Degree shims question.

So Im finishing up my Rustys 6.5 short arm lift, for the rear I opted for the 4.5 spring and 1.5 shackle. The kit also came with 6* shims, after some searching I decided that using the shim to aim the pinion up towards the transfer case.


Now it is time to start torquing everything down so i decided to double check my decision to aim the pinion up and found some info that said if you are using a longer shackle that it also aims the pinion up (obviously) and the shim should be used to counteract that.

now i'm thinking i don't need the shim but i'm not sure.

My set up is 4.5" springs, 1.5" shackle, 231 transfer case no drop, dirtbound hack and tap sye and using a front drive shaft. and currently have the 6* shims aiming the pinion up.

There is no guess work here, you simply measure and buy an appropriate shimm.
At ride heigh position the rear axle yoke so it is vertical. Place a socket on the u-joint cap and use that socket as a flat surface for your angle finder reading.
Then take a measurement off the body of the driveshaft. With leaf springs you want the yoke to be 1-2 degrees less than the driveshaft. Compare the measurements and install an appropriate shimm.

Wow I did not know this, thank you! Everything ive read seemed like there was a golden rule type thing. Thank you once again sir.

jonzer12 said:

There is no guess work here, you simply measure and buy an appropriate shimm.
At ride heigh position the rear axle yoke so it is vertical. Place a socket on the u-joint cap and use that socket as a flat surface for your angle finder reading.
Then take a measurement off the body of the driveshaft. With leaf springs you want the yoke to be 1-2 degrees less than the driveshaft. Compare the measurements and install an appropriate shimm.

Click to expand...

x2.

Lift then measure for driveshaft modifications. Every jeep is different.