Shimming Rear Axle for Pinion Alignment

[W_A_Watson_II]

OK, I had a 9º delta in the pinion and drive shaft after installing the SYE transfercase (measured twice). Drive shaft was at 13.5º and the pinion was at 4.5º. So based on reading other post and expecting some axle wrap and possibly adding slightly longer shackles, I decided to only rotate the pinion 6º leaving me a 3º misalignment.

I ordered and got the 6º shims, and finished the installation this morning. I remeasured the angles, and now I'm confused (yes I know that's easy to do to me). The drive shaft is at 10º and the pinion is now at 11º. So now the pinion is pointed up by 1º rather than the expected pointing down by 3º in respect to the drive shaft.

So the 6º shim effectively moved the pinion angle 10º? (yes I only installed one shim per side)

I know the use of the shim in a spring under also moves the axle up, in my case approx 1/4-3/8". Did this additional upward movement of the axle combined with the shim result in my now needing to get a lesser degree shim?

Any idea?

Will

[wdln]

I know the use of the shim in a spring under also moves the axle up, in my case approx 1/4-3/8". Did this additional upward movement of the axle combined with the shim result in my now needing to get a lesser degree shim?

It would be a lot of math and geometry to figure it out by the numbers, but I could see the thickness of the shim playing a role. Additionally, the point you are rotating the pinion around isn't the tip of the pinion but much further back at the axle tube, which means the tip of the pinion moves quite a bit even for a small rotational angle change. Plus, the driveshaft pivots at the back of the transfer case too. So as you pivot the axle up and raise the tip of the pinion, you're changing not only the angle of the driveshaft at the pinion but also pivoting the front end of the shaft up slightly, which would contribute to the angle at both the front and back end of the driveshaft changing even more.

Confusing to say the least, but I think that might be where your bigger-than-anticipated change is coming from.

[W_A_Watson_II]

Yep, the upward movement of the Yoke (in my case approximately 1-2/3") is indeed the culprit. Looks like based on some geometry I can get away with 4º shims, and they will yield a 2º delta in the correct direction. Then if I add the 1" longer shackles (1/2" lift, but will only result in 1/4" lift with 4º shims) I will end up with approximately a 1.5º angle between the yoke and drive shaft.

The image on the left is "stock", and the one on the right is with the 6º shims.
(left circle is the axle tube, center circle is the yoke, the left line is the drive shaft)

[W_A_Watson_II]

Connected the Heater Hoses, Installed the Wipers. I also installed the front fender flares, and then the front Fenders. WOW, are these fenders difficult and challenging to attach. I also attached the guard for the air filter. I tried to apply the "Jeep" Decals I ordered, but they were in no way the proper font/design. Guess I'll have to order a set from a better supplier. Next I need to order the front side lights, so I'm legal and mount the MP3 Amp in/under the dash. I've probably got 460 hours into the Jeep over the last 5 months, with 60% of the time in Body Work and Paint. A lot of fun and learning.



As Purchased:


Start of the Job:


As it sets this evening:


http://www.jeepforum.com/forum/f12/star ... st14094522
http://jeep.wawii.com/93YJ_TrannyJob.htm

Will

[Duke Winch]

I tried to apply the "Jeep" Decals I ordered, but they were in no way the proper font/design. Guess I'll have to order a set from a better supplier.

If your referring to the JOOP stickers ... on a TJ the factory stickers don't even come close to matching the raises JOOP in the sheet metal. You center them the best you can. I imagine a YJ is the same way.

Are you still planning on installing rock rails?

[W_A_Watson_II]

The "J" on the side's were the worse fit there, but the "e" on the CJ Tailgate was so bat it would never look right.

Yea, I need to build a set still. Since I still plan on eventually doing my own Tube Fenders and rear flares, the Rock Rails for now will be less sophisticated, just to provide some protection, and a step for the girls to get into the Jeep with.

Will