I heard this pop and then....

Actually I heard a pop when I was accellerating away from a stop sign and then it felt like the rear end was slipping. I would give it gas and hear a low moaning sound from the rear and the car sits still even though in gear. It is a 4 speed with a 8 3/4 clutch type sure grip. Is there something in the clutch that would make 1 pop sound then not function. I wasn't "gettin on it" when this happened and if I only apply lite acceleration, the car will move a little until it starts to slip as my foot goes further down on the accelerator.
If it was a broken pinion, wouldn't it make a lot of racket and not move at all?
What sucks is that I just put this rear in the car 2 months ago and have been unable to really drive any until now. And now it's broken again..
I bought it used last year and just got it in.
I hope it is just the clutches inside the thing that are broken.
Does the ring gear need to be removed in order to fix the clutch pack in the rear?

Dan