Well, I've been battling these vibes for over a year now...

I've got a 3.5" (4.5") RE full leaf pack in the back. I've also got a Iron Rock Offroad SYE with a modified front DS installed in the rear. I've gone from 2 to 4 to finally, yesterday I installed 6* shims on the axle. The 6* shims have produced the fewest vibes so far.



This is how it looks right now. Have maybe 1 to 2* difference in angles.

Frustrating thing is that the vibes are still there. I even pulled the rear and slapped the front on just to check if it was the DS (The one in the pic is the front, the rear has been cut down a little).

Anyone know what might be causing these vibes at this point? They are the worst at 30mph and come back from 45 on. If I let off the gas, they go away completely. Could it be the U-Joints in the DS? The U-Joint on the shortened shaft is about a year old, but I've ran it with the DS on with the 2 and 4* shims, so could that have caused the U-Joint to wear funny?

 

Did you actually measure the angles? A 10 dollar angle finder and the correct shims will be a whole lot more successful than just trying to eyeball it and throw on different degree shims until you think it's right.

Wouldn't hurt to change the U-joints... all of them.
Was the driveshaft balanced after it was cut down?

 

Yeah, it was balanced after it was cut down.

Not sure what other angles I could go to after this.

 

get rid of that front shaft. they have alot of play and i would not use that on the rear. id get a tried and trued tom woods like i run or have a local shop make ya one.

 

Where's the play at? The shortened front shaft has a V-8 rear yoke on it at the slip joint/U-joint. The Double Cardan Joint is still stock though. Think If I had that rebuilt it would clear up?

 

I ran a front shaft for years without any problems or vibes.

X2 on on the joints. That's a DIY job.

 

im goin to be doing a 4.5 lift in my 90 xj now i can use the stocke rear DS? im also getting a SYE but will i need to shim or are they all dif?

 

You can't use a stock rear driveshaft. The slip yoke eliminator eliminates the slip yoke at the tcase, and therefore you need a driveshaft with a slip-thingy on the driveshaft itself. Either junkyard a front driveshaft (from an auto trans) or shell out a bunch of cash for a tom woods. You need the double cardan CV type shaft after installing an SYE.

 

Like I said before, make the very minimal investment on an angle finder. Take the shims out and measure your driveline angles and do it right, instead of just throwing estimates at it.

If you've been fighting vibes for a year, they can't be that bad.

 

can you take apic from further back so we can see the hole shaft from transfercase to rear axle all together

 

hey i have the same problem, i just installed and IRO 5.5" inch lift and did a ROUGH TRAIL SYE by CROWN AUTO. by they book and a little help from pics on here but everything went good no binding, then i shelled out the money for a TOM WOODS CV Shaft .. and right around 30 mph the whole jeep vibrates!! I do not have it shimmed yet, but i was under the impression that the SYE " eliminated" driveline vibes... what should i do?

 

Is your rear axle yoke pointing directly at the t-case output? If not, that may be your problem.

 

i know the angle isnt perfect but its not horrible, it was worse before the SYE, now its not bad, i have 4* shims should i put them in?

 

There is no way for any of us reading this or any post to say what is the correct degree shim to use for any bodys Jeep. Spend $19 on an angle finder and MEASURE. XJs require shims from 0-8 degres when seting up a SYE. If you like spend $40 over and over go ahead and just try every size shim available. Or you can MEASURE and do the job 1 time.

BEFORE you start make sure the Bearings, U-joints and trans mount are good, axle shafts not bent, tires ballanced, make sure the vibe is NOT the front drive shaft. Make sure your shaft didnt throw off a ballancing weight.

 

dz1080-Have you found a fix yet? I also just installed a IRO HNT kit and have the same vibes. The provided yoke was too long (3/4"-1"), so I cut it down with a grinder wheel. Now, I looked at the instructional sheet for the 10th time and see they provided 5ea 3/8" washers. Maybe they wanted me to use those to "fill the gap" between the bushing on the t-case yoke and the newly cut t-case shaft? It's not in the instructions.