Have 4 to 4.5 lift. SYE with front drive shaft from another XJ as the rear drive shaft for the SYE.


Up until a few weeks ago I had nearly 500 pounds combined weight of front and rear bumper with winch. This had me sitting about where a 3 inch lift would put you. Sold those to build my own tube bumpers so my XJ now sits up higher. About 2 weeks after removing the bumpers I started hearing and feeling a vibration. Most noticeable around 50 to 55 and its only when under load. If I'm uphill its worse. Downhill I can get out of the accelerator completely and it goes away. I put it in neutral coasting down hill and revved motor to see if vibration was there but its not. So I concluded its only when under load and I'm thinking it might be the increased height and changed angle.


Looking for advise and where to start. I considered to removing the front drive shaft but since its in 2wd and the front is not under load I doubt that's it. The next step I guess would be remove the rear driveshaft, drive in 4 high (front wheel drive) and see if the vibration still exist. My concern is if it does not exist I have only eliminated the rear drive shaft and that it might be something in rear axle. I do not know how to check that since if I hook rear drive shaft back up it is now back in the loop.


If the vibration exists in front wheel drive mode then I would think the problem is somewhere in the transmission ?


Just need advise on running this down because it is my daily driver and I'm not the type to just drive it till something breaks and ends up breaking something else.

 

Use an angle finder to check drive shaft angles, shim according.

Quick test, swap front and rear shafts to see if problem goes away. If so, rebuild rear shaft.

 

Did you rebuild the rear driveshaft before installing in your XJ with the SYE? If not it could be the u-joints giving you the problem.

 

My xj would vibrate under load. Thought the front u-joints were bad. Replaced them still had vibration. REMOVED front drive shaft. Still had vibration. Examined rear drive shaft u-joints by hand and eye, everything looked good. Made me crazy. so I replaced the u-joints in the rear shaft and now everything is smooth just like it should be. So just because you can't move the u-joints or see them bad, under a load they can be bad. Mine were. SO just FYI....might change rear u-joints just to make sure. 73' de AA7KN