Bumpin' an old thread. This has happened to the ADD diff in my 87. The seal started dumping oil, so I went under to inspect and found a wicked wobbly shaft. The cause of this is bad bearing in the carrier correct?

Little bumed since I put that diff in 7 months ago, and would hate to have to pull it out again.

 

Having a similar issue in my 94 4runner. I was getting a wicked rotational grinding and vibration in 2wd. Took it to a local Axle, Trans, transfer and gear specialty shop. They replaced the inner and outer wheel bearings on both sides up front, replaced what they said was a bent rear axle on the drivers side, and replaced a leaking rear pinion seal. I picked it up, drove 3/4 mile and low and behold ... the same vibration and grinding. Located some serious play in the passenger side output shaft on the front dif. I pulled the dif, front prop shaft, and both cv axles (which were replaced about a year and a half ago. No more grinding/vibration. I did notice a little brake wobble after the dif issue was removed. Going to tear into the dif today. I will update later (hopefully with pics) on what parts replacements wind up curing the ailment.

 

That buzzing/ vibration is probably the needle bearings, I have a 1990 with ADD and pulled the diff to find gravely sounding needle bearings. Hope this helps. It might also fix your wiggling shafts.