i have a 1995 e 350 with a grabbing in the rear. It sounds and feels just like the rear brakes are too tight, but they are not. They have been replaced just in case, but didn't help. the hub bearings and u-joints have been replaced. The third member has been inspected and cleared. The hotter it gets the more severe the problem and if you raise the rear off the ground and run it... the problem disappears. thats why we changed the bearings.
Two independant mechanics and the ford mechanic were stumped by this problem and gave up. We have adj the rear brakes till they are non functional and the problem still exists.
I...along with the mechanics, am stumped.
Any suggestions??? H E L P !!!

 

you might want to post this in the 1968 to present van forumn. good luck

 

Did anybody replace the proportioning valve? As long as you're throwing parts at it...

 

It sounds like you have a limited slip differential and the clutches are grabbing.

 

i agree, but i understand there is not much you can do. I have changed the diff fluid and added an additive for friction, but not much difference. Odd thing is it won't act up when cold, but increases as the diff. heats up.
only feel it while turningbelow 5 mph.

 

this sounds typical of a locker or posi-trak system to me...

My Detroit soft locker, is very new and it grabs (chirps tires) a little at lower speeds while cornering.

If you don't have any noises or issues at higher speeds you're probably OK.

My 2 cents.

 

I also think it could be the limited slip clutches acting up. Or if nothing else maybe one of ther axles tubes is slightly bent. Good luck on this one...