Is my 12bolt a posi??

[mikep]

I dont think you have a posi carrier. I think someone at one point did the old poor mans posi trick in your differential and added shims between the differential cross pin and the spider gears. Theres different ways to do it but in your case it added a bit of preload between the axles. Its not very effective and it causes a lot of wear to the differential cross pin and to the spiders. I'd take the washers out and remove the cross pin to check for damage and the spiders as well. I'll bet you'll find a lot of scoring of the differential cross pin . For the cost of new parts you could probably find yourself a good used 12 bolt limited slip carrier.