HeavyBreathinRS

I have a '90 RS, 305 TBI, with (I think) the 4L60 auto trans in it.
Reverse never seems to slip, but if I set the trans into 1 or 2 or even D to start off, the trans slips and growls like a wounded bear. If I start off in Overdrive (D circle), it pulls away normally under light to medium throttle, but definitely slips under heavy throttle.
Shifting seems smooth enough, and kick down (both halfway and pedal to the floor) works fine i.e. no growling, although it does slip.
I just finished reading a thread where people were discussing slip on a posi...this beast has been savagely modified by some backlot cannibals, so it's entirely possible that the rear end is not original.

So my questions are:
How can I tell if I have a posi (that's maybe slipping)
What ideas does the group have (I plan to do a swap to T-5 next year anyway) in view of the fact the car is still very driveable?

Thanks

82camaro

It's not the rear end, it's the tranny. A slipping posi(worn out) will allow one tire to spin during a burnout. Gear selection has no effect on the rear-end(it doesn't know what gear the tranny is in). If it's stock, it's not posi--want to know for sure, pull the cover. IMO, get yourself a good rebuilt tranny.