4L60e design flaw
it is a 4L60E. they are notorious for crapping out early. i have heard many complaints of them failing at 30K miles. mine died at 115k. i paid $1200 to have it rebuilt with a shift kit, beast sunshell (a must!), corvette servo, alto clutches/steels, auxillary cooler(from z71 package) and the valve body fix with a 2 year/24,000 mile warranty, o yea and the 2 u-joints on the front driveshaft. Jeff Holt is my boy! ask me if you need his info. his shop is in charleston, south carolina and he can hook you up!
if your symptoms are a hard bang from 1st to 2nd gear then you got the same problem as most of us. the valve body (thing that controls fluid in the tranny oil pan) has a design flaw. this little hole gets reamed out and causes the computer to turn the shift pressure up WAY too high which makes the tranny tear itself up. they have an $80 kit to fix this but if your gears and clutches are burned up... you gotta pay big bucks to replace that stuff. don't let the dealer charge you over $2000 to put another crappy transmission in there!! call around to local tranny shops and get a quote for less than $1500 to rebuild with a warranty. but first get them to change the fluid/filter and update the VALVE BODY
as far as how many bolts are in it i have no idea but it's definitely a 4L60E
