2017 Yukon Denali Shudder Problem

Quick update: I took the car back to CarMax, and they sent it to a GMC dealer. The dealership said they’ve never seen a shudder this bad before and will be replacing the transmission.

GMC also wants to replace some rear suspension components, bringing the total cost to a little over $10k. Frustrating, but I’m hopeful that the car will run smoothly after these fixes.

Fortunately, CarMax is covering all the costs.

It's good that Carmax stepped up and is fixing it, but pretty bad that GM transmissions are such crap these days.

tom3 said:

It's good that Carmax stepped up and is fixing it, but pretty bad that GM transmissions are such crap these days.

Click to expand...

I was surprised. The service tech and manager were on top of it, which was unexpected. Plus, they ordered all new brakes and rotors and are replacing all four tires. The service tech has been calling me almost every day with updates.

Yeah it's our first GMC vehicle.

I literally signed on this morning because we started to experience the shutter recently. It actually had the shutter when we bought it 6 years ago with about 60k miles on the clock. Took to my local dealer where a buddy of mine works, he did the flush, and haven't had a problem since.
In the last week or so the shutter has become more prominent. I'm really hoping a fluid flush, filter change will do the trick but I'm preparing for a possible TC change.
I haven't noticed any issues with the operation of the transmission yet, just the shutter. What are the odds the transmission could need to be rebuilt? And how much are good shops typically charging for this. I have the 8 speed.

JMH1980 said:

If you have a dipstick to check fl you I'd level, it's probably a 6L80 Transmission. The vehicle is going into a safety lock up because there are internal problems. I'm not an expert, but might be looking at a rebuild/replace situation, from what I've read on other threads.

Click to expand...

This seems like the right answer. My mechanic despite knowing this was likely a transmission issue, just drove the vehicle then recommended I take it to our local transmission expert. Should have done that to start, since I waited 10 days for the appointment.
The local trans experts had the truck evaluated pretty much the day I dropped it off (Friday afternoon and got a call Monday before noon). "The whine you are hearing is the pump and probably will need a rebuild. $500 for us to drop the trans and check things out. If you continue with the needed work the $500 applies". I will know more tomorrow...or maybe later today.

kk1lron said:

This seems like the right answer. My mechanic despite knowing this was likely a transmission issue, just drove the vehicle then recommended I take it to our local transmission expert. Should have done that to start, since I waited 10 days for the appointment.
The local trans experts had the truck evaluated pretty much the day I dropped it off (Friday afternoon and got a call Monday before noon). "The whine you are hearing is the pump and probably will need a rebuild. $500 for us to drop the trans and check things out. If you continue with the needed work the $500 applies". I will know more tomorrow...or maybe later today.

Click to expand...

There are some upgrades for the 6L80. From my research for my own transmission, an 8L90, I've found thG Transgo and Sonnax have kits for the GM platforms. Also recommended to upgrade the converter to a billet at the very least. Whether you keep it at the stock specs or increase the stall, is up to you. Slightly higher stall converter can be fine for stock applications.

JMH1980 said:

There are some upgrades for the 6L80. From my research for my own transmission, an 8L90, I've found thG Transgo and Sonnax have kits for the GM platforms. Also recommended to upgrade the converter to a billet at the very least. Whether you keep it at the stock specs or increase the stall, is up to you. Slightly higher stall converter can be fine for stock applications.

Click to expand...

Just got the call from the trans folks. Full rebuild. With "upgrades", TC, etc, etc. $7k. Ugh.

kk1lron said:

Just got the call from the trans folks. Full rebuild. With "upgrades", TC, etc, etc. $7k. Ugh.

Click to expand...

Work complete! Super fast TAT. The shop is FULL aware of all the upgrades and has applied them. They have been doing lots of 6L80s (I think he said 5 a month) and keeps all the parts in stock. Happy about the service. Barry's Transmission Specialists, South Burlington, VT.

I should add that after the rebuild I no longer hear a short skreetch at startup. That had been reported as a starter noise by some on "the Internet". Maybe it was my transmission?? Or maybe reassembling the trans to the engine squared that away?? Not complaining

Son had about the same experience, little cheaper here in Applachia. Shop owner said it used to be Mopars that kept him busy, now it GMs with the 6 and 8L failures. So far his has been perfect.

kk1lron said:

Work complete! Super fast TAT. The shop is FULL aware of all the upgrades and has applied them. They have been doing lots of 6L80s (I think he said 5 a month) and keeps all the parts in stock. Happy about the service. Barry's Transmission Specialists, South Burlington, VT.

I should add that after the rebuild I no longer hear a short skreetch at startup. That had been reported as a starter noise by some on "the Internet". Maybe it was my transmission?? Or maybe reassembling the trans to the engine squared that away?? Not complaining

Click to expand...

I have driven about 150 miles on the rebuilt trans. I pretty consistently get a short "weeep" (1/2 second ish) when gently accelerating from about 33MPH after having slowed gently from about 40MPH. I do not hear this at any other similar speed transition. I called the rebuild shop and was told it is the TC clutch reengaging and that it could take 1000 miles before that goes away. I also figured that is where the noise originated, but wonder if the "wait 1000 miles" comment is valid or not.