Odd noise after I installed lift

Since i installed new 3" springs last weekend, I've been having an odd noise coming from the trans/TC/Rear driveshaft area.

It happens when I let off the gas, as the rpm's drop, and when I am headed down a hill with just a light bit of throttle. Basically when the jeep is coasting, and the engine isn't really doing any work.

It doesn't make the noise when under load, or when traveling at a constant speed, as long as its past about 1/4 throttle.

The noise, is hard to describe, its a random sound, somewhat of a rattling/clunking sound. The best way i can describe it is if you took a box of some sort, put something moderately heavy in it, and shook it around.

I didn't install a SYE w/ the lift, Is this noise vibes from the driveshaft? I thought that driveshaft vibes usually happened when traveling at a certain speed, which this is not.

I wasn't sure if this should be in Modified or OEM tech because the stuff thats making the noise is something OEM, not something i've replaced. Move it if necessary.

I haven't had this problem with an XJ, but I have had it in a few other vehicles. It could be the Vibes, but it could also be a U-joint that was a little on the tired side, and the angle is compoundint the problem. It could just need a u-joint or some grease.
Its a place to start
-Steve

If the u-joint was bad, it would have some play in it, correct? I got under there and tried to move it around, and nothin.

as far as grease, where?

when i put my 4.5" lift on i had the same thing happen, only while braking hard, not any other time. heard a clunking sound when i'd hit the brakes or go downhill. turned out all i needed to do was add the 1" tc drop. fixed my problem

Both of the above are somewhat related solutions to the same problem (IMHO), but they both relate to u-joint angle. The new noise you hear is probably due to the u-joint having to flex at an angle that it is not used to being in. Replace your u-jpint crosses and see if that doesn't exorcise your noise. If it does not then you may need the SYE or a T/C drop to finally solve your noise problem.

My 97 with 3" and without t-case drop would make a noise as you describe.
I agree with the u-joint possibly being bad or out of sync with the rear. Get an angle finder to locate what angles your driveshafts and pinions are at. Mine would make a rattle/clunk noise right at the (what I thought to be) the t-case shifter linkage. Once I installed the t-case drop, the noises subsided. Yours being an 01, it might be the low pinion front axle making the noise instead of the rear. Sounds like a torque noise, make sure that your front pinion is still pointing towards the t-case and that your rear driveshaft slip yoke isn't pulled too far from the t-case.

Every XJ I have lifted has had this same noise when letting off of the gas. It has something to do with the slip yoke rattling or vibrating on the output shaft of the T-case. I have tried new U-joints, new slip yokes, and even some really thick grease inside the slip yoke(the grease does make it less noticeable but it comes back).

I have had to do a SYE to end the noise in each case.

I would go the least expensive route 1st. Drop yur t-case and throw in some new greasable ujoints. i would think this will solve yur problem. If you try to go any higher definately look into the SYE.

I had 3 1/2" lift with no issues. Spacer'd and shackled for 1 more inch and got the vibes. Dropped the tcase and all issues gone.

Best place to get a T-case drop?

My T case drop came with the kit from Rusty's. I've sure you can find one closer to your home or make your own.

you can't see any play in the rear driveshaft u-joint unless you jack it up the rear and then move the DS by hand with it on the ground everything will seem tight

01_XJ said:

Best place to get a T-case drop?

Click to expand...

I'd recommend Skyjacker since you have a newer XJ. The studs are sometimes welded in on newer models, and the Skyjacker allows an easy fix. If you get the Rusty's and 2 of your studs are welded in (my '98 was, and a friends '99 was), you're out of luck... I just didn't trust 2 bolts to hold up my crossmember!

Ordered my Skyjacker t-case drop from Quadratec.

JM2CW.
Michael

My lift also makes this noise, but I've recently paid a guy for his SYE and longer DS. Should fix the problems

jmowens said:

I'd recommend Skyjacker since you have a newer XJ. The studs are sometimes welded in on newer models, and the Skyjacker allows an easy fix. If you get the Rusty's and 2 of your studs are welded in (my '98 was, and a friends '99 was), you're out of luck... I just didn't trust 2 bolts to hold up my crossmember!

Ordered my Skyjacker t-case drop from Quadratec.

JM2CW.
Michael

Click to expand...

Wish I had known that before I had to drill a new damn hole in my frame rail to get the one stud that was welded in off.

It sounds to me to be the driveline angle. When you accelerate/under load your pinion moves up decreasing the u-joint angles BUT on deceleration your pinion moves back down increasing the angles stressing the u-joints. You NEED a t/c drop or sye. New u-joints might be in order as well!