Minimum distance for a drop axle is 9' 6" from center of rear axle to center of drop to be able to carry 43,000 as drive axle/drop axle group. Some years back 5 new T800's arrived with wrong diameter fuel tanks and drop axles set at 9' 4", all 5 were rejected. Not hard to figure how much net can haul, Jeff one of the old drivers was able several times to make 58,000 and some major change.