Ok I just had my tranny rebuilt 10,000 miles ago and it worked flawlessly untill one day it just started slipping into 3rd really bad. I mean 3 seconds to get all the way in. I only did this twice and then took it easy on it for a day or two without gettin on it. Then it started slipping at anything over 1/4 throttle in 3rd or 4th. So its all the way gone now. When I had it rebuilt i had them put in a b&m shift (i know, i know i hate it too) vett servo and extra clutches in the 3-4 pack What caused it to let go? I'm only making about 300 hp on a good day. This tranny should have taken it. I'm pretty familiar with the 700 so i'm looking for a technical answer, so you won't scare me with an in depth technical explanation. What does the trans-go shift kit do to help with this problem? Did the b&m shift kit do this?

The B&M kit really does nothing for 3rd gear. Adding clutches can sometimes help, but if nothing is done to fix the "inherent" problems to begin with, then adding clutches might not do much of anything. The Trans-Go Shift kits address the problems and will give you the quick shifts that you want. You already have the Corvette servo so add the Trans-Go Shift kit along with the larger boost valves, Borg Warner Hi-Energy 3-4 clutches, and Hi-Energy 2-4 band, and have someone who is competent with the 700R4 unit to build it for you. If you can not find anyone to do it right, call me, as I specialize in 700R4's.