers, etc. What I found was all great except in one area... I have a late 2nd pattern separator plate but the rebuilder had left out the 8th check ball which is directly against the Sonnax instructions.

I don't know what this circuit does but could be the root of some of the wierdness I've been having.

I kept going with the kit and just need to get an inch-pound torque wrench and some DEX VI tomorrow. I debated reusing the 3mth old stuff which I caught in a clean container but now is not the time to cheap out.

 

[CTX-SLPR]

From Sonnax:

That ball being missing very well could have played a factor in your symptoms. It is in the 1st gear circuit and was added to fix downshift complaints and engagement issues.

Those are pretty much my exact complaints so that's a good sign that I'm on the right track.

 

[CTX-SLPR]

So far so good, other than a brief scare when I hit the Trans Fast Learn button in HPTuners and I lost all gears things seem really good. I restored operation by just reflashing the TCU with the tune and the test drive was totally normal. Only thing I noticed was it felt a little soft going into top gear accelerating away from a light a moderate throttle but I don’t really remember how that was before.

Tomorrow I’ll go for a much longer drive to get the temp up to at least the 180’s and see if the 1st gear “overrun” on decel or delayed engagement pulling away come back.

 

[Doug118]

@NickTransmissions my 2008 6l80e operates perfectly when the trans temp is under 150°. The second temps on the gauge go over 150, I lose reverse, and 3rd and 5th gear slips like the truck is in neutral. As soon as they drop back below 150°, everything returns back to shifting smooth and all gears work. Is there something in the tcm that controls line pressure in those gears or something else electrical that could be wrong? It’s very odd that it can go from perfect to losing those gears back to perfectly fine within a 15 minute drive

Also, temps climb pretty rapidly if I sit idling for a few minutes. As soon as I drive, temps start to drop again

 

[NickTransmissions]

@NickTransmissions my 2008 6l80e operates perfectly when the trans temp is under 150°. The second temps on the gauge go over 150, I lose reverse, and 3rd and 5th gear slips like the truck is in neutral. As soon as they drop back below 150°, everything returns back to shifting smooth and all gears work. Is there something in the tcm that controls line pressure in those gears or something else electrical that could be wrong? It’s very odd that it can go from perfect to losing those gears back to perfectly fine within a 15 minute drive

Also, temps climb pretty rapidly if I sit idling for a few minutes. As soon as I drive, temps start to drop again

Could be one or more of (but not limited to) the following:

1). TEHCM - trans temp sensor failing; line pressure control on the fritz (not likely)

2). Torque converter - failure is their middle name (probable)

3. Burnt 3-5-R clutch pack due to drum leaking at the base welds (my chief suspect here)

Trans will need to come out for overhaul, is my thinking...Scan the pcm for codes, particuarly gear ratio error and/or solenoid performance codes...those are dead giveaways of a smoked 3-5-R pack...

 

[Tahoe_Denali]

Nick, my question is on trans operating temperature for a 07 Yukon Denali.

Background: My truck had the transmission replaced @165k with a GM reman. @295k the reman was rebuilt by a reputable local shop. New GM Techm, upgrade TC, and other known failure upgrades sonnex etc. @305k summer is near with ambient temperature rising so I have started watching the trans temp.

Truck drives fine, but trans operating temperature has the engineer in me scratching my head. I drive the same route in the AM when it is 50 degrees outside and trans temp is in the 153-160 range, but as it hit 90 yesterday afternoon the trans temp went as high as 197, not towing.

Trans shop is telling me this is normal for a truck that pulls hills. I have read a lot of conflicting things, some would agree others say over 180 there is something wrong.

What is your take?

 

[donjetman]

@Tahoe_Denali
totally normal
My still going strong 200k mile 07 Denali w/6L80 has the factory installed medium duty (rpo KNP) trans cooler setup and always runs 80-100* over ambient. If its 110* outside tranny runs 190-210*. This is normal and Dexron6 can handle it and a whole lot more. I installed a newly rebuilt torque converter 6+ yrs ago at 130k miles.

When I have any question(s) about atf I call Tom Johnson at JG Lubricant Services ph 877-971-7799, ext#2. He's a retired GM/Allison fluids engineer. I also use their services for allmy used atf analysis.
https://jglubricantservices.com/

 

[NickTransmissions]

Nick, my question is on trans operating temperature for a 07 Yukon Denali.

Background: My truck had the transmission replaced @165k with a GM reman. @295k the reman was rebuilt by a reputable local shop. New GM Techm, upgrade TC, and other known failure upgrades sonnex etc. @305k summer is near with ambient temperature rising so I have started watching the trans temp.

Truck drives fine, but trans operating temperature has the engineer in me scratching my head. I drive the same route in the AM when it is 50 degrees outside and trans temp is in the 153-160 range, but as it hit 90 yesterday afternoon the trans temp went as high as 197, not towing.

Trans shop is telling me this is normal for a truck that pulls hills. I have read a lot of conflicting things, some would agree others say over 180 there is something wrong.

What is your take?

Anything under 220 for these units is generally ok as Dex6 was engineered to withstand higher temp operating regimes. My GMC Sierra's 6L80 typically runs between 140-160 when cruising around normal driving, no towing/no heavy weight hauling. It will get to around 185-200 in stop-n-go traffic when temps are 80+. As long as the unit doesn't start to present with symptoms when temps get on the hot side, and the hot side is not any more than 220 and only for short periods of time, you should be fine.

If you have a vehicle equipped with three or four-speed unit running conventional Dex/Merc, I would recommend keeping temps at 185 or less at all times...

 

[Tahoe_Denali]

Anything under 220 for these units is generally ok as Dex6 was engineered to withstand higher temp operating regimes. My GMC Sierra's 6L80 typically runs between 140-160 when cruising around normal driving, no towing/no heavy weight hauling. It will get to around 185-200 in stop-n-go traffic when temps are 80+. As long as the unit doesn't start to present with symptoms when temps get on the hot side, and the hot side is not any more than 220 and only for short periods of time, you should be fine.

If you have a vehicle equipped with three or four-speed unit running conventional Dex/Merc, I would recommend keeping temps at 185 or less at all times...

Thanks, I guess the true test will come when I hook the boat up and head to Tahoe for memorial day. Will update as Summer heats up.

 

[donjetman]

Thanks, I guess the true test will come when I hook the boat up and head to Tahoe for memorial day. Will update as Summer heats up.

yeah, I wouldn't do any towing with my 6L80 unless I installed a large aftermarket cooler with fan(s) setup like others have done here, like IIRC @Geotrash, etc.

 

[Chrispi]

You're welcome, man...

Nope, was referring to the valve body assembly in the ZF5HP19 - has literally 20 or 25 little restrictors that lie in their respective locations in the channel plate and will stick to the separator plate if you take it off without knowing to use a pick to unseat them so you know where they go. Each restrictor has a small orifice in the center and there's a bunch of different size orifices and would be damn near impossible to know where they went if you didn't keep track (unless you build those units every day).

Here's a few shots of the vb
View attachment 400834

Restrictors are at bottom right
View attachment 400835

Spacer plate lifted off channel plate to show all hydraulic circuit orifice restrictors
View attachment 400836

Hello. I have issues with slight increase rpm (100-500) during decelerating/braking. i ruled out brake booster as this did not fix the issues. was wondering it could be transmission issues? it does this at hot weather.