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

Ron.s · March 26, 2016

Use a PM!

jetfixer737 · March 27, 2016

I've read thru many of the threads here on the 8 speed, and mine has the same 1-2 upshift/downshift jerkiness everyone else discusses here. Every time I take it in for routine service (15,000 on the odometer now) I complain. At the original dealer in Boise I was told by their lead transmission mechanic the physical transmission is practically bulletproof (his opinion) but they all admit the computer programming is a mess. The frustrating thing tho is that they admit a major software patch is needed, but GM hasn't/won't provide one. (Some I've spoken to wonder if GM is even bothering to look into it)

However my 8 speed has yet another issue I haven't noticed anyone else mention:

When traveling very slowly (under 5 mph) on occasion I've felt my transmission disengage, almost as if its going into neutral, then after pushing the gas it harshly re-engages. The problem is in 9 months of ownership its only done it a handful of times, so a dealer would probably have to have it for weeks before they could duplicate the problem.

Has anyone else experienced this?

(Now I see the new GM/Ford 10 speed auto is out there in the Ford Raptor and 2017 ZL1 Camaro...heaven help us)

Performancemp2 · March 29, 2016

I purchased a 2015 GMC Sierra November 21st, 2015. At 569 miles it was in the shop. To make a long story short. The dealership has had my vehicle 43 days out of the 140 I have owned it. Been in the shop 8 times now, currently has 6,200 miles. The transmission has been pulled twice. Ist time for a defective torq converter and the 2nd time a new transmission that was backordered from GM. I recently recieved it back friday and its a clunker! I've been given the run around from GM, no returned calls when they stated they would. I was able to capture the truck acting up on video to where it jerked so hard it almost knocked my phone out my hand. After being a loyal GM fan for over 25 years this will be the last.

Link to video, Sorry for my noise, scared the crap out of me.

harveyfamily · March 29, 2016

Have you contacted your district manager for GM? Sounds like it's buyback time.

Performancemp2 · March 29, 2016

Have you contacted your district manager for GM? Sounds like it's buyback time.

Believe me I've tried. I spoke with Ebony on Friday with GM customer service and she was suppose to get back today, no returned call. I've been asking for resolution for the past 2 months asking for GM to buy back the vehicle. All they have offered this far is to pay a note on a 53k dollar truck.This has happened in the past, promised to return my calls with a resolution. Never calls back and ignores messages. Its a shame that GM will not respond or resolve an issue to this magnitude. Its apparent that the only way GM will respond is if u take legal action.

Jtodd · March 31, 2016

Update:

Going on day 3 haven't heard a peep or email from 6 people who are currently working on my case! ( 2 service managers) ( 2 area representatives for GMC) (2 customer care reps) It's crickets over here!!!!!!!

pm26 · March 31, 2016

I purchased a 2015 GMC Sierra November 21st, 2015. At 569 miles it was in the shop. To make a long story short. The dealership has had my vehicle 43 days out of the 140 I have owned it. Been in the shop 8 times now, currently has 6,200 miles. The transmission has been pulled twice. Ist time for a defective torq converter and the 2nd time a new transmission that was backordered from GM. I recently recieved it back friday and its a clunker! I've been given the run around from GM, no returned calls when they stated they would. I was able to capture the truck acting up on video to where it jerked so hard it almost knocked my phone out my hand.

The truck is performing as designed and built.

wetcoaster · March 31, 2016

I've put about 2000km's on my 2015 6.2 8 speed and have noticed weird hard shifts. Is there a TSB someone can point me to?

Docknow9 · April 4, 2016

I purchased a 2015 Sierra SLT w/6.2L 8 speed in August 31. Sticker was $56,910.00. I got $11,600.00 off and $30,000 on trade for my 2012 Acadia Denali with 29,000 miles on it. I feel got a wonderful deal. I currently have 11500 miles on it and have averaged 20 mpg overall. Last trip of 400 mile I get 22.4 mpg. It is the best performing and riding truck I have ever owned.

Jtodd · June 26, 2016

Update!!

2015 GMC Sierra 6.2 liter still not fixed ( 7 times to two different dealerships) (2 brand new transmissions ) ( 1 field technician flew in to fix my truck 30 days in shop and when

I got my truck back with 790 additional miles it still isn't FIXED!!!!Just had a meeting with a dealership representative he wants to continue to try to fix my truck...These people are crazy!!!!!!..They just won't give me my equity back...My arbitration is at the end of July through the BBB...Can't believe they are taking it this far..I would have thought they would have done a buy back by now..Worst car company and the most problems I have ever had with a vehicle.Never will I recommend or purchase a GMC product!

wetcoaster · June 26, 2016

I'm on 3 trips and 2 software updates and no fix in sight. I've been told again to wait a 1000km to see if the magic adaptive settings will clear it up.

Jtodd · June 27, 2016

All I can say is start documenting everything..Call GMC support and make a case with them. Start investigating the BBB auto line. It is like the Lemon Law..But GMC participates in it through the BBB. They push the case within 30 days but you must follow the guide lines..Good Luck!!

pm26 · June 28, 2016

Update!!

2015 GMC Sierra 6.2 liter still not fixed ( 7 times to two different dealerships) (2 brand new transmissions ) ( 1 field technician flew in to fix my truck 30 days in shop and when

I got my truck back with 790 additional miles it still isn't FIXED!!!!Just had a meeting with a dealership representative he wants to continue to try to fix my truck...These people are crazy!!!!!!..They just won't give me my equity back...My arbitration is at the end of July through the BBB...Can't believe they are taking it this far..I would have thought they would have done a buy back by now..Worst car company and the most problems I have ever had with a vehicle.Never will I recommend or purchase a GMC product!

Maybe it is time people started demanding a good manual transmission option in these trucks.

Jtodd · June 29, 2016

I have learned my lesson! I'm staying away from GMC..First and last I ever buy..I test drove a Ford Platinum for a week with the 5.0..VERY NICE!Ford is getting my business

Badass69 · June 29, 2016

I have around 24000 miles on my 8 speed truck and my only complaint I have an issue with is the delay from park which it has done from day one. Well there is a TSB out for it and even my tuned (tweaked by me HP dyno tune set back to a stock tune I had to build as my original got overwritten) truck was fine. I have never been the dealer for service before and never bought a thing from them.... but they tested it and ordered the stator assembly and whatever else the TSB calls for. Once that is done all should be well again!