Front end noise/vibration

I am not sure what to check and have when through alot of parts of this front end with no luck. It seems to only happen when at speeds over 35mph and becomes worse the faster you go. However this noise/vibration only happens when you lift up on the throttle, so long as you are on the gas pedal nothing...no noise/vibration. As soon as you lift to "coast" it happens...any ideas?

2000 XJ, AW4, 4.0, 5" lift, 33s

what kind of noise is it first of all?

Based only on what you've said, I'm not convinced it the front end at all. Since on the road, in 2wd, the front is "coasting" all the time, getting on and off of the gas makes little difference to the front. I'd be looking at the rear end...ring and pinon or pinon bearing. Those are the components that will change their "strain" when on or off the gas.

Just my $0.02.

check your drive lines when the pinon angle isnt quite right you can hear and feel vibration usaly when you let off the gas

Would suggest you check your driveshaft U joints.... They can cause driveline vibrations that can transfer in different directions and appear to come from somewheres else.... Depending upon how worn they are... you will feel vibrations either when you load (apply torque) or unload (remove torque).

I agree with Charles and windle, it sounds like a drive line vibration. I would check for bad U joints if there good, you may try a small T case drop, or a shim under the rear springs. Also if you don't have a SYE might be a good time to buy one. I have the same thing I only have about 4" of lift in the rear I am waiting to buy a T case with a SYE from the guy at work. By putting a D44 in and doing a t case drop I made my vibe a lot less.

Flyfisher said:

Based only on what you've said, I'm not convinced it the front end at all. Since on the road, in 2wd, the front is "coasting" all the time, getting on and off of the gas makes little difference to the front. I'd be looking at the rear end...ring and pinon or pinon bearing. Those are the components that will change their "strain" when on or off the gas.

Just my $0.02.

Click to expand...

I was originally worried about my front pinion angle being off and thinking it might be the source of the noise/vibration. So what your saying though is I wouldn't feel or hear this vibration from the front driveline so long as its in 2wd?

Also what is the best way to check ujoints? I have tried the old put it in neutral and twist the driveshafts and haven't found any play in them, is there another method?

I do not have an SYE yet and definitely have some vibrations coming from the back but was trying to figure out where this vibe is coming from in the front.