Jump to content

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

NiceDay

By NiceDay
in Troubleshooting & Recalls

Recommended Posts

  • Replies 76
  • Created
  • Last Reply
jetfixer737 Enthusiast

jetfixer737

Posted
Posted

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 New Member

Performancemp2

Posted
Posted

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.

 

 

Performancemp2 New Member

Performancemp2

Posted
Posted

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 Enthusiast

Jtodd

Posted
Posted

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 Senior Enthusiast

pm26

Posted
Posted

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 Enthusiast

wetcoaster

Posted
Posted

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 Enthusiast

Docknow9

Posted
Posted

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.

  • 2 months later...
Jtodd Enthusiast

Jtodd

Posted
Posted

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 Enthusiast

wetcoaster

Posted
Posted

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 Enthusiast

Jtodd

Posted
Posted

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 Senior Enthusiast

pm26

Posted
Posted

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 Enthusiast

Jtodd

Posted
Posted

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 Senior Enthusiast

Badass69

Posted
Posted

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!

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Latest Articles

  • Posts

    • Chuck FB
      summer road trips in the 2026 2500HD

      By Chuck FB · Posted

      I thought I would use your thread and add to it as I just did my first longer drive with my truck in the last couple of days. I drove from the Grande Prairie area of Alberta down to Edmonton and most of where I drove in the city was the ring road so fairly free flowing but a bit of stop and go as well in the city. Stayed the night and returned home and not too many stops along the way each way but every restart and certainly every cold start sets it back for fuel mileage. Why I say that is I see some people will cherry pick a fuel mileage leg after the vehicle had been warmed up driveline wise before hand and its a forgiving ( easy rolling drive leg for example ) and call that their fuel mileage which can give a false perception of reality. I was not heavily loaded at all but never the less the flip bak cover, rubber bed mat, various tools etc and extra jerry cans of fuel all way up to a few hundred pounds of dead weight so its not an empty truck. The cold inflation tire pressures are set more near the freezing point so once they are warmed up driving I was showing 45 front and over 40 rear and realize high inflation pressures would help a little in fuel mileage but certainly not the ride on our crap sections of highway. The weather was good so was not raining as that can really drag mileage down, in fact I had a bit of a tail wind on average driving home. Most people on here would never have driven on that freeway to visualize it but its got a fair bit of rolling type of landscape with numerous river valleys. For the most part I had it on cruise set to 62 although kicking it off if I caught it in time before it started down shifting and self braking going down the grades. Most of the more substantial grades its shifting into 7th I believe as 8th just doesn't have it. Total distance round trip was 643 miles and my overall average and I did refuel three times in all, figured out to 17.65 miles per US gallon. My best fuel mileage section refuel within all of this figured out to 18.46 and these are all hand calculated figures. I find if anything that the trucks computer can be over optimistic, sometimes its pretty close but other times its stretching it. On paper persay in theory the truck would have just about made it on fumes for that whole drive without refueling once.    Which made me think of the topic thread of the wonder if these trucks could do 20 mpg and that is a good question, certainly would have to be on an easy going flat highway, no head wind, the right temperature, not packing around a bunch of dead weight and puttering along even slower than I was I would suspect and going steady and not stopping to smell the flowers or take a piss !. It probably is possible but not without effort to attain that with the wind resistance and weight of these trucks. Of course on my drive most people are passing me if they have the power as per loaded highway tractors, never mind a lot of speedy vehicles but the speed limit is 68 and most are at or well over that. 
    • Aimatdeer
      Ac not keeping up

      By Aimatdeer · Posted

      Monday looks like a good day for the dealer to test an ac issue. Hopefully it all turns out good.
    • CamGTP
      Gas Prices

      By CamGTP · Posted

      Paid $2.72 for E85 today.
    • Atlas
      Gas Prices

      By Atlas · Posted

      Welcome back! No, it definitely doesn't pass the sniff test. Even "ceasefire" needs an alternative definition these days.    $5.29 at Kroger today
    • bluev8
      Intermittent no-code issues on 2022.5+ V8 trucks — what did the shop fail to capture?

      By bluev8 · Posted

      That makes sense, and I think you are describing the real product problem. Capturing data is the easy part. If the owner or technician has to manually dig through five minutes of millisecond-level logs, the product has already failed. The device would be at the ECM harness, not at the OBD port, so I agree that data retrieval and event marking need to be thought through carefully. The way I am thinking about the architecture is: The recorder itself should not depend on a phone, app, Bluetooth, Wi-Fi, or cloud connection to capture the event. It should always keep a local rolling buffer and lock the event locally. A button, phone app, or small cabin device would only act as an event marker. If the driver feels a stumble and presses the button 10–30 seconds later, the pre-buffer has to already contain the useful data. For data retrieval, the practical options would be a sealed service USB lead, Wi-Fi download, or a phone/cabin companion device. I would not expect the owner to remove the ECM-side module or work with raw files directly. The cloud or AI side would be for interpretation, not for capturing the event. The truck may have no connection when the issue happens, so the evidence has to be saved locally first. After that, cloud processing could help decode the data, compare it against baselines, and generate a readable report. For the first version, I would keep the automatic triggers conservative and objective: driver event marker bus-off error passive voltage drop / brownout device reset FIFO or queue overflow a normally periodic message disappearing side-to-side communication mismatch, if the topology supports that For “learning normal,” I agree with your point, but I would not want to overclaim it as automatic root-cause diagnosis at first. A realistic first step would be learned baseline comparison for that specific vehicle and operating condition. For example, a value would only be compared against similar conditions: RPM range load / MAP throttle position gear / vehicle speed coolant and oil temperature battery voltage AFM/DFM state, if decoded and validated Then the report could flag things like: this periodic message disappeared compared with its normal timing this value deviated from this vehicle’s normal range under similar conditions the same abnormal pattern repeated after the same type of event the anomaly occurred together with voltage, oil-pressure, misfire, or communication changes But I would still call that “abnormal pattern detected,” not “replace this part,” unless there is enough validated repair data behind it. So the intended product would not be “here is a huge log.” It would need to be an event package: what triggered the capture how much pre/post data was preserved what changed before and after the event whether the device itself reset, overflowed, or saw a bus error selected graphs around the event raw data only as supporting evidence From your perspective, what would make this kind of report useful instead of just another datalog? For example: What are the top 5 parameters or events you would want highlighted first? Would you trust a learned baseline for that specific vehicle, or would you prefer fixed thresholds? How much false-positive flagging would be acceptable before you stopped looking at the reports? What would a one-page report need to show for an independent shop to take it seriously? For misfire, AFM/DFM, oil pressure, or U-code complaints, what would you want the tool to flag automatically?

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...