Who has the Chevy 8sp transmission?

[KJQ6945]

In 2018 I bought a new Silverado 1500. 6.2 v8 with an 8sp transmisson. It’s been an excellent vehicle. lately, it’s developed an issue. Between 50 and 70, it intermittently feels like you are driving over rumble strips. A little Google search reveals this is a common issue, and GM is being sued over it. Who knew?

anybody else have this issue?

 

[gll]

My 2021 Colorado 3.6L has the 8L45 transmission... Is that the problematic one?

 

[gll]

"8-Speed GM Transmission Problems Fixed Via New TSB | GM Authority" https://gmauthority.com/blog/2019/0...speed-automatic-gm-transmission-problems/amp/

 

[KJQ6945]

My 2021 Colorado 3.6L has the 8L45 transmission... Is that the problematic one?

Yes sir, I believe so. It appears that the trans is in the Corvette, Camaro SS, Silverado and the Canyon.
Google lists plenty of threads on complaints. Have you had any issues?

 

[gll]

I barely have 4000 miles on it, but the one issue I've had is with a load of feed over 4 or 500lbs. Then it shudders at 40 or 50mph..., badly

My ex-Chevy mechanic brother thought it might be poor differential alignment, but this makes me wonder. I've been waiting until my first oil change to have Chevrolet look at it, but I might address it sooner!

 

[KJQ6945]

I barely have 4000 miles on it, but the one issue I've had is with a load of feed over 4 or 500lbs. Then it shudders at 40 or 50mph..., badly

My ex-Chevy mechanic brother thought it might be poor differential alignment, but this makes me wonder. I've been waiting until my first oil change to have Chevrolet look at it, but I might address it sooner!

The shudder basically boils down to a torque converter lockup issue. If you google it, there’s lots of information. I’m taking mine to the dealership in the morning. Just wanted to see what TGT knew first.

 

[lonestardiver]

The fix is to replace the transmission fluid per the TSB. The original fluid is hydroscopic and absorbs water. Had this done on my truck and the problem went away. GM/Chevy dealers have a special machine to do this fuild swap. Mine had a very noticeable shudder that was only apparent when the transmission temp got to 170 degrees or so.

 

[Brains]

I had the issue in my old Camaro as well, it's the lockup clutch not being applied with sufficient pressure in an attempt to try and save fuel. Early on before they understood what the cause was, they first did a converter under warranty. Fixed it for a while. The shudder came back, so they did a fluid change which again fixed it for a while. The shudder was still there with the different fluid, but not nearly as pronounced and it didn't occur until the trans temps came up.

 

[KJQ6945]

The fix is to replace the transmission fluid per the TSB. The original fluid is hydroscopic and absorbs water. Had this done on my truck and the problem went away. GM/Chevy dealers have a special machine to do this fuild swap. Mine had a very noticeable shudder that was only apparent when the transmission temp got to 170 degrees or so.

How long ago did you have the transmission flushed?
Lots of people complaining online that the flush is just a temporary fix, and the issues return.

I’m hoping that the fluid change eliminates the problem permanently, but I’m a little skeptical.

 

[Brains]

If you want a permanent fix, find a good performance shop that deals with GM vehicles. They can update the TCM calibration to change the lockup clutch apply strategy and permanently fix it. The downside is it will void the warranty on the transmission.

 

[KJQ6945]

I had the issue in my old Camaro as well, it's the lockup clutch not being applied with sufficient pressure in an attempt to try and save fuel. Early on before they understood what the cause was, they first did a converter under warranty. Fixed it for a while. The shudder came back, so they did a fluid change which again fixed it for a while. The shudder was still there with the different fluid, but not nearly as pronounced and it didn't occur until the trans temps came up.

This seems to be the consensus, from what I’ve read. No real fix available from Chevy.

 

[KJQ6945]

If you want a permanent fix, find a good performance shop that deals with GM vehicles. They can update the TCM calibration to change the lockup clutch apply strategy and permanently fix it. The downside is it will void the warranty on the transmission.

I’ve got about 4K miles left on my warranty, so it’s going to the dealership for now, then I’ll seek aftermarket solutions.

 

[Axxe55]

This isn't exactly a new issue either. Back many years ago working in GM and Dodge dealerships, both were having very similar issues of "shuddering" going back to the early 2000's.

Several things were tried to correct the problem. There were several TSB's put out relaying various methods to correct the problem.

Changing fluids was one. Doing a software upgrade to the PCM. Converter replacement, and even in some cases, complete transmission replacement in extreme cases.

Even my brand new at the time 2005 Dodge Ram 1500 was doing the same thing.

 

[Eli]

On the Ford Crown Vics I used to drive, a shuddering converter was just a reminder the fluid needed changing!
I'm actually looking into buying a GM with the 8-speed: A GMC Savana full-size 12-passenger van with the 2.8 DuraMax and 8-speed! Aside from this shudder issue, do the 8-speeds hold up well?

Eli

 

[KJQ6945]

On the Ford Crown Vics I used to drive, a shuddering converter was just a reminder the fluid needed changing!
I'm actually looking into buying a GM with the 8-speed: A GMC Savana full-size 12-passenger van with the 2.8 DuraMax and 8-speed! Aside from this shudder issue, do the 8-speeds hold up well?

Eli

I’m sitting at 56K miles on it and have nothing bad to say about it, until now.
Its been a solid performer, and has been impressive on the fuel economy.
Wife’s ‘19 Tahoe has the 5.3 and the 6sp, and her fuel economy doesn’t compare to mine. But hers doesn’t shudder either.

 

[Brains]

The box itself is quite good, very strong and reliable. The only downside is the converter lockup which can be quickly and easily tuned out. Heck you can do it yourself with HP Tuners and similar tools, if you're so inclined. Simply zero out the allowable TCC slip in 7th and 8th gear (factory set to 10rpm in low load ranges). Be warned though, if the converter is shuddering a lot the tune may not fix it, as the friction material will eventually break down. They've also revised the converter to help, not sure what they changed though.

 

[pronstar]

I think the factory fixes are band-aids at best.

Know several people who had the issue, dealer fixed, only to come back soon after.

The worst one was my buddy’s GMC Sierra Denali. Damn nice truck, but with a tranny from a garbage truck. He never could get it to shift right…but it was recently stolen, he got more than he paid, and now has a 10-speed tranny in his 2021 replacement - zero issues.


Sent from my iPhone using Tapatalk Pro

 

[lonestardiver]

How long ago did you have the transmission flushed?
Lots of people complaining online that the flush is just a temporary fix, and the issues return.

I’m hoping that the fluid change eliminates the problem permanently, but I’m a little skeptical.

It was about 4K miles ago. Truck is a 2018 GMC Sierra SLT Z71 and has 69k miles on it.

 

[Axxe55]

I remember back in the early to mid 2000's, this seemed like a prevalent issue among several GM car lines, and Dodge was having some similar issues with the Ram trucks as well.

Did any Ford vehicles from that time period have similar issues?

 

[candcallen]

Just for info, the newer 10 speed tranny was developed by both ford and gm and both use it.

I dont like it as I think it shifts too much but that's my only complaint. My expedition is the 3rd vehicle I've had with it.