Novak Conversions Jeep Wrangler YJ engine mounts

1992 YJ Pinion Angle

Sufa1992

Sufa1992

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May 7, 2025
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Hello everyone,

After raising my YJ about 2.5in with leaf spring shackles I started to feel vibrations at low rpm.
After looking inline a bit I found that the pinion angle might have changes and can cause these vibrations.

I measured the pinion angle with my phone (that’s what I have at the moment) and found it is at 16 degree angle, the drive shaft is at 7 degrees.

Should I get a leaf spring shim to fix that angle? If so, what will be the correct size to use?
Attaching pictures as well.

Thank you very much in advance!
 
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IMG_8970.jpeg
 
Generally speaking the killer is having 2 different end angles. Pinion to DS looks way more then your T case to DS angle. It looks like your diff end is rolled up. 1.5 degrees difference between either end is said to OK but more and vibes startin. Do you have the shims in now? I cant tell. Honestly after 15 jeeps for whatever reason one can be one way the another different when setting things up.
 
Gilaguy23 said:
Generally speaking the killer is having 2 different end angles. Pinion to DS looks way more then your T case to DS angle. It looks like your diff end is rolled up. 1.5 degrees difference between either end is said to OK but more and vibes startin. Do you have the shims in now? I cant tell. Honestly after 15 jeeps for whatever reason one can be one way the another different when setting things up.
Click to expand...

There are no shims installed at the moment.
I want to order some, but can’t figure out which size I should order.
If my pinion angle is at 16 degrees and my DS is at 7 degrees, should I get a 4 degree shim?
 
There has to be shims installed if your pinion angle changed when you installed the springs. Stock pinion angle is around 9-10 degrees. You probably have a 6° shim installed without realizing it. Look closer and if there are shims, remove them and recheck. You may end up needing a 2° shim or so but what you’ve got currently is way too much.


Edit:
I forget that you have that special weird axle….but regardless if you were stock height before and if the pinion angle was still 16°, how in the world did that not vibrate? If you truly do not have any shims installed currently, then I think you will need to buy shims, flip them backwards and let that angle the pinion down. You’ll want to measure the t-case output downward angle and shim the axle down until it about matches that of the t-case.
 
machoheadgames said:
There has to be shims installed if your pinion angle changed when you installed the springs. Stock pinion angle is around 9-10 degrees. You probably have a 6° shim installed without realizing it. Look closer and if there are shims, remove them and recheck. You may end up needing a 2° shim or so but what you’ve got currently is way too much.


Edit:
I forget that you have that special weird axle….but regardless if you were stock height before and if the pinion angle was still 16°, how in the world did that not vibrate? If you truly do not have any shims installed currently, then I think you will need to buy shims, flip them backwards and let that angle the pinion down. You’ll want to measure the t-case output downward angle and shim the axle down until it about matches that of the t-case.
Click to expand...

Honestly I didn’t check the pinion angle before installing the lifted shackles…
But there were no vibrations before the lift so I’m guessing something changed there.

I think I’ll order a set of 2 degree and a 4 degree shims just to be on the safe side.
 
Sufa1992 said:
Honestly I didn’t check the pinion angle before installing the lifted shackles…
But there were no vibrations before the lift so I’m guessing something changed there.

I think I’ll order a set of 2 degree and a 4 degree shims just to be on the safe side.
Click to expand...

I totally missed that you said shackles. I thought you did a 2.5" spring lift. In that case, yeah the shackles definitely rotate the pinion, I forget how much but it's probably a degree or two per inch of shackle change.

If you intend on keeping the shackles, I would just measure the t-case and compare it to the 16 degrees, get whatever shim brings the 16 back down to being close to the t-case output.

Stock t-case output is about 5 degrees down in my experience, but I haven't compared to other people's Jeeps to make sure mine is 100% correct.
 
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Tom Woods driveshaft website has a calculator for shims that will tell you the correct shim and you can order them there. You can also call them and they will help you with it.
 
machoheadgames said:
I totally missed that you said shackles. I thought you did a 2.5" spring lift. In that case, yeah the shackles definitely rotate the pinion, I forget how much but it's probably a degree or two per inch of shackle change.

If you intend on keeping the shackles, I would just measure the t-case and compare it to the 16 degrees, get whatever shim brings the 16 back down to being close to the t-case output.

Stock t-case output is about 5 degrees down in my experience, but I haven't compared to other people's Jeeps to make sure mine is 100% correct.
Click to expand...

So I finally got the shims and when I wanted to install them I noticed that there are already factory shims on the leaf springs…

I removed them and the axle is now 8-9 degrees.
I took it for a ride it feels so much smoother, no vibrations at all!
Amazing how removing these small shims made such a difference.
 
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Sufa1992 said:
Hello everyone,

After raising my YJ about 2.5in with leaf spring shackles I started to feel vibrations at low rpm.
After looking inline a bit I found that the pinion angle might have changes and can cause these vibrations.

I measured the pinion angle with my phone (that’s what I have at the moment) and found it is at 16 degree angle, the drive shaft is at 7 degrees.

Should I get a leaf spring shim to fix that angle? If so, what will be the correct size to use?
Attaching pictures as well.

Thank you very much in advance!
Click to expand...

7 to 11 degrees is what I’ve been told. I’m currently at 9degrees & have no problems. I’m running a 4inch lift & 35s with a Chevy 350/350 trans & 8.8 rearend.
 
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