Anyone know how much weight a 1987 f350 diesel dually w/ 235K miles w/ a enclosed box in place of the bed can hold before either the axle or the frame will snap. my boss insist on loading 5+ tons in his truck with shingles before taking it to the dumps to unload!

 

Since this truck is used for commercial purchases there might be some legal issue with overloading. Look for sticker (probably inside the driver's door) that has the truck's weights and capacities. Have your boss weigh the truck loaded and compare it to the GVWR - Gross Vehicle Weight Rating. If he exceeds that he may be breaking the law and certainly surpassing the manufacturer's recommendation.

I'd try to find a F350 forum to ask this on. Those guys know everything about weight ratings.