Bad Front diff binding stumper

[rustyota]

Ok, in my 90 4runner (auto tranny), the 4wd binds up pretty bad. The problem is, I don't know where it is originating from.  It runs fine in 2wd even at high speeds, just the normal vibrations, no binding, steering and brakes ok.

But, when I put it in 4wd (auto hubs) and let my foot off the brake it barely moves just idling. If I give it little throttle it moves, but as if I am staying in 2nd gear (let off throttle it almost slows to a stop). Once I get up to about 15 mph on pavement there is pretty bad vibration, a nice low rumble, and the steering wheel goes kinda haywire, not pulling one way or another, just shimmying back and forth.

The weirdest part is when I stop and, with my foot on the brake, take it out of 4wd. The entire body lurches up about an inch, as if the 4wd is pulling down on the springs while it is in gear.

About 1 year prior to this, I replaced the cv joints, rotors, and calipers. But this problem all of a sudden started about 3 months ago. One day it is working fine, and the next day I put it in 4wd and bind city.

I have been trying to figure out where the problem lies but it seems like it could be anywhere from the tranny to the front tires, and I know little about the transfer and IFS diff.

[FIREBALL]

Did you replace a 3rd member at any time? Differant gears? Are you testing on hard ground (pavement)? Have you checked tire pressures to make sure they are all even?
Those are the only things I can think of.

[reklund5]

I've seen front driveshafts all worn out from sticking auto hubs causing them to spin all the time...

The front driveshaft (especially the slip yoke) often gets ignored for lubrication at the grease fittings- maybe there's just a bad Ujoint in the front driveshaft?  The slip yoke is maybe bound up? 

Crawl under there and investigate!

Ryan