So i did a thread about my rear end a while back, but i am still puzzled. I had thought my 8 3/4 was an open rear end, because it would only leave one mark (tire mark that is), but now it leaves two from a stop. Could it have been the 318 before didnt have enough power to spin both? Now i have a holley 650 vac secondaries, headers, and thumper cam with 360 heads @ 60 cc's. Before it would spin one tire, now it leaves two good dark marks, i was gonna buy another centersection with suregrip unit, but i do not want to spend the money if i dont have too. Could it be that its worn or does it need more power to spin both? Im just thinking about why it would only spin one tire. Oh and i drove it on the street today and it spun one tire again, is it at certain rpms that it catches? A certain speed? Or is it supposed to do it at all times? Please help me out on this, so that i do not have to buy another case. Thanks alot fabo members.