Truck Repair: transmission problems, torque converter clutch, lockup torque converter

Question
my brother is currently in guam with a 95 ford bronco, the transmission is slipping at certain speeds the techs helping him there have changed many parts and now they want to change the instrument cluster, incase there is a sensor in the speedometer or tachometer or somewhere that sends a signal back to the tranny, this sounds ridiculous to me. so that is my question is there anything in the instrument cluster that can cause a tranny problem to effect shifting

Answer
Nothing like that that I am aware of.
I would ask if they changed the tranny fluid and filter, and if they looked at the o ring on the filter to make sure it isn't sucking a little air.

They could have a lockup torque converter clutch solenoid valve opening. It could be effected by the throttle position.

Van