Bump induced vibration

[Casey Scogin]

This one has me a little stumped.
Bought my new 76 Scout over the weekend and it drove home fine. Now a couple days later I have a random vibration. As I am driving if I hit a bump while going over roughly 20 mph I get a slight vibration in the rear of the vehicle. It feels similar to a wheel rubbing in the wheel well. Then as I slow down to around 5 mph the vibration goes away. I can then speed back up and there is no vibration until I hit another bump. It has a 345 with auto. I am thinking it could be a wheel bearing but am not sure. If anyone has run into this please let me know.
Thanks

 

[Scoutboy74]

Check lug nuts for proper torque, spring shackle mounts and bushings, look for cracks or stress points in the frame where the shackles are welded on, check spring u-bolts for tightness/breakage, shocks and mounts, rear driveline at both ends for excessive travel at the joints, and the potentially most dangerous and destructive of all...like you mentioned, rear wheel bearings. If you can't be 100% sure of the maintenance history on those items, you need to replace them for peace of mind. Use only timken set 10 bearings. Vital that you accept no substitutes. Pulling the axle shafts is no big deal if you have tools and are mechanically inclined. Pressing the old bearings off and the new on does require a press. You should be able to find a machine shop to do that job for a nominal fee. How are the rear brakes while you have the drums off? Might as well have them re-surfaced and new shoes installed if needed.

 

[Robert Kenney]

Another thing to check is tire pressure. To low tire and an axle with worn shocks can bounce (resonate) at a low speed as you witness.