I've been fighting a driveline vibe for almost six months, now. My XJ is lifted 4.5" with a Rubicon Express hack/tap SYE, 6 degree shims, and a stock XJ front driveshaft for the rear.

Every single U joint in the Jeep has been replaced with moog or spicer. New motor mounts, new trans mount. The output yoke is torqued to spec and there is no play in the driveshaft system. It's completely sold when bolted in. The rear output yoke is exactly 2 degrees below my driveshaft angle.

The noise only happens on moderate to heavy acceleration. It gets really bad over 50mph and stops completely when I let off the throttle. It's a pulsing noise and gets more intense and frequent the closer my vehicle approaches a shift point. The vibration isn't extremely loud, but it's enough to annoy the hell out of me and shake my loose change.

The noise is not present if I pull my rear driveshaft. The shaft itself is not warped and spins true to its axis.

It just appeared out of nowhere one day, I had this driveline setup for a few months with no issues. Get in and drive one evening and instantly notice.

What could it be? What should be my next step? I'm completely stumped. To make matters worse, there are no professional 4 wheel/Jeep/off-road shops around that could assist me (indiana), so I'm ****ed there as well.

From my experience, that kind of noise/vibe is a u-joint going bad.

Could you have damaged one while putting them in ?

Are you sure the driveshaft end to end ?

Have you tried a different rear driveshaft to see if it is the shaft itself or not ? like maybe swap your front & rear driveshafts to see if ti changes or goes away ??

Gonna suggest, factory balancing weight gone missing off driveshaft? Would explain abrupt appearance of vibrations. Have had that before, didn't figure it out until i had the Ds in hand; could clearly see the broken tack weld.

This is a very good suggestion. All it takes is one little weight to fly off and its out of balance. Maybe it came loose when you were wheeling and it came off goin down the road at a later time.

What type of bushings in the leaf springs?

been there and done that and had it be driveshaft balance issue. Did you try using your other front DS and see if there is any difference?

I swapped my front and rear shafts with no success, but since my RE hack and tap SYE uses a different flange, I had to swap that as well.

I swapped driveshafts but it very well could be an issue. My spicer output yoke on the DS has very slight play. I can shake it back and forth and hear a very, VERY faint click. I'm going to get the part warrantied today. Hopefully that'll be an issue.


AFAIK just standard rubber, not poly. They are RCX leaf springs.

Swapped shafts with no improvement, however I also had to swap my output flange since the RE SYE uses a proprietary one. Since the flange is the common factor between the two shafts, I'm hoping the very small amount of lateral play in it is my issue here.

What condition are they in...if they are worn out, they can cause vibes as well. I think the previous poster was also getting at this as well as the material.

They are only a year old; perfect condition with no cracking. My shackle bushings are stock with 189k miles on them, however. They are dry and have some hairline cracks, but nothing serious.

Was lift installed then vibes appear . Can you post some pics.

Are you sure ??


On my 96 (w/160k on it, 40k on the shackle bushings), I thought the same thing, till I put in a SYE kit and when went to put in shims, I saw how bad the shackle bushings were....bolt was not even close to being centered in the bushing at all.

The lift and SYE were installed for a few months with zero vibes. Just appeared out of nowhere driving home one day.

the bolt is centered, and I can't see more than hairline cracks. Besides removing the shackle entirely (which I'm really not wanting to do), is there any other symptoms or indications of shot bushings?

you can have the shackle off in 5 minutes...i just did this morning haha!!! Went back on even faster

The SYE I used is from Iron Rock Off Road it uses a stock front drive shaft it doesn't use a flange it bolts up the same as it does on the front , so if you are out 4 wheeling all you need is one dive shaft for a spare . I think the flange could be the problem .