I met a guy that is selling a 99 WJ with the 4.0. He's done a lot of work on it. He has replaced the weak head on this Jeep and its got nice rims and tires. It either came with a lift when he bought it or he added it. He has death wobble or at least a vibration at about 45 mph.. He can't figure out why.He's fed up and selling it for way less than he has into it, just because he can't solve the vibration issue. He said its a 2" lift, but it looks bigger than that. He is thinking the u-jonts in the axle are bad. I have not dealt with this issue before. I thought the dana 30 came with CV joints and one simply replace the whole axle I have also looked at parts diagrams for the D30 and saw a u-joint. Help me sort this axle,vs. cv joint issue out as I am trying to help him or may even buy it if its just a matter of replacing axles. Thanks.

I'm thinking the splines on the front driveshaft are worn and causing the vibration. The driveshaft on my 2000 WJ 4.0 has a double-carden u-joint on the t/case end, and a CV on the diff end. The center has a slip joint with splines and a lock nut to adjust it's length and I'm willing to bet this wasn't adjusted after the lift. This puts tremendous stress on the CV joint and may be the source of the problem. The locknut may have loosened and now the shaft is wobbling in the center.

Grab the shaft in the center and see if it moves up and down.

The drive axles are CV joints and are usually changed as a whole axle unit.

Thank you Dave.

D30 front has U joints at each knuckle, but those going back won't cause DW. They can cause vibrations (also the drive shaft), but not DW.

A few joints that can go bad and can cause DW are: upper and lower ball joints, either end of the upper and lower control arms, steering box mount to the unibody, pitman arm (unlikely), drag link to tie rod, tie rod ends, track bar ends.