Ok, so I put my 2" rocky road lift in about 1.5 weeks ago. I had some vibs between 30-40. they are still there today but they seam to come and go if that makes sense? always at low speeds. seems like when my vehicle is cold they are not there but after things warm up they are back.so I was going to do the t-case drop when I started reading people say it was a short term fix
and to wait that my u-joints would "wear in" could somebody explain to me the advantages and disadvantages of a t-case drop.is it a short term fix or can I use it for my DD for years without problems?

 

I would make sure that the vibes are caused by the lift and not worn parts. I am willing to bet that once you fix your vibe problem you wont need the t-case drop

 

so any suggestions as to what would be causing the vibes?

 

If it only happens at certain speeds try replacing u-joints and rotataing and balancing tires.


Then do a thorough vehicle suspension inspection. If ball joints have play ... replace... if unit bearing is worn replace... It literally could be one thing or a combination of several things.

I am willing to bet, an alignment and new u-joints as well as a tire roatation and balance will fix your problem

 

sorry i should have mentioned that at the time the lift went in I replaced all ball joints (upper and lower) u-joint at the wheel, all tie rods(not sure of all of there names) and tie rod ends. I did not have the vibes before lift and now I do.

 

Could be front DS. I believe it's got a cardon joint which, unlike the u joint, cannot be replaced. Instead hit the JY for one. Mine was like 90 bucks and had less mileage than the one it was going on. Can you twist your rear DS when in park? There should be no play. I've got a 2" BB and have no vibe issues. And as far as I know, you don't ever wanna do a TC drop, and you def don't need one at 2". Get the remaining joints checked and balance/rotate tires.

 

VT Jeep is wrong.. You can rebuild the CV part of the driveshaft, in fact napa carries the parts. I am willing to bet you need new u-joints in d/s.... could also be tires out of balance still

 

ok so I replaced all my u-joints (old ones were tight and did not appear to be worn/bad)and it seems to have gotten a little worse. vibes at 30-40 and 50-60(never used to do this at 50-60) .I have not had the tires balance checked yet, that is next on my list of things to do. it did however fix something else, it always seemed like it would run the slack out of something when I first took off and kind of bang forward, and did the reverse when I stopped. that is now gone?
what is the disadvantages of a t-case drop?other that clearance. does it harm the tranny/motor at all?

 

What did your 2" lift come with for the rear lift? With the 97+ drive shafts being shorter then the older XJ's it can cause a vibes because your pinion angle is off just b bit. I would not do a t-case drop. I would shim the rear axle 8-13 degrees and buy buy vibes. I didn't know this until I put a small lift in my 99 and had the same issue. I never would have thought that 3" on a drive shaft would make such a difference but from my experience it dose. My rear u-joint in my rear drive shaft went out while driving down the highway. lol It was fun. Also make sure when you check u-joints to have the tires off the ground. Not sure if you know or not but a bad u-joint can still seam ok when it has presser on it.

 

Rear lift came with shackles and shock extenders.
Well I broke down and did the t-case drop last night and the vibes were gone instantly.I ran out of money and time. I would like to take it out at some point and find out what the true cause was. Could someone explain the shimming of the rear axle?
also when I did u joints I only did the rear drive shaft, is it possible that i need to do the front as well (I think it is called the cv shaft?) it appears that there are three u-joints in that?