i'm going crazy!

I bought a shackle lift kit with spacers for the front. For the back, the kit only came with a 1.5" extended shackle and then 1/2" leaf spacers. I decided to not use the rear spacers and just went with the 1.5" shackle extensions out back and 2" spacers up front.

The vibration is so bad, my rearview mirror vibrates, my side mirrors vibrate, and so does my dash!

It sits very level (even with the 2" spacers in front and 1.5" extensions out back plus new OEM leafs).

I was told that on an XJ, I'd only need to worry about driveline angles if the lift is over 3" or so. I only have MAYBE 2" of lift in the rear and front. What gives?!!

The thing that bothers the hell outta me, though, is the rear differential. Isn't it supposed to be parallel (or close to) the t-case? Mine is angled upward toward the t-case. My frame rails were angled at 4-deg, the pinion angle was 12-deg, the driveshaft was 16-deg, and the t-case output was -1-deg.

Would an SYE and longer driveshaft alleviate anything? Or is it the differential angled upward that is screwing it up? Or both? The vibe happens between 20-39mph and disappears any higher than that.

*crying* Help me. Ok, so I'm not really crying, but more contemplating a genocidal rage.

Thanks for any help.

what year is it? my 00 vibrates with 4" of lift because the slip yoke is at the end of it's travel. from 96 up they all came with the longer slip yoke, pre96 didn't, that could be it. It could also be from worn steering components that weren't noticed until the lift, it could be a whole bunch of stuff. I'd start with changing your DS angle. Make the pinion angle down 1-2* from the driveshaft. Assuming you've checked everything else and it's just not worn parts in need of replacing

whitneyj said:

Make the pinion angle down 1-2* from the driveshaft.

Click to expand...

That is the correct set up for a cv shaft not a stock slip yoke style

Replace your U joints, that would be the first place, then check your track bar and alingment.

you hvae driveline vibes. first replace your u-joints. a worn u joint will only get more noticable when you increase driveline angles and change the pinon angle. most driveline shops will install u joints for 15-25$ each with spicer joints, so under 50$ easy. or do em yourself. when they say 3" they usually mean add a leafs or full packs. leafs will still point your pinion up, but not as much as a shackle lift, especially a 1.5" lift shackle on a stock spring pack. remember, your t case output angle needs to be the same as your pinion. you can drop the t case to let the t-case output shaft angle to be closer to the angle of the pinion, but this puts added stress on the tranny mount, motor mounts, and also hangs down the tcase an extra inch, but it is inexpensive and can usually work in the short term until you can afford a sye. you also can shim the leafs, in your case fat part forward. you could try a yj slipyoke as well, your driveline shop should have them in stock for about 50$ and would install it for free with new u joints since they would have to take the old yoke off anyway. also check your front driveshaft pinion u joint, it might be bad as well, causing vibes.

Yeah your pinion is going to point up now, all you effectively did was push the rear of the spring farther away from the frame while keeping the front mount fixed, therefore you get a steeper angle across the entire spring. Shimming the axle a bit to get pinion output and trans output on parallel planes should make it right.

I did a 2" shackle/coil spacer lift on my '99 and had the same problem with vibes. The shackle raised my pinion angle so much that it took a 1" transfer case drop AND 6 degree shims to get the angles back where they needed to be. Even with that I still had vibes from 35-45 mph and over 70 mph. That was after replacing the u-joints as well.

Finally I broke down and did a SYE - problem solved. No more vibes. I hate to tell ya that, but a SYE may be the only way you're going to get rid of those vibes...

It's a '99 with the ChryCo 8.25" axle.

I replaced the u-joints about 3 weeks ago before I did the lift so they're still new. I had the vibe before, but not nearly as bad.

To jawa2021, did you retain the shims after you did the SYE? This is probably going to sound terrible, but are shims something you can just pick up from the autostore? Or should I go to a 4x4 shop?

I figured I was going to be doing the SYE, and the kit I was going to go for was the JB Conversions super shorty kit for $300. Any thoughts? Also, does anyone have any recommendations on a good driveshaft shop in So-Cal? I live in Orange County.

Thanks again, maybe it'll be a lesser genocide now.

When i did my budget lift, my shocks were close to being maxed out so it was a VERY ruff ride. Even with droping the tire pressure and every thing else every bump was felt. you may want to check those out...

The kit I got also included shock mount extenders so that's not a big problem either.

So you had mild vibes before the lift, changed the DS u-joints and lifted it, and now the vibes are worse? Did you inspect the driveline itself? I would check to see if it's dented or bent, that would throw it out of round and cause vibes. If you've dragged it over rocks or logs at all that's a distinct possibility.