XPTB

I recently installed a slip yoke eliminator with no issues a few months ago, and changed to 4.56 gears. At the time I moved the front driveshaft to the rear until I could get another one. After getting another one (supposedly new and balanced), I get bad vibration when getting above 50 mph. I figured it was the driveshaft so I borrowed a friends, which works fine on his XJ. In mine I get the same vibration.

Now I'm thinking something is wrong with either the gear swap or the eliminator. Is there someway to test either of these for the vibration? I am within spec for backlash in the front. If I take the front driveshaft out, It drives smooth. All bushings/joints have been replaced as I'm setting this up to DD/mildly offroad.

1999 XJ 4.0L AW4
4.5" lift with new 33s
4.56 gears front and back
slip yoke eliminator
ZJ tie rod

tech

Lift your jeep off the ground on jack stands run it up and see what off center and making it shake .

XPTB

When you say run it up, you mean put all 4 wheels off the ground and "drive it" up to like 50? I didn't think the diff liked moving fast with no load

tech

Yes they don't like running that way but your not going to run it vary long . you just want to see where the shake is , all it takes is a few minutes it will be OK

XPTB

ok thanks. I'll try that this weekend and report back.

Jackem

IMHO it's not a good idea to run a vehicle with driveline vibrations on jack stands. Use extreme caution and have a clear runway in front just in case it falls off the stands

tech

Also put the jack stands under the axles so the suspension is the way it is when it's on the ground. it is safer to have 2 people one running the jeep and the other looking at what's happening .