Correcting Jeep Driveline Vibrations

One problem that is generally encountered when installing a suspension lift kit on a Jeep is drive line vibrations.  As a vehicle is raised, there becomes a greater angle between the output yoke of the transfer case and the input yoke on the differential.    This increase in driveline angles can cause the driveshaft to vibrate.  One of the best cures for this is to install a Slip Yoke Eliminator Kit on the transfer case.  SYE Kits replace the sliding rear yoke with a permanent yoke and incorporate the use of a slip member style driveshaft with a double cardan joint on the front end.  These drive shafts are commonly called Constant Velocity or CV Driveshafts. 

The SYE kit comes complete with a  rear housing, output shaft and solid yoke along with the required hardware for installation.  The installation is very straight forward and can generally be completed in a couple of hours.  It is best to remove the NP231J Transfer Case from the vehicle but can also be competed while still in the vehicle.

Drive line vibrations can also be a result of changing the gear ratio of the vehicle.  Quite often a vibration will not be noticeable until the gear swap is made.  This is because that if you increase the gear ratio of the drivetrain, the driveline actually runs at a higher speed.  For example if you currently have 3.07 gears in your vehicle and replace those with 4.88 gears you have increased the gear ratio by 59%.  With this change, the driveline will actually run 59% faster as also.   Therefore a vibration that was only prevalent at high speeds will now be noticeable at a much slower speed.

Correcting this problem is very easy theoretically.   You simply need to decrease the angles of the driveshaft.  It is important for any drive shaft that uses a single u-joint on each end to have the angle on the front u-joint be equal to the angle on the rear u-joint.  If these angles are close, there will be a vibration.  If you are unable to match the front and the rear angle, you may consider a Constant Velocity driveshaft.  A CV driveshaft decreases the angle and allows you to rotate the differential so that the rear angle is greatly decreased.  This can be accomplished by the use of wedges, relocating the axle spring perches or twisting the axle tubes.