1999 F150 XLT 4x4 with 5.4L.
9.75 Rear diff with ford LSD. I have the oddball year where the axle shaft diameter at the wheels is smaller than that of all other 9.75 Diffs.

A while back noticed when both rear wheels were off the ground and transmission was in neutral, if one wheel was spun the other wheel spun in the opposite direction.

Tore diff apart and found that the LSD has a bunch of broken clutches. Someone had tried to stack extra friction discs inside the pack, but the tabs got too close to the inner wall of the casing and broke off creating an open diff. After much cursing, I got the packs replaced in my driveway with dealership steels and frictions. Also replaced wheel bearings and seals since I was already in there.

So anyways..
Now my issue is that with both wheels off the ground and transmission in neutral, if I spin one wheel the other wheel spins in the same direction, however there seems to be 1 spot during the rotation the binds quite a bit on the drivers side. I'm thinking something to do with spider gears sticking?

Would a bent axle cause this?

 

No, you don't have a special axle shaft. The small diameter one was used from 97 up to 2000. They improved the diameter late 1999 and used in then and in later years.

 

Check your rotors first and make sure they aren't dragging at that one spot. If that isn't it open up the rear diff and see what you are working with.