First, yes i have searched and did find a perfect answer.

Its a 1993 XJ with 243xxx miles. I recently installed a Rustys 3in lift. Since then it has a new vibration.

When taking off from a stop, a shudder/vibration starts as soon as i hit 25mph, stays till 35mph and then slowly fades out at around 40mph. I can feel it in my seat and floor and hear it rattle my center console. Other then that, there are no more NEW vibrations since the lift all the way up to 85mph.

I pulled the rear drive-shaft. The u-joints feel to be in good shape with no play. The slip yolk splines looks to be in great shape.

I did install a 1" transfer case drop.
side note
immediately after i got done installing the lift and before i had the tcase drop on, i tried driving it around and it made a clunking ticking noise.

Another thing to note is i had previously thought my motor mounts were bad because my engine would move forward and hit the fan shroud under heavy torque. It no longer seems to do this latley.

What do you guys think?
*Bad U-joints?
*Needs a slip yolk eliminator?
*Bad motor mounts?

 

could be trans mount u joints maybe part of the problem that could also help a sye would cure the problem you might want to try the others first i have the same issues i just put a rustys lift on my xj my trans mount was bad and I'm goin to change the u joint with the new drive shaft angle.if i can I'm tring to avoid the sye because of cost. the vibe might go away with the other fix and once the lift settles,not sure about your lift but my rear is about a 1 inch higher in the rear.The best fix is going to be the sye good luck.

 

yea, i have had the lift on for about 2 months now and it has settled, but the rear is still higher than the front.
I just cant bring myself to spend time replacing the u joints, because they don't any different than new ones.
Trans mount was something i never considered.

 

Well, i just got done Replacing the u-joints on the rear shaft.
Its kinda hard to tell, but i think its still having the issue, only it seems to be less noticeable. What do you guys think?

 

when you changed the u joints you got better check the trans and motor mounts do you have a side shot of you jeep please post

 

just got home after driving it. Idk. it might be a bit better then it was but its still annoying.

 

I would do a SYE, when I had my Rough Country 3" lift i had vibrations, put i didn't address it until i put my new rubicon express lift in. I installed a SYE and some shims for the rear axle, and all the vibrations are now gone.

 

The more i think about it, the less i think the motor and trans mounts are the issue, since it has to do with speed and not rpms or load on the engine.

As for the sye is was eyeing this http://www.performanceoffroadcenter....roducts_id=153

Is this what i want? id like to just be able to put a stock front shaft on the rear to keep things simple.

 

I just took the jeep for a drive, withOUT its rear drive shaft.
While driving it in front wheel drive, the vibration is GONE.
So i see this as it needs a SYE.
Hows this: http://www.performanceoffroadcenter....roducts_id=153

and i want to run a front shaft in the rear.
Is this what i want? Cheaper anywhere else?

 

I had a similar problem at 50-55 mph and guess what? It was my tires. I bought brand new ones...no more extreme wobble.

 

I put "new" (5000 miles used) tires on my rig at the same time as the lift and it ended up adding some serious vibes. Turns out they're cupped/feathered and that's creating most of my vibes. If you have another set of tires you can throw on as a test that'll tell you for sure if it's the tires or not.

I thought my problem was U-joints or driveline vibes, but after really taking a look at my tires I don't think it is. The vibes come and go at different speeds for me too, so I'd say check the rubber!

GL

** EDIT**

Wow, note to self, read entire thread more carefully before posting suggestions. Hope you find a driveshaft to run. I'd be curious to know if you can run a CV driveshaft on the rear without a SYE...don't see why not.

 

Same tires that had no issues before the lift.
Also tried another set.

 

Have you checked the front wheel barrings? I had a similar issue, which was resolved by finding a bum passenger wheel barring. Replaced at the shop, baby runs like a top.

 

I'm going to go out on a limb here and say you need an SYE. Or your rear ds isn't balanced. If the angles are right on the rear ds and when you take it out, your vibes are gone, it probably needs balancing. When you replaced the ujoints did you put the yoke back on exactly where it came off?

Here is an explanation on what the angles should be:
http://www.4xshaft.com/driveline101.html

 

With a slip yoke, the slip is at the tcase. With a cv ds, the slip is in the ds itself.
Also a cv ds needs a yoke on the tcase to bolt to. Which is where the slip yoke eliminator comes into play...



The top two are CV shafts, the bottom two are the factory rears with slip yokes.