1994 Ford Bronco Mr transmissions keep going bad

Transmission problem
1994 Ford Bronco V8 Four Wheel Drive Automatic

I have a very nice '94 Bronco with a 351 engine in that keeps blowing out transmissions. Several years ago while in Santa Fe NM my tranny went bad and I had it towed into the local Ford dealer for replacement. They put in a Ford reconditioned tranny and it went out on the test drive. So they put another one in and I didn't make but a few miles and it went out again. They said that because I had a Super Chip installed in it that is the reason that the transmissions had gone bad and if I wanted my Bronco fixed I needed to pay for another and remove the Chip. Being 600 miles from home I had no choice so about $7000.00 later I drove away. That tranny lasted about 1,500 miles. I replaced that one with one that I got from a junk yard and it lasted about 200 miles. All of the symptoms that I have experienced with all of the transmissions are about the same. Driving down the road I start to hear wirring and loud sounds. When I stop I can not get the vehicle to go into reverse and barely forward. If I let it set and cool off I can coax it in reverse or forward but you can tell that it is about ready to totally lock up. This is getting very expensive. I did send the Super Chip to the factory and had it tested and they said that it was up to the factory specs and that it would not cause a transmission to go out. I called Ford and complained about the dealer screwing me out of two transmissions and they said that they stand behind their dealer 100% go figure! Do you have any ideas?