2015 Truck 6.2 L Engine, 8L90E Transmission troubles, problems, fixes

20L8TSierra24 · August 28, 2015

Got my Recalls done today, it is definitely better.

Recall 15178/15389

Sent from Off Driller Side

Glad to hear

Jtodd · February 13, 2016

Just purchased a 2015 Gmc 1500 Sierra 6.2 8 speed ..just after 2nd week of owning it, I started to experience hard shifting when I accelerate and decelerate. Took to dealership 1st time was told it was learning my driving habits...would get better after a while..it never got any better...just has its days when it fine and then acting up...I keep taking truck back because I am so tired of all the shifting problems, some times it shifts hard enough that it feels like tranny is going to fall out, have taken it back 2 times since. Dealership conntaced Gmc techs to solve problem...they have done two software updates...but nothing helps. I have a case with Gmc they tell me to take it to a nother local Gmc dealer to see if they can fix the problem...this has been a crazy experience...I don't even want the truck anymore! I have spoken to random people I see at gas stations or parking lots with the similar transmission and they are experiencing the same problems...dealership has told me they have not had any other complaints but I know they're not telling the truth. I'm going to pursue the lemon law, if this next dealership can't fix it....Paid 55k for nothing but problems!

Jerry's Denali · February 14, 2016

Been thru 4 months of the same song and dance, wasted a lot of my time.

Last week I removed my trans and disassembled it and found several surprises.

Parts are unobtainable so I'm getting a new trans on my dime(for now).

Its been 30 years since I disassembled a GM trans, back when the 700R4's came out with all of its problems.

Will update later when I get it reinstalled AND confirm I fixed it.

4800 miles on a $59000 truck, and I have to fix it.

Rock1500 · February 15, 2016

Been thru 4 months of the same song and dance, wasted a lot of my time.

Last week I removed my trans and disassembled it and found several surprises.

Parts are unobtainable so I'm getting a new trans on my dime(for now).

Its been 30 years since I disassembled a GM trans, back when the 700R4's came out with all of its problems.

Will update later when I get it reinstalled AND confirm I fixed it.

4800 miles on a $59000 truck, and I have to fix it.

What were the surprises? Sorry to hear you have to do all the work.

It's thing like this that hold me off from trading my 2014 5.3 truck for a newer model. The truck has given me non issue and has been great. Why jinx it.

Sent from my SM-N900V using Tapatalk

Jerry's Denali · February 15, 2016

Lots of clutch material in pan, valve body bolts not torqued to spec, 1 was loose and laying in pan.

I cannot say (yet) that it is 100% fixed, but the delayed engagement from park to drive is gone!

It shifts fine and so far no clunking. I did follow the learning procedure to the letter. That took about 80 miles all total.( I also did this for the old trans with no change)

The clunking, harsh downshifts I was experiencing was somewhat infrequent (about every other day of in town driving), so I will have to drive it more to really claim it's fixed.

The trans,torque converter and fluid was $2900 with a $1500 core that I paid so I could keep my trans for evidence.

If its 100% fixed GM will pay me for my trouble, this I assure you.

4 different GMC dealers told me my issues were normal, yet thousands are complaining and the trans is very difficult to get from GM parts.

Mine came from a third party who is working on a solution for the all of the GM 8 speeds focusing on the Corvette mainly.

Jtodd · February 17, 2016

Been thru 4 months of the same song and dance, wasted a lot of my time.

Last week I removed my trans and disassembled it and found several surprises.

Parts are unobtainable so I'm getting a new trans on my dime(for now).

Its been 30 years since I disassembled a GM trans, back when the 700R4's came out with all of its problems.

Will update later when I get it reinstalled AND confirm I fixed it.

4800 miles on a $59000 truck, and I have to fix it.

Lots of clutch material in pan, valve body bolts not torqued to spec, 1 was loose and laying in pan.

I cannot say (yet) that it is 100% fixed, but the delayed engagement from park to drive is gone!

It shifts fine and so far no clunking. I did follow the learning procedure to the letter. That took about 80 miles all total.( I also did this for the old trans with no change)

The clunking, harsh downshifts I was experiencing was somewhat infrequent (about every other day of in town driving), so I will have to drive it more to really claim it's fixed.

The trans,torque converter and fluid was $2900 with a $1500 core that I paid so I could keep my trans for evidence.

If its 100% fixed GM will pay me for my trouble, this I assure you.

4 different GMC dealers told me my issues were normal, yet thousands are complaining and the trans is very difficult to get from GM parts.

Mine came from a third party who is working on a solution for the all of the GM 8 speeds focusing on the Corvette mainly.

Jtodd · February 17, 2016

Just made a appointment with a new dealership in my area...Gmc asked me to give a different dealership a chance to fix my transmission troubles...this will be the 4th time I take it in..In three months for same hard shift issues...they said if they don't fix it they will get me out of the truck..but they weren't able to tell me what that intititles.

Jerry's Denali · February 17, 2016

I am convinced mine is fixed now. After over 450 miles not one single hiccup.

Delay from park to drive is completely gone also.

GM will have to fix my other Denali or buy it back, I'm not going through this again.

Jtodd · February 17, 2016

I am convinced mine is fixed now. After over 450 miles not one single hiccup.

Delay from park to drive is completely gone also.

GM will have to fix my other Denali or buy it back, I'm not going through this again.

Jtodd · February 17, 2016

Your Denali has similar transmission issues?And have you had it in for service?

intimidator01238 · February 18, 2016

I am convinced mine is fixed now. After over 450 miles not one single hiccup.

Delay from park to drive is completely gone also.

GM will have to fix my other Denali or buy it back, I'm not going through this again.

What all did you end up having to fix? Do you have more details? I know you had mentioned there was bolts not torqued to spec and clutch material but was there more?

Jerry's Denali · February 18, 2016

I replaced the transmission and torque converter.

The parts I needed to fix mine are unobtainable right now.

I reassembled it and now gonna battle GM for reimbursement and after speaking with my attorney today, I should get my money back.

Jerry's Denali · February 18, 2016

Your Denali has similar transmission issues?And have you had it in for service?

I have 2 2015 Sierra Denalis, one was not too terribly bad but the other clunked and shuddered so bad my Wife refused to ride in it. That is the one that is still screwed up. We left it at our beach house in Destin. After numerous visits to 4 different dealers I refused to drive it another mile. I have a wrecker delivering it to the dealer Friday morning. It has less than 1000 miles on it.

Mine that I drive every day is fixed now.

Jtodd · February 18, 2016

I have 2 2015 Sierra Denalis, one was not too terribly bad but the other clunked and shuddered so bad my Wife refused to ride in it. That is the one that is still screwed up. We left it at our beach house in Destin. After numerous visits to 4 different dealers I refused to drive it another mile. I have a wrecker delivering it to the dealer Friday morning. It has less than 1000 miles on it.

Mine that I drive every day is fixed now.