My 88 had a shaking problem like yours that was the worst at 45 MPH. The tires were re-balanced over and over to no avail. Finally this last Saturday the problem presented itself. The Rear diff carrier was cracked and off center in the diff. Saturday the crack opened up to the point where it rubbed the pinion gear and then broke while I was driving!! The broken pieces of carrier were then "chewed" by the ring gear, and the side gears. When I pulled the cover off the diff many small and big metal pieces came out, it was not pretty. Now I am replacing everything inside the diff housing: pinion, ring, carrier, side gears, bearings, LSD clutches, shims, everything. If I spend less than $600 on parts alone I will be suprised.

I would check that rear diff again.

BTW - If anyone can help me get a good deal on the whole diff assembly with 3.55 gears and LSD in the 8.8 Ford diff, I would greatly appreciate it. E-mail me.

Thanks,
Randy
randygaz@asapnet*spamremove*.net

 

I have a 94 F150 with the identical problem.
I have replaced all 4 tires, all 4 wheels, complete new front and rear brakes, new universals, drive shaft balanced, run out has been checked, rear end has been checked. Also, I have had it run up on a lift. It shook like crazy at 40 with the wheels on, but smoothed out with the wheels off. I disagree with StunningJ. This isn't something we should have to live with. Too many other owners are having the same type of problem. Check out the Shadetree Mechanic Web site. I think we're talking class-action!