Front DS Noise after lift

At the start of the winter I tore down my old 89' Xj with a pretty sad unibody and did a 4wd conversion on my new 96' 2wd XJ with an amazing frame thanks to the Southern States.

Previous owner put a Rusty's 6.5" lift on the 2wd... ??

Long story short the 96' is now 4x4 thanks to the old girl donating her organs. Works well with the exception of some noise in the front drive shaft when 4x4 is engaged, hi or lo.

The best way I can describe it is a "fluttering" sound under throttle.

I apologize if this is an issue that has been beaten to death, but I honestly haven't come across this issue in my search. I've replaced one u-joint already and no change. Thinking I'll go ahead and do the other, but would like some other suggestions or scenarios.

The season is almost upon us and I'm scratching my head with this one, wondering if this is a common issue with the amount of lift. Rear Axle is shimmed and vibes are extremely minimal from the rear shaft.

Thanks

sounds almost likecould be a transfer case chain

Tcase was solid when removed- left it attached to the tranny when we did the swap too. Dropped the t-case on install too.

Could the front ds be too short after the lift?? The old truck had 4.5" lift, so that's 2" higher.

How have you isolated it as the front driveline?

Have you removed it to see if the noise goes away?

What is the front pinion angle?


The front shafts don't get too short, in fact with short arms and a taller lift they can get too long.

I have not removed the shaft. I'm looking at front driveline because the noise only occurs when 4wd is engaged and under load. The more throttle, the louder it gets.

As far as pinion angle goes, I have no idea- I'm a total noob.

Shaft being too long makes sense to me- that noise could be a slight binding of the joints?

Thanks for the leads!

if you dont wanna remove the shaft jack up the front end put the jeep in neutral, and spin the tire, and listen closely to the shaft see if you can hear a bad u-joint.

The shaft being too long won't bind the u-joints. Yours isn't too long, and if it was too long it would only be too long when the front axle is fully drooped out, and then it would damage the t-case output shaft bearing and not the u-joints.

Most likely your problem is pinion angle, but it could be a bad double carden joint, which could be aggrevated by a bad pinion angle. The pinion angle is the difference between the angle of the pinion shaft/yoke and the angle of the driveline. In the front it should be 0*, the pinion and the driveline should be lined up straight, or as close as they can be without castor being out of wack. Castor should be roughly 3-5* with that lift and the pinion lined up.

Adjust the arms to get the pinion lined up and see what happens, if the noise doesn't go away pull the driveshaft and drive it again. If the noise goes away take the shaft to a driveline place and get the double carden joint checked out.