2024 6.6 gas vibration and some other small things..

[TeamSaris]

18k on the best truck Ive ever owned and ive experienced a few things i thought might be of interest. 

 

Rear end "clunk" at slow speeds. Same thing ( i think) Pryme had on his truck. Leaf spring bushings. 

Secondly and more important. From day one, this thing would never coast. You were either accelerating or decelerating. You also had to HOLD it at a red light with the brake. She always wanted to go. Recently, it developed a "shudder" going up hills. Almost like a rumble strip. Its also a PIG on MPG. My fathers 6.6 gas 6 spd does way, way better. First the dealer diaged a misfire. Drove it again and still noticed the shudder. This time its a new torque converter, which to my mind really adds up with everything ive felt and most of it since day 1. 

Trailer lights and brakes are intermittent as hell. They replaced the whole plug assembly. We'll see. 

 

Its been an awesome truck otherwise. Can't wait to get it back. 

Towed a boat from upstate NY to Key West and back last fall. It did awesome!

[Pryme]

4 hours ago, TeamSaris said:

18k on the best truck Ive ever owned and ive experienced a few things i thought might be of interest. 

 

Rear end "clunk" at slow speeds. Same thing ( i think) Pryme had on his truck. Leaf spring bushings. 

Secondly and more important. From day one, this thing would never coast. You were either accelerating or decelerating. You also had to HOLD it at a red light with the brake. She always wanted to go. Recently, it developed a "shudder" going up hills. Almost like a rumble strip. Its also a PIG on MPG. My fathers 6.6 gas 6 spd does way, way better. First the dealer diaged a misfire. Drove it again and still noticed the shudder. This time its a new torque converter, which to my mind really adds up with everything ive felt and most of it since day 1. 

Trailer lights and brakes are intermittent as hell. They replaced the whole plug assembly. We'll see. 

 

Its been an awesome truck otherwise. Can't wait to get it back. 

Towed a boat from upstate NY to Key West and back last fall. It did awesome!

My clunk was only fixed because they replaced both full leaf assembly’s. Now it’s very silent. No sounds of any kind in the rear. 

[Another JR]

My 2021 3500 with a 1800 lb slide-in camper installed clunks a little when I hit the third stage springs going over bumps, but other than that the rear springs are still quiet. 

Edited October 16, 2025 by Another JR

[SoCal Angler]

Is this the Service bulletin regarding the rear leaf springs.....?

 

See attached

GM Rear Spring Bulletin.pdf

[Pryme]

10 hours ago, SoCal Angler said:

Is this the Service bulletin regarding the rear leaf springs.....?

 

See attached

GM Rear Spring Bulletin.pdf 125.24 kB · 7 downloads

Yup. Had that bandaid done and it lasted two months.  They wanted to do that again on my truck but since I was a month from having it 36mo I said no I want the leafs replaced because that fix will fail when I’m out of warranty and they contacted GM and they got approval to do the leaf springs since my sound was coming from both sides.