How much weight can you legally haul on a single axle dump truck?

Well, it depends on what it's licenced for. If it's a 26,000 lb. GVWR vehicle (which doesn't require a CDL, such as the Ford F650), five to six tons, typically. For a 33,000 lb. GVWR vehicle, eight to nine tons. 33,000 lbs. is the federal interstate weight allowed for vehicles of this type - in many states, intrastate drivers may gross up to 40,000 lbs., depending on what the state allows, vehicle length, etc.