WHAT WOULD BE THE CAUSE? MY TRUCK IDLES FINE IN GEAR IT MISSES BACKFIRES W2DIE? on 1990 GMC 1500 Pickup

I JUST CHANGED FROM THE 700R4 BACK TO THE TH400 . ALL GEARS WORK GREAT. IVE CHANGED FUEL FILTER N SPARK PLUGS. ALSO PUT IN A FABBED KICKDOWN BUTTON. DONT KNOW WHERE I SHOULD HOOK UP THE WIRE TO SEND SIGNAL TO TRANNY TO KICKDOWN?

by in Rochester, WA on April 16, 2012
1 answer 3 comments
ANSWER by on April 17, 2012
did this problem happen after the trans replacement?
COMMENT by on April 17, 2012
Yes it did
COMMENT by on April 17, 2012
CK YOUR TIMING, FUEL PRESSURE AND PLUG WIRES TO START
COMMENT by on April 17, 2012
Sorry I've been trunk to change me answer. No it had the problem. On drive him after I paid for it. It showed them signs. Top radiator hose collapsed. I've done my fuel fillter,spark plugs. I'm about to do my tos??