Im at 4.5" with a sye kit installed. I checked my rear pinion angle cuz im getting some bad vibrations at speed and there is about a 4* degrees difference. I read the lifting the pinion decreases the driveshaft angle at the same time. So my question is would a 2* shim work? from what Ive read this seems to be the way to go.

 

if its 4 degrees off..get 4 degree shims.

 

but wont that put me past 0* degree?

 

If you have a double cardan drive shaft ( which you should) the the rear pinion should be pointing strait at the transfer case yoke. The actual shim degree could vary depending on lift components.

I'm at 4.5" lift and I have 4 deg shims and it's perfect.

 

I do have a double cardan shaft. How do I measure to fix what shim I need?

 

1) get an a magnetic inclinometer (angle meter)


2) park on level ground

3) attach inclinometer to driveshaft and note displayed angle

4) find a (hopefully flat) spot on your diff that allows you to attach the inclinometer to read the pinion angle. Note, base of the inclinometer MUST be parallel to the pinion, otherwise you may have to eyeball it.

5) take the two angles you got and do the math. The pinion angle should be set a little below parallel to the driveshaft to compensate for axle wrap under acceleration.

 

cdn xj, I did that, actually disconnected the DS at the diff to measure the pinion angle. DS was 14* and pinion was 80*, different orientations. SO its a 4* difference.

I read that when you shim the axle to the pinion angle you change the DS angle so you dont need the full 4*. Also I want room for axle wrap. How much axle wrap is there with leaf springs?

 

I have a 4.5 lift and used a 4 degree shim, I still have 2 degrees for axle wrap. I run OME light spring , so it depends what rate your rear springs are. If you don't hole shot your jeep you'll be ok.

 

I can't remember offhand what the acceptable range is, but I should think you would be ok with 4*. I think I'm running about 2* or so.

As for the vibes, are you sure it's the rear pinion and not your front? I had to live with driveline vibe for a while until i stopped being lazy and dealt with my front pinion angle. lol

Also, how are your u-joints? check all 6 to make sure they're not sloppy.

 

I made sure it wasnt the front, removed the front shaft for a week. The vibes decreased but didnt go away. I have a control arm drop kit in the mail for the front and will order shims for the rear today.

Anyone have issues with shims cracking? I was talking with a friend of a friend and he said he doesnt like shims cuz the crack. Only had ont real example of it and I cant see steel shims cracking.

 

I'm on a 3.5" RE superflex kit with full packs and preemptively bought 4° shims based on others' builds. They worked perfectly and are solid steel from RE.

 

Did you ever get rid of the vibration and if so, how?

 

None of those guys have been in the forum for quite a while. You may just have to keep searching and reading... and learning... and asking questions... plenty of info on this forum to figure out your problems. I am not lifted yet, so I cant help with your exact issue..

 

Thanks for your reply. I am actually NOT lifted either. I am going to attempt to restore the rear to completely stock. I have longer rear shackles, but I am going to start with putting back the stock ones.

The only other question I have is... do the front springs also wear out? Do I need to get new FRONT springs to make it level again...

I am getting shims also, incase I need to use those to fine tune.

My goal is to make this JEEP Cherokee STOCK HEIGHT, and make it a strong tow vehicle... NOT a rock climber, or a lifted JEEP for now.

Thank you!

 

be aware the Sports, (and some Limited) run 1" taller springs all round

If reverting to "stock" I would probably use them in any case

the best way to check is to get under and measure axle tube to frame rail heights, correct data is on this forum somewhere