Driveline/Slip Yoke Eliminator Questions...

[IdahoJeeper]

Hi all!

Bought my current 96 XJ late last summer. Have been going through it taking care of loose parts, making a few mods like the bored throttle body and spacer, hood vents, intake. Have the rear shock bar-pin thumping problem, JKS eliminators are on the way. When I bought it, it came with a Pro-Comp lift with lower control arms and front & rear springs. I'm guessing a 3" but not sure. In addition, the previous owner installed 2" coil spacers in the front and 2" lift blocks in the back. For tires 31X10.5 15".

From the first day there was a terrible vibe coming from the back. Right away I figured the rear was too high and I was getting driveline vibe. I watched my wife back it out of the garage one morning and saw how the rear springs flexed with those blocks in there and decided they were coming out. The rear looked too high anyway and with the blocks out it sits about level with the front. Now the only vibe coming from the rear is at start-up, say from 0 to 20 mph.

I have a t-case lowering kit and was planning on installing it, but had a couple questions before I limit my underside clearance:

1) with a slip yoke eliminator, a new driveline is required, how do I know the length and where would I find one?

2) can the same effect be acheived with a longer slip yoke driveline, or would the rear axle drive the slip yoke into too far the t-case under a heavy load?

3) Am I even thinking in the right direction? I already have a small wedge shim at the axle to turn the pinion up a bit, it seems like there's a lot of slip yoke showing at the t-case...

Any input appreciated, thanks!

[DwightRGV]

You may want to try the t-case lowering kit out first. It doesn't take too much time to do. If that reduces or eleminates the vib, then you know it is due to the drive line angle. At that point you need to decide if you want to do a slip yolk conversion and put the t-case back up. Their are lots of choices for drive shafts, a local shop or internet possibilities like Tom Woods Custom Drive Shafts (www.4xshaft.com). Normally you put in the slip yolk conversion, and measure for the new drive shaft (and wait a few days for the new shaft). It is really not too hard to do. You'll find measuring instructions on tom woods site. If the drive line still vibrates after lowering the t-case make sure to check if the current drive shaft is not out of balance (bent, dent, etc.).

[Ray H]

It sounds like you are sitting at about 4"+ in the back. You may be able to get rid of all the vibes by using a t-case drop but I doubt it.
The info above on SYEs and driveshafts is accurate. I would like to add a cheaper alternative. If you have an automatic transmission, you can use an XJ front driveshaft from another automatic and a Rubicon Express SYE (RE1807), a Spicer 211229X flange and a couple degree shims for about $200.

[IdahoJeeper]

Thanks guys! Both good info!

Ray, I'm intrigued by the front driveline idea... It is an auto, and I have my other wrecked 96 which is also an auto tranny... Is that front driveline beefy enough to turn into a rear? I assume from your suggestion that the length is correct...?

Very interesting...

[Ray H]

The length should be fine. People have been doing it for a few years now and no one I know of has complained. Unless you are planning to run 33" tires and lockers and so forth, I would think it would be plenty strong. Its a smaller diameter than the rear but I thinks its made of thicker stock.
Its eactly what Im going to do when I get my lift together. Ive actually got all the pieces in the garage, just waiting on a couple small things and time.

Go here,http://www.naxja.org/forum/forumdisplay.php?f=43 do a search for "front driveshaft" or something similar. Lots of good info on it.
You dont have to use the RE SYE with the front driveshaft. You can use others, it just depends on how much $$$ you want to spend.

[IdahoJeeper]

Coool!