I have an 87 F250 4x4 with a 5 liter auto. While I am driving, warm or cold, if I hit a bump with the front end(especially the drivers side)I get a very strong vibration with a dull roaring type sound coming from the front end. I can feel it through the floor and the passenger can feel it through the floor also. Strange thing is, if I go over another bump in the road, most of the time the vibration goes away. If it doesn't go away, as I slow to come to a stop it keeps going until I am at a complete stop. It also doesn't seem to change "pitch" with RPM, actually gets louder as I go slower. I thought it might be the front slip yoke, but the driveshaft doesn't turn when the 4 wheel is off and the hubs are "free" right? It has manual hubs. Any ideas? It is bugging the heck out of me and it feels like the whole front axle is going to fall out. By the way, it gets worse if I spend any time at highway speed.





The harder you work, the harder it is to surrender...

 

Have you checked the wheel bearings yet? As for the front driveshafts, you can hang your head down and look under the truck while moving it a little to make sure nothing is moving just to give yourself some peace of mind. Nothing should spin unless the hubs are locked in.

 

Check your shocks. I had a similar problem on my 92' and it wound up being the shock bushings. My shocks were approx 3 to 4 years old. Also, check the bolts that hold the pivot point of each half of the front axel to the frame. I had these come loose do to oil build-up underneith the engine. good luck.

Jakegypsum // Ford fleet, soup to nuts.