Possible answer to the weird vibration/stuttering

[ThatBossChevy21]

As I posted before I found that my u bolts were not tightened to spec from the factory on my 2021 trail boss. Since day one I’ve had the stutter or misfire type feeling at low rpms. I replaced the 2in block in the rear with 1in and tightened down the u bolts to around 80#’s. For two days now I haven’t had any of the issues I was having from before. GM told me that it could be that since the leaf springs were not properly tightened that it could have been sending vibrations down the frame thus setting off the knock sensors in which they were adjusting timing to compensate for the vibration cause intermittent misfires at low rpms. So maybe if your having this issue check your u bolt nuts factory stated 59 ft lbs with a 130 degree additional turn. Hope this helps others and hopefully fixed my issue.

Edited July 9, 2021 by ThatBossChevy21
Misspelled

[Liquid Plumber AT4]

4 hours ago, ThatBossChevy21 said:

As I posted before I found that my u bolts were not tightened to spec from the factory on my 2021 trail boss. Since day one I’ve had the stutter or misfire type feeling at low rpms. I replaced the 2in block in the rear with 1in and tightened down the u bolts to around 80#’s. For two days now I haven’t had any of the issues I was having from before. GM told me that it could be that since the leaf springs were not properly tightened that it could have been sending vibrations down the frame thus setting off the knock sensors in which they were adjusting timing to compensate for the vibration cause intermittent misfires at low rpms. So maybe if your having this issue check your u bolt nuts factory stated 59 ft lbs with a 130 degree additional turn. Hope this helps others and hopefully fixed my issue.

Great info.....gonna check mine on my AT4....thank you.

[03blackz71]

I have the same issue.   Low rpm vibration and slowing down to a stop vibration.

 

I just checked mine and they were loose.   Set my torque wrench at 55 ft/lb I got little over 1/4 turn.   Then did 65 ft/lb and then 75 ft/lb.     I could here it clamping down when I was tightening.  I will find out later if this helped me or not.

[ThatBossChevy21]

2 hours ago, 03blackz71 said:

I have the same issue.   Low rpm vibration and slowing down to a stop vibration.

 

I just checked mine and they were loose.   Set my torque wrench at 55 ft/lb I got little over 1/4 turn.   Then did 65 ft/lb and then 75 ft/lb.     I could here it clamping down when I was tightening.  I will find out later if this helped me or not.

Awesome! Let me know if it helped or not!

[fireaxxe]

Just got a new RST model, was smooth as silk. I added the GM Performance 2” lift (Trailboss suspension). After I added the 2” rear square block I now have a 25-20 mph rumble that I can hear more than I feel. It’s worse when braking. This is clearly a pinion angle issue. I will try finding a set of 2” tapered blocks and see if this solves the problem.

[4threeking]

I have the same exact issue. If you guys want to keep the factory blocks just order 2.5 degree shims. This will angle the rear diff so the pinion on the drive shaft is inline with the transmission. Chevy should have these included but it took me forever to figure out the issue

https://amzn.to/3pbzmdj

 

Throw these on your rear leaf springs and point the narrow end towards the front and the thick end towards the back. that should fix the issue.