Rear Pinion Angle and Shims

Dawnpatrol

Jesse Higgins
Joined
Apr 25, 2016
Location
Raleigh
I recently installed a SYE and waggy springs (SUA) on my YJ. Now I'm thinking I need to dial in my pinion angle due to the new SYE. From a visual standpoint it looks like the 8.8 pinion is pointing just slightly below the t-case output. I took measurements of the drive line angles the best I could with a cheap angle finder and got the following:

Driveshaft angle: 23 degrees
Pinion angle: 13 degrees (measured on the 8.8 housing webbing)

Based on this it sounds like I would need an 8 degree shim to allow for the 2-3 degrees difference in angles. But then I had the thought that once you start changing the pinion angle, wouldn't it also affect the driveshaft angle at the same time and therefore require a smaller shim?

Side note: it drives down the road without any vibes the way it is now.
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Its not that complicated, referring to the waning degrees. You are also running the cv so you have room for error. idealy you want the pinion to be 2-3 degrees below pointing straight at the tcase. you dont look that far off from that. subtract the degrees from the pinion and the tcase output and see how that compares to the dshaft angle
 
I'd run what you have and see before changing anything. Maybe it's the angle of the photo but if it was me I'd got for a ride. It might be fine.
 
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Look how big those 8 shims are. To me it does look like it needs some shimming but not 8. I guess if you are not getting vibes then you might be ok. Adding shims properly is a PITA.
 
How soft are your rear springs? Throw a go pro on the frame and video it going down the road, see if it's torquing straight under normal cruising.. if it isn't aligned you may accelerate wear on the pinion bearings.
 
ckruzer said:
Its not that complicated, referring to the waning degrees. You are also running the cv so you have room for error. idealy you want the pinion to be 2-3 degrees below pointing straight at the tcase. you dont look that far off from that. subtract the degrees from the pinion and the tcase output and see how that compares to the dshaft angle
Click to expand...
I'll try and get the t-case angle this afternoon, but I thought for a CV rear you would want the pinion 2-3 degrees below the drive shaft, not the tcase output.
 
Tradarcher said:
dsc00006-jpg.490243


Look how big those 8 shims are. To me it does look like it needs some shimming but not 8. I guess if you are not getting vibes then you might be ok. Adding shims properly is a PITA.
Click to expand...

After seeing that picture the 8 degrees does look like way to much. I think your right in that its probably fine the way it is, however I had thought that the ujoint will last longer with less angle change a the pinion.
 
a_kelley said:
How soft are your rear springs? Throw a go pro on the frame and video it going down the road, see if it's torquing straight under normal cruising.. if it isn't aligned you may accelerate wear on the pinion bearings.
Click to expand...
sounds like a good reason to get a go pro
 
Dawnpatrol said:
I'll try and get the t-case angle this afternoon, but I thought for a CV rear you would want the pinion 2-3 degrees below the drive shaft, not the tcase output.
Click to expand...

i reread my words and they weren't the best for late night lol. your drive line should be zero. lets say if your pinion was dead on aiming at the tcase it was 35 degrees. a 32-33 degree dshaft angle would be optimal. Maybe 30 if you expect alot of settling with your leaf springs (if they are new).
 
Not vibrating you say? Run it, it's designed to run crooked...
 
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