transmission won't engage.

[mike.dukes]

I was going down an onramp when there was a loud *THUNK* and from then on the trans won't engage in any gear. Just makes a weird winding noise. its a Automatic trans on a 4.0L '91 mazda navajo. Any thoughts on the cause?

 

[BrooklynBay]

Maybe your differential got stripped? Check to see if the driveshaft is turning when you hear the noise while you are sitting in one spot (while in drive or reverse).