CTX-SLPR
Member
From Sonnax:
Those are pretty much my exact complaints so that's a good sign that I'm on the right track.
GM 6L80 Transmission Information Thread
- Thread starter NickTransmissions
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CTX-SLPR
Member
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.
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
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@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
Also, temps climb pretty rapidly if I sit idling for a few minutes. As soon as I drive, temps start to drop again
OP
OP
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
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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?
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
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@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/
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/
OP
OP
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
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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.
