i believe it came with a 4L60. I just got mine tranny redone, went from a 1,900 stall (which is stock) to a 2,800 stall converter. I'm putting in a 3,500 in a few months after my exhaust. I got the 2,800 for free from a friend
. anyways, i got new clutches, and get energy suspention mounts with a B&M shift kit. To top is off get a 100 wet shot of nitrous and a soild exhaust system with headers and you'll see high 12's in no time!