Can axle shims take the place of a CV driveshaft and/or SYE at say 3-4.5 inches of lift? Seems a lot cheaper to just do shims. What are the drawbacks to using them? Thanks

Yes. No Drawbacks. Your shim needs to be angled at 3.5 degrees for 4 inches of lift.

I know none of us can read minds, but why would anybody spend hundreds of dollars to do SYE and CV if all you need to do is add shims? I would think this also only works on the rear axle. Is that correct?

Well to get rid of all your vibes, you will need to do the axle shims and a TC cross member 1" drop. A lot of guys don't like to do the TC drop because they say it defeats the purpose of lifting your rig....which it does to an extent. I'm lifted 6" with 33s and a 1.25" TC drop and it hasn't limited my off road ability at all. Honestly though, I too, am currently putting together the parts to install a HB SYE on my XJ.

agreed, depends on the lift height.

shims are used to correct the pinion angle on your rear axle (or front). for a sye, the pinion needs to be pointed up, about 1 or 2 degrees below the driveshaft angle. If you run the stock slip yoke/driveshaft, your pinion should be pointed nearly straight forward, same as the output shaft on the transfercase. The slip on the stock shaft does not have much play in it. Flexing out could cause it to put pressure on your TC when it is extended out. Those seals can leak from this as well.

You are just better off getting an sye when you lift, also you are upping the strength of your output shaft if you get a HD one. Some allow you to run the same driveshaft front and rear, so you only need to carry 1 spare. Changing a U-joint is a lot easier with a SYE as well since it is easy to just unbolt the shaft.

no shims will not replace a SYE
yes you can use them but you need to remember to keep proper drive line geometry
so you cant just shim up the pinion arbitrarily yes it will fix binding but not harmonic vibrations witch some of you may not even know you have because of tire vibe masking it

will axle shims alone cure the vibes or does it have to be done along with a tc drop?

if you are still running the stock slip yoke you probably dont need shims. Just do it right the first time, or you will end up paying more in the end.

I have a 3.5" Rubicon Express lift on my XJ and am about to install a SYE and CV driveshaft. What angle shims do I need to put in the rear and what should the geometry be, pinion straight with shaft, or slightly below?

Thanks,
Tyler

pinion should be 1 to 2 deg less than the drive shaft

Thank you for the info. Does the shimming have to be done immediately after installing the CV driveshaft, or will it be ok at the stock pinion for a few weeks?

the sooner the better
the shims ar cheep and why not just do it while you have all the tools out for the SYE

I have one set of the RE shims, I believe they are 2.5 degrees, do you think they will do the trick, or will I need more for the 3.5" lift? I will also have to get new U-Bolts since they are torqued, correct? And one last question, you are awesome by the way, what is the proper torque amount for the rear U-Bolts on those Cherokees?

Thanks so much!

Tyler