Vibration at 3200 rpm and above need help

If your only change was the rear end and you didn't have the vibration problem before then it's probably the pinion angle:

http://www.moparts.org/Tech/Archive/axle/8.html

ALSO:

If there is vibration under acceleration, you need to add more downward pinion angle preload. If the opposite occurs, the vibrations tends to decrease or disappear under acceleration, you need to reduce the downward angle preload.

If the vibration steadily increases with driveshaft speed (either accelerating or decelerating) the symptom is primarily the result of a driveshaft imbalance or yoke runout. Sometimes this yoke runout problem can be improved by rotating the U-joint 180-degrees in the rear end differential yoke.

Driveshaft-related vibrations usually occur at roughly engine speed in high gear. Wheel/axle vibrations usually occur at 1/3 rd engine speed or driveshaft speed because of the differential gearing. To determining whether it is the output of the transmission or the pinion in the differential, change gears when the noise occurs and maintain speed. If the vibration/noise changes in frequency, the source is in the transmission or engine. If the frequency remains the same it is a driveline problem.


Good luck,
Treblig