just installed a 3" BB. took her for a test drive and felt the vibes. I lowered the transfer case skid plate roughly 3/4" to 1" and still got vibes. Any ideas that I can get rid off them? Looking for a cheap and easy fix.

Once you start modifying a Jeep, "cheap and easy" sometimes goes out the window.

First off, I am never in favor of lowering the t-case. That's a crappy easy response that partially defeats the purpose of a lift to start out with. It reduces certerline ground clearance. It changes the angle of the engine and oiling galleys, and a host of other possible things. Lowering the t-case itself can cause or aggravate vibrations if the t-case mounts or engine mounts are a litte worn.

The best way is to fix the driveline itself.

Fisrt off, I would carefully check the u-joints on the rear driveshaft for any looseness at all. Sometimes, one of the rear u-joints can be a litle loose, but we never notice it if the driveshaft is operating at OEM specs. Then, when we lift the vehicle, and run the driveshaft at the limit of or exceeding OEM specs, the loose u-joints manifest themselves as driveshaft vibration.

If the rear driveshaft has a regular u-joint at the front of it, then get it modified so that there is a CV joint on the front end. Then rotate the rear axle so that the driveshaft is pointing right at the output of the t-case, within 1 or 2 degrees. I have never seen that method fail to cure rear driveline vibrations.

There's no cheap way ksp. 1 inch riser motor mounts might help a little ($90). Next idea would be a double cardan style driveshaft for the rear. The best way would be to install a SYE kit with the slip yoke in the driveshaft ($500). <img src="/forums/images/graemlins/frown.gif" alt="" />

Good advice from both, but I'd start with checking the U-joints. IMHO a 3" lift should not give you vibration problems, esp not with a relatively new TJ. Next I'd be checking steering components and alignment unless I was sure it was caused by the drivetrain.

I don't understand what you mean by rotating the rear axle? And how does one go about modifying the drive shaft, is that this "SYE/CV" conversion I keep reading about everywhere? <img src="/forums/images/graemlins/confused.gif" alt="" />

I checked the U-joints and everything appears to be in good shape. Got the front end alignment as I planned, but the vibes are still there. She vibes when accelerating (and just slightly when I level off) so I am almost sure it's coming from the drive train, not the steering components.

Will these vibes cause any damage if I keep driving it right now? I am not planning on leaving it be, I want my Jeep to last and I want to do what I can right now to try and eliminate them, if they're gonna destroy something. But I do have to drive her 30+ miles to work every day, so leaving her parked until I figure this out is really not an option.

Do you think there's a good chance the 1" MML would get rid of it, or should I just save some $$ and do the SYE/CV conversion ASAP?

I doubt the vibrations will hurt anything unless you feel a real hammering effect....like it's hammering against the t-case, but I doubt that. I don't know what the MML will do for you. I think I got my CV/SYE set up for about $230 for the aprts. If it's drivetrain a CV set up should fix it. I'm still surprised 3" is causing that much problem.

Rotating the rear axle means to rotate the axle housing on its own axis, so that the shaft of the pinion gear is pointed more upward, toward the putput shaft of the transfer case.

In a vehicle with a leaf spring suspension, such as a CJ or a YJ, the rear axle is rotated by installing tapered shims between the springs and the spring pads on the axle housing.

In a vehicle with a linked suspension, such as a TJ, the rear axle is rotated by changing the relative length of the upper and lower control arms. However, unless either the upper arms or the lower arms are adjustable, that's not an option. Most "long arm" lift kits for vehicles such as the TJ contain adjustable upper control arms.

That's what I thought. It's bone stock, so I don't think this is an option. <img src="/forums/images/graemlins/frown.gif" alt="" />

Adjustable CA's will cost more than the CV/SYE. About $300 per pair IIRC. The MML sounds like what I would try first, even with a CV/SYE setup just to help get the angles back closer to stock.