Differential pinion angle shims... (1 Viewer)

[Squidfisher]

I installed 4 degree pinion angle correction shims under the rear axle due to the lift and longer shackles and now there isn't room between the top of the leaf spring and the shock mount stud to get the shock installed.
If I lift the axle off the spring I can install the shock and re-install the axle but would have to remove the leaf springs of u-bolts and lift the axle to replace the shocks in the future.
What to do, what to do???

 

[CondeCruiser]

Need pics

 

[pb4ugo]

4* is pretty extreme. Did you measure the driveline and pinion angle to confirm it requires 4*?

 

[rockcod]

If you can get the shocks to mount the way you described, great, but how often are you going to be changing shocks? Is it worth the worry? I would be more concerned about the driveline vibration caused by not having offsetting u-joint angles.

 

[Squidfisher]

4* is pretty extreme. Did you measure the driveline and pinion angle to confirm it requires 4*?

No, which is likely a serious mistake. When I got the beast it had 2 1/2" Downey shackles ON THE FRONT for some reason. I replaced those with 1.5" shackles and moved the Downeys to the rear, which leveled the truck perfectly, as it was almost a Carolina rake before. It has 4" Skyjunker springs already, so I figured that with those and the long shackles the pinion angle would require correction, so I reviewed online lift/shackle length info and made the four degree decision. Could be wrong, for sure.

 

[Mark Jennings]

With 4” skyjackers and longer shackles, 4* is a good starting point. And if you were to measure (recommended), I bet you would add maybe 2* more. Thumb Rule: 2* every 2” of lift, plus another degree every 1” of shackle length over stock.

So until you measure, and decide on a final shim, keep an eye on drive shaft bolt tightness. Especially at the T-case.

 

[pb4ugo]

No, which is likely a serious mistake. When I got the beast it had 2 1/2" Downey shackles ON THE FRONT for some reason. I replaced those with 1.5" shackles and moved the Downeys to the rear, which leveled the truck perfectly, as it was almost a Carolina rake before. It has 4" Skyjunker springs already, so I figured that with those and the long shackles the pinion angle would require correction, so I reviewed online lift/shackle length info and made the four degree decision. Could be wrong, for sure.

You can buy a cheap angle finder at a hardware store. Measure with the vehicle on level ground. The driveline and pinion shaft should be parallel to each other. Guessing on the correction can cause a vibration and could be costly. Tom Woods website has a good tutorial on driveline and driveshaft angles. I run 4" Skyjackers and found a 2* shim could work in the rear, but would slightly over correct. My driveline has been modified though. I originally installed a 4* shim on the frt for caster correction which got me within spec, but 6 degree was better.

 

[77mustard40]

With 4” skyjackers and longer shackles, 4* is a good starting point. And if you were to measure (recommended), I bet you would add maybe 2* more. Thumb Rule: 2* every 2” of lift, plus another degree every 1” of shackle length over stock.

So until you measure, and decide on a final shim, keep an eye on drive shaft bolt tightness. Especially at the T-case.

With 4” Skyjackers in the rear my need for a shim went away, I previously needed a 2* shim when I had OME’s. IME Skyjackers are longer and the location of the center pin differed from my old springs, so when I measured the pinion and TC Output Flange angles I was only 1* out so no shim in the rear for me.

Everyone should measure their angles before buying and adding shims, yeah there are general rules but IME every truck is a little different. Waiting also let’s you figure out how long a replacement center pin you will need to run a shim.