2016 5.3L 8 speed shudder/vibration

SierraMyst · January 3, 2016

Ok...so I know you all are going to think I'm crazy, but every time I've driven the truck for the last two weeks has been on the highway at high speed, or stop and go traffic light to traffic light. But I had to drive into work today and traffic was horrible.

We were slow rolling from about 18 - 30 repeatedly.

I'm experinong issues similar to the items address in bulliten/recall 15389 that was targeted at the 8 speed 6.2L Sierras. Mine transmission is shuddering/vibrating in slow traffic. Specifically around 25 miles an hour when the rpms drop to 1000.

Acceleration to 1250 rpms shakes and shudders the truck like driving over rumble strips.

It's like the transmission isn't downshifting correctly and it's shuddering from being in a higher gear. It's at about 25 mph at 1250 rpms. Then when you let off the gas, it drops to 1000 rpms/20 mph. As soon as you give it a little gas the drive train rumbles/shudders/vibrates until it gets up to 1250 rpms or more. It's like it's holding at 3 gear and that gear is too high to accelerate from kinds of like driving a stick shift and shifting into a too high gear.

If slow down below 18 mph, I can feel the shift, and then it doesn't do when speeding back up. The shift back to 3rd is hard than usual, but it won't vibrate.

It also happens around 40 miles an hour if your cursing. The rpms sit at about 1500. If you take your foot off the gas and slow down the rpms will drop to about 1000, and accelerating back up it will do it again, but not as pronounced as at 25 mph shudder.

Again I am almost certain that the transmission isn't down shifting as quickly as the rpms drop. It's holding onto higher gears for too long.

I can't stress enough that just regular smooth driving from a stop light, the shifts bring the rpms to 1500 or higher. So all the shifts are smooth. Cruising at 70 mph is butter smooth. This is just when there a slow down that drops my rpms and the truck doesn't down shift.

I know there was a reprogram for the 8 speeds, but until now, only 6.2L engine had an 8 speed. The 2016 5.3L now has the 8 speed as well.

GMC chat says that the 15389 recall doesn't apply to 2016s. But I was certain it applied to every other 8 speed GM manufactured at the time.

I'd hate to think that there's an issue with truck's tranmission at 300 miles. It's pretty frusting when you live in DC where theres non stop slow and go or slow rolling traffic.

So I'm going to take it in, but I'm hoping for some insight or someone else with a new 2016 5.3L that can confirm this.

Thanks in advance.

ScreaminChevy · January 3, 2016

Sounds like torque converter is slipping when it should be locked up.

Edited January 3, 2016 by ScreaminChevy

SierraMyst · January 3, 2016

Sounds like torque converter is slipping when it should be locked up.

Is that pretty common. Sounds like the issue the 6.2L 8 speeds were having.

SMiller · January 3, 2016

Try it in tow/haul.

Sounds to me like the torque converter is staying locked, if bogging the motor it will shake.

Edited January 3, 2016 by SMiller

tonygxp · January 3, 2016

i have the same truck. put the DIC to any of the fuel screens (trip A or B or instant economy) and take notice of the V8 /V4 symbol.. mine does that at very light or no throttle and i noticed it's the AFM causing it which now DOESN'T bother me, knowing it's designed to be that way.. hopefully that's what your feeling. I've felt the 6.2 trans issues and they're nothing like what I have (or from what it sounds like you are dealing with imo)

SierraMyst · January 3, 2016

i have the same truck. put the DIC to any of the fuel screens (trip A or B or instant economy) and take notice of the V8 /V4 symbol.. mine does that at very light or no throttle and i noticed it's the AFM causing it which now DOESN'T bother me, knowing it's designed to be that way.. hopefully that's what your feeling. I've felt the 6.2 trans issues and they're nothing like what I have (or from what it sounds like you are dealing with imo)

Ive watched the V4 to V8 switch. I know the slight tremble you're speaking of and that doesn't bother me.

This really does feel like it's in a higher gear. If I slow down more than normal, I feel it down shift and the shudder doesn't occur.

Every time, about 30 times today, if I only slowed to 20 mph and the rpms didn't get low enough to down shift, the shudder was present accelerating back up to 1250 rpms.

It's crazy. It only happens in the 1000 to 1250 band, everytime. Where as the AFM can be felt across the band depending on my light foot.

Edited January 3, 2016 by SierraMyst

SMiller · January 3, 2016

Drop down to M6 so the V4 can't kick on, although I know you said it wasnt the problem.

At the end of the day it is the shit tuning that is causing your problem.

diyer2 · January 3, 2016

I have always taken my auto's out of the highest gear while driving in the city. My six speed I run in M5 or M4 depending on traffic.

f8l vnm · January 3, 2016

Most of these issues are tune related. Good luck

relsoc · January 3, 2016

I'm sure it's a tune issue. Eventually there will be a TSB for a software update. I'll keep an eye out for it and post here when it happens.

I feel the same shudder at times as well.

SierraMyst · January 3, 2016

No traffic this morning, so no issues on the highway.

But getting off the highway off ramp at about 30 mph, I let off the gas. Rpms dropped to 1000, and sure enough, accelerating out of the ramp.....rumble, runble, rumble.

On a side note...drop from stop light once in town with tow mode on. The higher shift point were flawless. That's where the truck should he shifting in slow and go traffic.

I hope there's reprogram TSB. Dealer says to bring it in and let them look at it, especially since I can duplicate it. Even if there's nothing on the books from GM, it will get them started on a case that will help build a recall or service bulliten.

Hopefully all the other 2016 8 speeds with the same issue can do the same.

SMiller · January 3, 2016

That's why I drive in tow/haul, it puts the shift points where they should be, having the motor bogged down does not help mileage and is hard on the drive train.

GMC-AT · January 3, 2016

my 2016 8 speed has 1K miles now... it was pretty sloppy in traffic for the first 300 miles.. but has already started to improve. I'm sure it will be even better by the time I get to 5K.

AgDoctor · January 3, 2016

I have a 2016 5.3 with the 8 speed, and it has about 600 miles on it. No issues with it that I can tell, and I am pretty sensitive to shutter( had an old 97 Z71 I had to add friction modifier to trans fluid). I like it so far.

Sent from my SM-N910V using Tapatalk

SierraMyst · January 3, 2016

I have a 2016 5.3 with the 8 speed, and it has about 600 miles on it. No issues with it that I can tell, and I am pretty sensitive to shutter( had an old 97 Z71 I had to add friction modifier to trans fluid). I like it so far.

Sent from my SM-N910V using Tapatalk

Try cruising at 25 mph. The rpms should be at 1250 to 1500. Let off the gas like slowing down in traffic and let the rpms drop to 1000 and give gas again lightly and front the rpms to 1250.

Just duplicate rolling in traffic from 18 - 25. Slow, go, slow, go, slow go.

Let me know if you feel amything.

If you go below 18 mph, it will down shift and not shudder on the way back up.