I have a Ford F350 1997 2WD with input bearing problems

.Question  I have this F350, engine has been enhanced slightly. Now there is a problem with the main bearing in the gearbox. it has broken down three times already, it only takes a few moments when it breaks down again (less than 500km). the last time we replace the bearing, box carefully cleaned and oils are certainly great quality. Now I wonder whether it would be too much engine power, or can be caused by a fault switch or lubrication? because the engine has been changed more powerful should the gearbox to make improvements?

Answer: There aren’t any updates to the bearings. Be sure to Merc V ATF in it and it is ok to overfill by a quart. It is also probable that there is  a pre-load problem (too tight) causing the premature failure.  See parts we provide for the Ford ZFS547.