Help troubleshoot before service appt

michigan2500hd · May 31, 2018

I know there are numerous threads about the 8 speed however it seems overwhelming and new posts get lost in 100's if other posts.

I'm taking my 2015 6.2 max tow in June 4 th for trans troubleshooting.

Been in the shop a couple times for issues with said trans only to get 2 updates done and I'm told some of the issues are just the trans doing... blah blah blah. Many of you have heard the same excuses from various dealerships.

Had the delay going from reverse to first update and it helped that issue.

Had a shift flare update done and it helped for a week then it came back with available a vengeance.

I was told my issue with the truck not downshifting into first unless stopped was normal. I call bull on that one. Say you do a rolling stop the trans will still be in 3rd... No power and dangerous because I have to go into manual mode and click it down to first.

No I've got a shutter right after most shifts that feels like you ran over a rumble strip.

Should I request a new torque converter? New trans?

I have about 35,000 miles and some warranty of some kind to left I know it's not the bumper to bumper though. Any advice?

Sent from my SM-N950U using Tapatalk

xMEATxHAMMERx · May 31, 2018

I know there are numerous threads about the 8 speed however it seems overwhelming and new posts get lost in 100's if other posts.
I'm taking my 2015 6.2 max tow in June 4 th for trans troubleshooting.
Been in the shop a couple times for issues with said trans only to get 2 updates done and I'm told some of the issues are just the trans doing... blah blah blah. Many of you have heard the same excuses from various dealerships.
Had the delay going from reverse to first update and it helped that issue.
Had a shift flare update done and it helped for a week then it came back with available a vengeance.
I was told my issue with the truck not downshifting into first unless stopped was normal. I call bull on that one. Say you do a rolling stop the trans will still be in 3rd... No power and dangerous because I have to go into manual mode and click it down to first.
No I've got a shutter right after most shifts that feels like you ran over a rumble strip.
Should I request a new torque converter? New trans?
I have about 35,000 miles and some warranty of some kind to left I know it's not the bumper to bumper though. Any advice?

Sent from my SM-N950U using Tapatalk

Power train warranty I think is 3 years/36k miles... What ever you do, you better get it fixed within the next 1k miles! Or buy yourself an aftermarket warranty...

I had a 2015 ltz with that stupid transmission... I traded the ****er in with about 15k miles on it! I had a constant hesitation from the tranny and a highway speed shimmy from hell.

Sent from my SM-G955U using Tapatalk

michigan2500hd · May 31, 2018

I think I have a GM certified warranty until 41000 but who knows what that covers. Forgot to mention I put it in drive the other day and it just revved.. No go for a couple seconds. I love the truck but dang it's like it was only half engineered.

xMEATxHAMMERx · May 31, 2018

I think I have a GM certified warranty until 41000 but who knows what that covers. Forgot to mention I put it in drive the other day and it just revved.. No go for a couple seconds. I love the truck but dang it's like it was only half engineered.

My 2017 was just in the shop with an error message at 5k miles... I don't know what's happened with GM recently, but damn!

Sent from my SM-G955U using Tapatalk

TXGREEK · May 31, 2018

I think I have a GM certified warranty until 41000 but who knows what that covers. Forgot to mention I put it in drive the other day and it just revved.. No go for a couple seconds. I love the truck but dang it's like it was only half engineered.

You can check on the term of your warranty by calling service department and having your VIN# handy

Sent from my iPhone using Tapatalk

TXGREEK · May 31, 2018

I know there are numerous threads about the 8 speed however it seems overwhelming and new posts get lost in 100's if other posts.
I'm taking my 2015 6.2 max tow in June 4 th for trans troubleshooting.
Been in the shop a couple times for issues with said trans only to get 2 updates done and I'm told some of the issues are just the trans doing... blah blah blah. Many of you have heard the same excuses from various dealerships.
Had the delay going from reverse to first update and it helped that issue.
Had a shift flare update done and it helped for a week then it came back with available a vengeance.
I was told my issue with the truck not downshifting into first unless stopped was normal. I call bull on that one. Say you do a rolling stop the trans will still be in 3rd... No power and dangerous because I have to go into manual mode and click it down to first.
No I've got a shutter right after most shifts that feels like you ran over a rumble strip.
Should I request a new torque converter? New trans?
I have about 35,000 miles and some warranty of some kind to left I know it's not the bumper to bumper though. Any advice?

Sent from my SM-N950U using Tapatalk

What you’re experiencing is typical service department stupid is as stupid does mentality. Try going to multiple dealerships before you just except their answer. I had a 16 DMax with steering issues from the get go, always seemed to be over steering due to the electric assist and just couldn’t drive in a straight line without correcting the steering. Ok, took it multiple times to dealer and each time BS excuse. Finally called GM and made it very well known of my being unhappy as well as unsafe while driving. GM responded, had dealership swap out 16 steering box for new updated 17 unit plus lots of updates. GM customer assistance # 1-866-790-5600. Please make sure to let them know you’ve been having issues for years and no one has resolved it.

Sent from my iPhone using Tapatalk

Tahoe02 · May 31, 2018

Your warranty is 3yr/36,000 bumper to bumper and 5yr/100,000 power train. I think tranny issues are handled like this. computer update, tranny fluid change, torque converter replacement and then tranny replacement. You may want to file a complaint with GM and the last resort is to check your states Lemon Law.

TXGREEK · May 31, 2018

I think I have a GM certified warranty until 41000 but who knows what that covers. Forgot to mention I put it in drive the other day and it just revved.. No go for a couple seconds. I love the truck but dang it's like it was only half engineered.

That’s definitely sounds like a program issue. Get it checked out and see if you can get the latest updates

Sent from my iPhone using Tapatalk

TXGREEK · May 31, 2018

I think I have a GM certified warranty until 41000 but who knows what that covers. Forgot to mention I put it in drive the other day and it just revved.. No go for a couple seconds. I love the truck but dang it's like it was only half engineered.

Almost forgot, Certified vehicles generally come with 100K warranty. I know this cause they certified my 16 DMax when I traded it in for my 18 and the dealership told me they give 100K warranties on all their certified units

Sent from my iPhone using Tapatalk

michigan2500hd · June 1, 2018

When I explained the issue over the phone to the service writer he said he wasn't aware of a updated tourque convertor and had never heard of a triple flush. Oh great. I hate to take it somewhere I didn't but the truck from. You tend to get better service at the place of purchase as a general rule I think. Too bad they may not be all that knowledgeable.
I think when I drop it off I'll request a mechanic ride-a-long.

Sent from my SM-N950U using Tapatalk

michigan2500hd · June 1, 2018

I swapped out 20" wheels and 33" tires to 18" factory size so they can't blame anything else. I have to say it makes the trans even worse. Thought it would be the opposite.
Only thing not stock now is the Magnaflow muffler and blocks in the rear. Along with the Bilsteins.

Sent from my SM-N950U using Tapatalk

Colossus · June 1, 2018

1 hour ago, michigan2500hd said:

When I explained the issue over the phone to the service writer he said he wasn't aware of a updated tourque convertor and had never heard of a triple flush. Oh great. I hate to take it somewhere I didn't but the truck from. You tend to get better service at the place of purchase as a general rule I think.

On the contrary, I believe in taking the truck to the place that knows trucks best. That will not always be the dealership you purchased from. Some dealerships have better truck techs and techs that do a better job at diagnosing than others.

mjm-1957 · June 2, 2018

The powertrain warranty on a 2015 is 5 years ,100,00 miles.The eight speed M5U has been a problem since it came out in 2014. I am the transmission guy at a GMC -Buick dealer and hate that transmission. It was released before it was ready and left in the hands of the dealer mechanics to try and fix what GM should have straightened out before releasing this horrible transmission. I don't know if all the complaints can ever be satisfactorily repaired. Too many bandaids thrown at a pisspoor design. I have been replacing valve bodies that have been on national backorder and damn near impossible to get to try and fix some shift issues. The tcc shudder is another problem with this transmission. Only the canyon and colorado get the triple flushes now. The rest get one flush and out the door.Good luck with that repair.Update after update and fast adapt learns and on and on and on.Don't know what the answer is?Maybe the ten speeds will be better.......

TXGREEK · June 2, 2018

The powertrain warranty on a 2015 is 5 years ,100,00 miles.The eight speed M5U has been a problem since it came out in 2014. I am the transmission guy at a GMC -Buick dealer and hate that transmission. It was released before it was ready and left in the hands of the dealer mechanics to try and fix what GM should have straightened out before releasing this horrible transmission. I don't know if all the complaints can ever be satisfactorily repaired. Too many bandaids thrown at a pisspoor design. I have been replacing valve bodies that have been on national backorder and damn near impossible to get to try and fix some shift issues. The tcc shudder is another problem with this transmission. Only the canyon and colorado get the triple flushes now. The rest get one flush and out the door.Good luck with that repair.Update after update and fast adapt learns and on and on and on.Don't know what the answer is?Maybe the ten speeds will be better.......

Maybe, maybe not....

Sent from my iPhone using Tapatalk

michigan2500hd · June 8, 2018

So after the truck sat at the dealer Monday through Thursday without them looking at it I just got a call Friday at 5 saying it's ready to pick up.. They close at 6.
The service advisor said they were able to duplicate what the trans was doing. ( I'm surprised and impressed)
Said they dropped the trans pan and flushed the trans and the lines. Hope they did a reverse flush.
They changed the filter and then replaced the fluid with Mobile One trans fluid. That's the other part that worries me. Is that kosher?? Sends like they'd use GM fluid that's recommended for the 8 speed. Hmm well maybe it will be a better choice idk.
Dealer said this is the first 8 speed they've done this to. ( This worries me as well)
He also said while they were working on mine another 8 speed came in with same or similar issues so they know the bulletin to look for now.
I'll pick it up in the morning and see how it does.
I was cool with them not getting it fixed right away since they have me a loaner truck. 2018 Sierra with a 5.3. I did however really miss the power of the 6.2.
It's nice having a loaner truck to keep miles of mine.

Sent from my SM-N950U using Tapatalk