SYE - Drive shaft - Angle measure

Installed the SYE (Advanced Adapters on a NP231J) last weekend. I know I need axle shims under the leafs.

Just want to make sure I have this measure thing down correct. Yes, I've read, and seen how other people do it, but it seems like everyone has their own way of doing it, so I'm just double checking myself to see if anyone catches a flaw in what I've done.

1st measurement - Angle of Drive Shaft. ~17-18*

2nd measurement - Flat portion on the side of the tail housing on C8.25 diff. - 8-9* (This spot appears to be parallel with the yoke, so I figured it would be easy to measure there)

3rd measurement (more to check myself?) - face of yoke on C8.25 - (drive shaft was already installed, so I just aligned it with the face based on eye ball) This appears to be about 92-93*. From what I've read - subtract 90 degrees to get the degree of the output on the Diff. 2-3*? - This doesn't seem right, I'm sort of throwing this number out.

If I assume 1 and 2 are done correctly, I'm about 8-9* out, and if you subtract 2* because you want to be under 2* when not under load, I should need a 6* shim. - Any other measurements seems like I need a MUCH larger shim, which does not seem to be typical with the lift that I have. (most people say 1* per 1" of lift "typical".....is anything ever really typical on an XJ?)

OME 3.5" lift springs in the back, I did not install them, so I'm not sure if this is netting more than 3.5" because I don't know what the original height was. I've read it was 17" from center of axle to start of fender, and I'm more like 21" so I'd say its safe to assume I have about a 4" lift.

Drive shaft by Titocci, on Flickr
1st Measurement

Diff - Output by Titocci, on Flickr
2nd Measurement

Yoke Flange by Titocci, on Flickr
3rd Measurement

At 4" a six degree shim seems about right, you can also put the angle meter on the flat part to the left/right of the cover.

In the 2.5-3" range I am using a 4 degree shim.

The fat part of the shim goes towards the rear to roll the pinion up. Note that this also lowers the fill plug hole so when changing the fluid you need to make sure you get enough in.

Euology101 said:

2nd measurement - Flat portion on the side of the tail housing on C8.25 diff. - 8-9* (This spot appears to be parallel with the yoke, so I figured it would be easy to measure there)

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Always measure from a machined surface.

I am at 5.5" of lift and have 4* shims.

Tim_MN said:

Always measure from a machined surface.

I am at 5.5" of lift and have 4* shims.

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Yeah, I find that just as many people above 5" of lift, are using 4* of shim, but I'm also finding others who are in my boat with 3.5"-4" of lift, needing 6*. I chalk it up to "there is no such thing as typical".

Is there a machine surface on the 8.25 that I should be measuring off of? I tried the yoke flange, but that seemed to give me a weird reading of 92* (or 2* when you subtract 90) Is there another machined surface that we know is parallel or exactly perpendicular to the yoke?

Same lift (4" exact), same axle (8.25), and I'm chasing vibes.
I'm running 4* shims with vibes currently above 65 mph. I'm taking my shaft to get balanced, since I just rebuilt it. I might have to use the 6* shims. My driveshaft is at a 14* angle, and the pinion (where you measured as well) is at a 12-13* angle; I should be okay. Still Vibes...

CarbonXJ said:

Same lift (4" exact), same axle (8.25), and I'm chasing vibes.
I'm running 4* shims with vibes currently above 65 mph. I'm taking my shaft to get balanced, since I just rebuilt it. I might have to use the 6* shims. My driveshaft is at a 14* angle, and the pinion (where you measured as well) is at a 12-13* angle; I should be okay. Still Vibes...

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I pulled my front drive shaft and rebuilt it, then took it to get balanced, I did all of this knowing I would use it as my rear DS until I ordered a new one. I plan on picking up another drive shaft next week, and putting the front one back in the front.

Sounds more like you just need a balance if you're within 2*. "Hopefully"

Euology101 said:

.... Is there another machined surface that we know is parallel or exactly perpendicular to the yoke?

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The pinion snout face for sure, and the probably the diff cover bolt surface are 90* to the pinion center line.

Tim_MN said:

The pinion snout face for sure, and the probably the diff cover bolt surface are 90* to the pinion center line.

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I just went outside and looked at this again, as MD21722 stated earlier, on the left and the right side of the cover, there are flat spots, which are on the same plane as the bolt cover. I measured at these spots, and found that I had 818. If you subtract 90* your looking at 9* as I came about earlier. Double checked the DS again, and that is 17-18*.

Quick Autocad sketch of everything including a correct length DS shows that if I start out with a 9* pinion angle, and correct it with a 6* shim, I'll end up 1.7* difference. (this is due to the angle change of the drive shaft when moving the pinion)

Should have the shims tomorrow, so I guess we will see what it feels like tomorrow night after I drop everything.

Stock shackles? Depending on the length extended shackles will give you a degree or 2, think that is were the difference is with some needing 4* vs 6*.

V-hunter said:

Stock shackles? Depending on the length extended shackles will give you a degree or 2, think that is were the difference is with some needing 4* vs 6*.

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You are correct, stock shackles, I never thought of that as being the reason I would need 6* but that makes sense.

I spent a few hours last night looking over everything. Shackle angle is vertical so I plan on picking up a set of No-Lift relocation brackets, and replacing the stock shackles.

When I get the proper shackle angle, theoretically, I should lose a slight amount of lift, and my pinion would go down (angle between pinion and DS would go up), since I would be pulling the springs both backwards, and arcing slightly upward, pointing the pinion more down. I think to counteract that a small lift shackle like 1/2" might keep me where I'm at. Does this sound correct?

Installed the shims this evening, and wow, what a difference. I bought the jeep already lifted, and they just did a TC drop.

Getting rid of the TC drop alleviated issues I was having with my Motor Mounts, and got rid of engine vibrations (even with Brown Dogs). Then installing the SYE, and correcting pinion angle got rid of the droning, and growling, and vibrating at both low and high speeds.

Measured angles again, and I have about 1-2* between the two, which is good, but I'm worried if I get HD shackles which lift, I may be over, and have to swap back to 4* shims.

Thanks for the help all!

I'm running a bastard pack made from the Crown HD pack with a S10 main added. With the HD no lift bracket and JKS shackles I ended up using a 4* shim. Even with the shackle in the top row of holes the rear spring eye is lower than stock so it tips the pinion up. Keeping the shackle angle the same and moving to the lower row gains me an inch of lift without throwing the angles out enough to need a different shim.