Quirky Center Differential

[graf703]

So when I originally bought this project car and got it running, the tires would drag during tight turns. It would pop and shimmy and it had horrible oversteer in the snow. So I figured it was a welded center differential. Suddenly a month ago it stopped popping and shimmying in parking lots and I can actually do a U turn! But now in snow it seems like once tires are spinning it doesn't drive the rear wheels.... But if I launch the car dry it just hooks up and never spins any tires... In the rain two weeks ago I got into a little bit of a front wheel slide in a turn and when the tires gripped again there was a large noise from the front like a pop and the car sort of jerked. Also, the output shaft to the transfer case slides in and out which I understand is abnormal...

Any ideas on what is going on here?

Is there a diagnostic procedure besides taking off the side cover to the transmission? Thanks guys!

 

[graf703]

So I've decided the viscous coupling has gone bad... How common is this? Anyone know how much it costs new? Part #?