21 Rst shudder / wobble feeling after level

[Ry363]

So my 21 rst 6.2 drove good stock (except for the bouncy Rancho shocks) Just installed Icon stage 2 kit, icon 17” wheels with Mickey Thompson exp 295/70 tires. Front is set just under 3” taller over stock, don't think the cv angles look bad. After driving it especially around 65 or so, you can feel it in the seat and floor of the truck kind of shaking. Next day installed readylift 2.25” rear lift block. Truck was re aligned. Tires we’re road forced balanced and shuddering / shaking is still there. Maybe even worse than before rear lift block. Can feel it at low speeds decelerating and really around 65. Truck has 2500 miles on it now. Read other threads maybe pinion angle? Torque converter?  Did not have factory leaf spring shims. When I have time going to swap back to factory wheels / tires to eliminate the chance of a bad new wheel or tire. 
had a very similar set up on my 2018 same size wheel / tire combo with no issues. Anyone else have similar issue after level?? T1 trucks more sensitive to driveline angles?? 

[tomthetrex]

I have the same Icon Kit with no issues. I have a factory trailboss block installed in the back.

 

Have they retorqued everything to make sure nothing is loose?

 

 

[Ry363]

I’ll have to check what it’s all torqued at this evening. Did your truck come with a factory shim under the leaf springs? Just looked at my dads 2019 with the same icon kit (only added 1” rear block) but his has the factory shim. 
 

[CamGTP]

I'll put a dollar on the tires, maybe I'm right or maybe I'm wrong. Let us know what you find out.

[tainoxl]

I just did 2" level and Trail-boss replica 20s on 33x12.5 tires , Road-force balanced, new alignment and now I have the wobble shutter feels like from rear end.  Put the stock 18" with 265/65 tires and it goes away.   We tried three different tire even a general grabber lt tire in 275 55 20 and same issue.   I was told possible drive line issue and go see the dealer or Mechanic.  Not sure how much money I want to keep throwing at this.  I know dealer will cry about putting it to stock and then trouble shoot but it feels smooth with the stock 18s.

[Ry363]

Life keeps getting in the way of putting the stock wheels/tires on lol. Part of my problem just found out week ago they installed the rear lift blocks backwards. There tapered. I switched them around and low speed rumble got better especially when I would brake at 40. Still wobbles at 65ish pretty bad. Placed that installed my kit is going to try adding 1 degree pinion shim see what that does. Maybe a bad wheel or tire(s). Very annoying.

[tainoxl]

^Yes it is,  50k truck you cant upgrade wheels and tires cause it shakes.  Not only that but if the driveline angles are that far off from factory its going to wear parts and bearing fast.