GMC Sierra Denali (8L90) 8 speed teardown

This is a disassembly of an 8L90 automatic transmission out of a 2015 GMC Sierra Denali with a tune and a big camshaft . #8l90 #automatictransmission #chevrolet #denali #gmc #mechanic #6l80 #10r80 #automotive

[@colbys2270]

Finally a good video doing a tear down and explaining everything, thanks !

[@esoterictransmissions]

Certain 2016 Escalades equipped with the 8L90 WERE under a special coverage for failure of the internal wiring harness assembly. However, this is issue plagues all units in the 8L family even 8L45s in Colorados and or Camaros.

[@adamhorvat9515]

could you do a video on how to measure clutch clearance on this transmission ?

[@jayeritsland9780]

I just got a 2015 Yukon 6.2 8L90 with 122K, seems like it was taken care of. It has a delay 1-2 shift mostly first shift of the day. I just did a fluid change 12 quarts mobile 1 blue label, drained through the cooler lines running 10 seconds at a time. The pan looked pretty good, but the fluid was pretty dark. I have not really noticed much shudder except maybe at really low RPMs. I also just installed the superior solutions thermostat valve upgrade. I want to take it on some back country trips and maybe Canada, but now a little worried about reliability. I was surprised and happy to hear you did not think there were a lot of 8L90 converter failures. The temp sensor seems to be working fine. Should I just worry less and drive or should I do anything else to it? Great vid BTW, subscribed.

[@esoterictransmissions]

@@jayeritsland9780 Congrats and good job on servicing it man! If I were you I would drive it till there is absolutely a problem. I think you should be safe to keep driving it. However, You’re at the mileage where you will likely have some issue arise. Whether that’s valve body, internal temp sensor, or chain etc so I would budget $5-6k for transmission to be on safe side.

[@paulcondie2520]

I have a 2017 Silverado with the 6 speed, bought it used at 45,000 miles. I did my research before hand and installed the lower temp thermal bypass and full fluid change, will this extend the lifw of my torque converter? My average running temp is 145. I had seen one of your KZbin shorts. Thanks!

[@esoterictransmissions]

@@paulcondie2520 To be totally honest man every single 6L80 equipped truck or SUV from 2014-2019 with the original torque converter will have a failure anywhere from 45-145,000 miles. It’s not IF it’s when but if you catch it in time or replace the converter when it begins to shudder you can save the transmission. To answer your question, yes. The cooler it can run the better. GM actually requires you to replace the thermal valve with an updated part anytime you rebuild a 6L80/90 under warranty. However, most 6L80 equipped 1500 pickups and SUVs are out of warranty by now. I rebuilt a 2019 Tahoe that was barely under certified powertrain months ago. Just budget for it and keep the truck!

[@edwardbarden4722]

I have a 2020 Sierra SLE with the 8L90. Its a certified preowned and apparently at about 50k it had the new fluid (hp) put in and whatever else done per a TSB. Sometimes this thing when its cold has a delay between 1 and 2 taking off for the day. Also when putting in reverse has such a clunk. I read it was the "chevy clunk" but for a newer trans does that still hold true? Whats your thoughts?

[@esoterictransmissions]

@@edwardbarden4722 The harsh 1-2 shift of the day is actually a normal operating characteristic and it is due to trapped air being purged from the 2-4-6-8 and 4-5-6-7-8-R clutch assembly. The clunk in reverse is also likely normal as it can be attributed to lash in the driveline. Try letting your foot off the brake when shifting to reverse and it will be more smooth. You must also remember that it is a truck and it can shift like one sometimes.

[@edwardbarden4722]

@@esoterictransmissions ok, all make sense. Thanks for the response. Otherwise it has been a decent truck... so far. Hopefully the engine holds up. lol

[@HewigIsidore]

On the 8L90 8 speeds, there are no plastic tabs that hold the halves of the valve body together, it’s metal tabs on opposite ends on the inside of the valve body. The separator plate has to fit over the 2 metal tabs inside the valve body and there are just there to line it up upon reassembly. The solutions to fixing the problems with these 8L90 Transmission are 4 things. 1. TRANSGO thermostat cooler bypass delete kit. It drops the transmission temperature by 60-70 degrees. 2. SONNAX Shift Kit. 3. SONNAX TCC Kit. 4. Disable AFM/DOD. This will fix all of the issues concerning this 8 speeds. How do I know this? Simple. I did my 16 Escalade at 22,000 miles. Now, I have 92,000 miles. No issues and the transmission fluid temperature never goes higher than 165F.

[@esoterictransmissions]

@@HewigIsidore I think you’re confusing dowel pins for separator plate retaining clips but yes every issue in them stems from valve body.

[@newbtubetecher]

What dealership are you at? Id have you rebuild mine

[@esoterictransmissions]

I’m at a GM dealer in Maryland. Message me on tik tok if you can