Hey yall, I have some 3 inch Superlift blocks lifting my rear end, and recently I drove to Houston (around 500 miles) and back. On the way back I began to notice that every time I stopped accelerating, like on a down hill grade, I would feel two little kicks, and it's only when slowing down. I talked to a guy at Advanced Auto because i was buying some parts and he said it happens a lot due to the drive shaft angle being changed when lifting with blocks. I guess my question is, what can I do about this? I think I could swap my U-Joints, but that's only a temporary fix.

I was also told I could purchase some angled shims to install underneath the blocks to fix the angle? How would I do this i.e. where would the high side of the shim face? Also where can I get some?

Any light shed on this matter would be awesome!!

 

first you need to get the oem specs on the existing driveshafts, u-joints and diff regarding max & min pinion angle.

With the truck leveled, you need to measure with an angle finder each of the angles at the u-joints, at the suspensions max/min travel points.

Now you will know if you are in range or not and then you can either use shims (for small changes no big deal) or the typical best solution is to change the u-joints that are designed to operate in the exiisting range.


but is this the real issue, I don't know, it sounds like there may be something else going on...an inspection is needed.

 

For real guys?! COME ON! update: the rough country blocks I got are angled, so the differential - drive shaft joint is fine I believe. The tranny - drive shaft may be the problem, and U-joints may be bad. I'm takin it to Scott's friday to have 'em look at it. hopefully i dont have to replace u-joints every week.....

help?!

 

I had the same problem once and the problem was the blocks were in backwards.
I took it to a spring shop to have the springs beefed and they put them in reverse.
Put them in so that tie pinion (u-joint) is tilted upwards and you should be good to go.

 

so the tall side of the block needs to be toward the front of the vehicle or the rear? also, when they put it in backwards was it immediately noticable? I didn't notice mine until i took a really long drive. thanks for the help by the way!

 

Tall side to rear!

Check your axle U-bolt's torque as well, make sure the rear axle isn't moving agaisnt the springs, etc.

Do you have a single piece rear drive shaft or does your's have a two piece with center carrier bearing?
With a two piece shaft, that's in the rear portion of the drive shaft. With a one piece, that's at the rear of te transmission (2WD) or transfer case (4WD).

Either way, 3" more lift is gonna pull the slip joint further out so less engagement between the two parts. If pulled out too much, it's easier that the two portions become "****ed" (crooked / misalligned) and soon, with some wear, a ridge developes where the two halves ends rest in normal driving.

In a good set up where the two halves have long engagement, there's little or no movement between them in rotation, only when absorbing or stretching for bumps, dips, etc. When pulled out too far, when not so deeply engaged, they will move against each other even in rotation on a smooth roadway. You'll also pick up a driveshaft vibration as the now worn and missaligned slip joint lets the shaft act more like a jump rope.

If that's your problem, it'll only get worse.

If that's your problem, what you may be feeling / hearing is the partially "****ed" (crooked / misalligned) and the misalligned halves popping back and forth over worn ridges in the slip joint as the rear axle housing rotates under acceleration / deceleration / braking.

If too short for proper engagement of the slip joint, only cure is drop truck or make longer shaft or move rear axle forwards a hair.

 

how many miles on your truck? could just be worn out u-joints and it showed up with a slight change in pinion angle.

chances are your DS is fine, most here don't mess with driveshafts until they hit the 8-10" lift height.

if you are unsure if everything is right, post a picture of the block installed, and both ends of the DS and some one will tell you if everything is correct.

 

well i took it to scotts. turns out, my u-bolts were loose. with the brakes on, they went forward, and revers and the axle was twisting like a mother. I dont have a ratcheting gun, so they torqued em down hard core for me. Took it on the highway and it's all good! only thing i still notice a little bit of a vibration. U-joints are fine, for now, but the angle between the transmission and drive shaft is a LITTLE off. I was told i can get a kit to lower the transmission a bit for pretty cheap but it will be hard to find. all's good now though! thanks for the help

 

Glad you got it fixed!