8 Speed TSB update

Ron.s · February 28, 2015

Thinking about getting rid of my 2014 and getting the 6.2 with 8 speed. Has anyone had the recent update to the transmission program? Did it resolve the clunky shifting?

Sierra Matt · March 3, 2015

subscribed

Rme2513 · March 6, 2015

Read the topic

Anyone with a 2015 6.2l with the 8 speed auto?

I would wait if I was you

CounterMeasure · March 8, 2015

Read the topic

Anyone with a 2015 6.2l with the 8 speed auto?

I would wait if I was you

As some on their 2nd clunky transmission in less than 1800 miles, I second this advice. It'll be nice and smooth then first 100 miles and then slowly start going downhill from there. On this second one, I can hear almost every shift as a click if the music isn't up.

GM knows they've got a problem, but hasn't found the root cause yet.

Sierra Matt · March 9, 2015

I've got more than 3200 miles and the transmission shifts smoothly, but I do get the occasional clunk when taking off from a stop, and even more rarely on quick deceleration. If the radio is on its hard to hear. Sounds like loosness in the initial shift. We're it not for the occasional clunk it would be perfect. Just have not had time to take it in and when I talked with service manager he really wasn't aware of that problem with the new 8 speed, so it's like " what's the point of taking it in if they're not familiar with the issue.

brocka · March 9, 2015

I've got more than 3200 miles and the transmission shifts smoothly, but I do get the occasional clunk when taking off from a stop, and even more rarely on quick deceleration. If the radio is on its hard to hear. Sounds like loosness in the initial shift. We're it not for the occasional clunk it would be perfect. Just have not had time to take it in and when I talked with service manager he really wasn't aware of that problem with the new 8 speed, so it's like " what's the point of taking it in if they're not familiar with the issue.

Same situation here too for that first shift - occasional clunk when starting from stop and an occasional clunk when letting off the pedal if I'm going around 20-30 mph. Other than that, no issues and smooth shifting. Mine has 3100 miles on it.

Rme2513 · March 9, 2015

I'm in a new 15 with the 6 speed as a loaner and it dose not make the first sound so that means to me thAt something is not right with the new 8speed that cost more to get because it was "better"

CounterMeasure · March 9, 2015

Same situation here too for that first shift - occasional clunk when starting from stop and an occasional clunk when letting off the pedal if I'm going around 20-30 mph. Other than that, no issues and smooth shifting. Mine has 3100 miles on it.

Try cruising at 35mph in M5, then shift to M6. Then back to M5 a 5-10 seconds later. I wouldn't be surprised if those shifts are very audible clicks. The more miles I got on mine, the louder that shift got.

BluByU14 · March 9, 2015

Try cruising at 35mph in M5, then shift to M6. Then back to M5 a 5-10 seconds later. I wouldn't be surprised if those shifts are very audible clicks. The more miles I got on mine, the louder that shift got.

Same thing happened to me.......started with the initial acceleration/deceleration clunk....then moved to a clunk between 5-6.....now its almost every gear, however after the PI1388 (dont quote me on that exact TSB #) the initial clunk on acceleration has occured less and less, but the transmission now appears to be more and more lost in trying to find and hold the right gear.

BluByU14 · March 9, 2015

I'm in a new 15 with the 6 speed as a loaner and it dose not make the first sound so that means to me thAt something is not right with the new 8speed that cost more to get because it was "better"

Im in a 15 Tahoe with a 6-speed as a loaner right now and it runs SO much better that the 8-speed.

brocka · March 9, 2015

Same thing happened to me.......started with the initial acceleration/deceleration clunk....then moved to a clunk between 5-6.....now its almost every gear, however after the PI1388 (dont quote me on that exact TSB #) the initial clunk on acceleration has occured less and less, but the transmission now appears to be more and more lost in trying to find and hold the right gear.

http://www.gm-trucks.com/forums/topic/164949-anyone-with-a-2015-62l-with-the-8-speed-auto/?p=1572545

You are correct. PI1388. I will have them look at this at the same time they are doing PIT5374 for the headlights.

pm26 · March 9, 2015

Im in a 15 Tahoe with a 6-speed as a loaner right now and it runs SO much better that the 8-speed.

I wonder how good will be the 26 speed they are planning for the 2021 model. It will shift so often you will not even notice it, even if it jerks

Rme2513 · March 10, 2015

I wonder how good will be the 26 speed they are planning for the 2021 model. It will shift so often you will not even notice it, even if it jerks

That's going to be the new model coming out right is called the clunk o junk I heard

pm26 · March 10, 2015

All jokes aside, I think a good after market tune is your only option to get these to work properly. GM has got so wrapped up in maximum fuel economy numbers that they tuned these transmissions to go into the top gear as soon as possible, causing less than optimal shifting and sensation of the same.