I have a 3:73 posi trac in my 80 Camaro I lit it up the other day and only one mark on the road never happened before, not making any wierd noises seems normal other than one wheel biting. This sounds expensive! It's a 10 bolt 8.5" Come on olebogie I need your wisdom.  

I think I'd right this up to Posi-traction being less than perfect. It's not like having a Detroit Locker, the posi will slip for a host of reasons. It might need a "tune-up" but if it's not making noises I don't think a rebuild/replacement is in your future.

The 3.08 in my LT1 powered S-15 will do that sometimes, at other times it acts like a locker. I think a lot of it is the lack of stiffness in a truck that lets the frame twist to where the rear end is loaded in strange ways, and certainly the lack of weight on the rear allows the posi to lock pretty hard vis-a-vis the weight on it . This especially happens in tight turns, which chirps the tires even when I'm not getting on it.

So I'd keep an ear out for strange noises for awhile, but I rather expect this was the effect of oil or dampness on the road, shape of the road, surface irregularities, a little twist in the chassis; more something like that which allowed axle loads to exceed the holding capability of the posi.  

Bogie

Well that makes me feel better, like I said it isn't acting any different other than what I told you. On a left turn when you put your foot into it it a little bit it seems to work fine, meaning it will jump side ways on the shift  Just another quick question on fuel mixture I turned both screws in all the way, than backed them out 1 1/2 turns , played with then until I got max manifold vac. seems to be alright but my pipes are black as hell with soot ( 600 edelbrock elec. choke)  

Z, you can check the condition of the posi unit with a torque wrench and an adapter to bolt the wrench to a rear wheel flange.  With the trans in neutral, and one wheel on the ground,  it should take about 40 ft. lbs. to keep the jacked-up wheel turning.  If you get enough torque, the posi unit is probably OK.  Any less torque, and you may need a new clutch pack and/or pre-load springs.   They're not all that hard to change, and may even be doable without taking the carrier out of the differential housing, depending on the vehicle (corvettes are out!).  

Check the plugs, if they aren't black then your OK. They're usually a redish to brown color and are dry. White to gray to little fuel, black soot too much, wet way too much or it's pulling oil over.

Pay attention to what Rfagin said, that's the test for your posi.

Bogie