Transmission fluid leak?

kpanza · May 30, 2020

26 minutes ago, Shiva said:

Curious... What is the build date of your truck? My Denali 6.2 is 2/20. From Mexico.

Got got mine back they did the dye in the engine oil washed off the engine bay and drive for 6 miles. Couldn't find any oil leak. The mgr took it home last night to test and let the oil work through. No oil leak detected. The oil at the dip stick has been full from day one.

I'm hoping it was just some Yahoo in Mexico who couldn't aim the oil hose right and spilled it in the engine bay.

I guess I will just keep an eyes on it and check with my own black light at home.

Mine was 2/04/20 build, Mexico. 6.2L/10 spd. Still at dealer awaiting a pump, or a whole tranny, or whatever the hell they come up with next. I picked a replacement truck from their inventory last weekend, was told that the truck was "off the floor", was mine for the GM Replacement...later that day I get a call that the sales manager sold it from under me. Might just get my money back and tell them all to pound it.

Jonathan Bowman · May 31, 2020

I have a new 2020 Sierra SLT with the Duramax, tranny fluid everywhere. 300 miles. Wtf is going on.

Jonathan Bowman · May 31, 2020

On 3/18/2020 at 11:49 AM, kpanza said:

No one else had this issue? Truck is at the stealership now, I will post up what they find. Service advisor seemed pretty used to this complaint, said they even have an aftermarket silicone sealant that works better than the factory stuff on the plastic pans...we will see.

Yes, just saw the tranny fluid everywhere. 2020 SLT with the baby duramax

Colossus · May 31, 2020

3 hours ago, Jonathan Bowman said:

I have a new 2020 Sierra SLT with the Duramax, tranny fluid everywhere. 300 miles. Wtf is going on.

loose tranny cooler line. It happens sometimes. Even on new vehicles.

kpanza · May 31, 2020

Not the cooler lines, at least not on mine. Starting to think this 10spd has issues...go on the Ford forums and there's all kinds of complaints like this. Mine wasn't even the pan leaking, is something internal. If they ever actually fix it, I'll let you know what they come up with this time.

Shiva · May 31, 2020

I haven't seen any issues with my tranny yet. I had a 2018 F-150 before traded for my Denali last week. Never had an issue with the 10 speed. The reason why I traded was the cam phaser issue with the 3.5 ecoboost. Dealer refused to even acknowledge it. Could be just really bad QC. Too many vendors providing diff components.

Got my Denali in the garage with cardboard under the engine. My blacklight will be here tomorrow so I can look for engine oil leak.

DFW-AT4 · June 1, 2020

Count me as another with a transmission issue. 2020 AT4 with 3.0L Duramax. Just got back from a fishing tournament today only to find my boat coated in transmission fluid. Looked under the truck and it was gushing out from the back of the motor. I've ONLY had it for 3 weeks and has less than 900 miles!

steve841 · June 1, 2020

Uh oh ..... Please let us know what service finds/does to repair.

kpanza · June 3, 2020

So, after 65 days out of service, the dealer called and says the transmission is fixed. Going to pick it up tomorrow and find out. I am going to drive it a few weeks and see if all is good, then decide what to have GM do. I'll either get it replaced (was approved for buyback/replacement last month), or get GM to compensate me for my 4 payments already made. Not much inventory to pick from on the replacement end, so we will see. I really just want to drive the damn thing and enjoy it. Fingers crossed.

I'll let you know what the actual service receipt says was replaced, as the service writer has no clue. All I know is it is NOT a brand new transmission, as there aren't any available at the moment.

kpanza · June 5, 2020

Well, I have truck back. They replaced the front case cover, front seal and torque converter. They drove it about 25 miles and so far no leaks. Fingers crossed that this 66 day saga is over and I can just enjoy the truck. Hopefully this is not a widespread problem for others. They did at least follow my request, and they did a full detail on the truck, plus filled it with gas. They really want their completely satisfied review!

Edited June 5, 2020 by kpanza

Stephen Foster · December 28, 2020

Found this leak on my duramax pretty interesting the manufacturer let this roll, then to boot while fixing this i fould a engine oil leak at the oil filter adapter. My truck has 1400 miles on it.

Oscar Winner · February 6, 2023

I picked up this 2.7 2020 GMC in mid-December. Notice that it has several oil spots under it every morning. I have about 35k on it. Shifts badly when decelerating around 20-15 mph. Spots seem to be under the transmission rather than the engine. Is this what I'm in for with this truck?

mx_599 · July 5, 2023

I have a GM 8L90 transmission with less than 1000 miles leaking fluid which sounds similar to the above.

Were the other people in this thread 8L90 as well?

due to life circumstances, my vehicle has been stored and I think out of warranty now so I might be stuck with this myslef

What has been the fix or problem with new GM 8L90 's and the leaks? what is the fix?

thanks

Bikerjon · July 7, 2023

What year is your truck?

Larry Driver · September 17, 2023

2016 silverado 1500 8speed trans , took it to dealer , mechanic said was trans pan gasket and replaced it on Thursday , on friday drove 200 miles saturday noticed trans. fluid leak on garage floor size 8" puddle , call made appointment at dealer 14 days later , mechanic said new leak , trans. shifter linkage was bad , charged again $$. Anyone with problem. Trans. pan gasket was not the problem ( OPINION )