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
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1 answer 3 comments
ANSWER by , April 17, 2012
did this problem happen after the trans replacement?
COMMENT by , April 17, 2012
Yes it did
COMMENT by , April 17, 2012
CK YOUR TIMING, FUEL PRESSURE AND PLUG WIRES TO START
COMMENT by , 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??