dumptruck tranny
If you are hauling gravel in a mountainous area, or out of pits, a 15 or 18 speed tranny [ 4 X 4 or other deep low gear arrangement] will pull out of many places that a 13 speed will be unable to start because their lowest gears are lower than the 13 speed. ( 9 ,10 and 13 speed trannys are great for road apps but will wear out your clutch faster on off road)
There are places that our 15 speed dumptruck can work that our 9 speed dump truck cannot work because of the need for very low gears.
Our heavy haul truck, a 379 Pete 425 hp Cat, 13 speed tranny on 4.11 rears and triaxle 55 ton detach must carefully choose loading positions to accomodate the the transmissions lack of bottom end. If I am moving a 200 size hoe ( about 50,000 lbs) the transmission is less critical than when I move a 300 or 400 size hoe. Obviously dumptrucks must come and go from places with steeper hills than heavy haul trucks so this concern is magnified.
Specing a truck requires talking to people who use them to get the operational insights and talking to builders and manufacturers to get engineering insights.
The choice of wheelbase and box size is shaped by your area and intended cargo. 3000 lb a ton gravel can reach weight limits in 13 to 14 feet of dumptruck and if you're delivering in a mountainous or confined areas may cause you to choose shorter wheelbase trucks.
If you're in a state, like Mississippi, that has hundreds of short old bridges, bridge length is important. ( how many axles of your truck are on a short bridge at the same time is what bridge laws are all about. A longer truck can carry more because the front axles leave the bridge before the back axles reach the bridge). There are other states where bridge length is a lesser issue.
Many states allow tri and quad axle dumps so axles and axle spacing may impact your wheelbase decision.
Another thing to think about is this: if you spec the truck too tightly, you reduce the things you can use it for and the potential resale market. If you spec the box real small you may have made it more difficult to haul chips and mulch, stumps, trash and other things and reduced your potential earnings.
As someone else mentioned, although you can find lots of old road tractors at reasonable prices, a double framed dumptruck chassis is superior for dump trucking. The road tractors may or may not have rears rated at over 40,000.
One person mentioned bobcat loading of dumptrucks and dumptruck wall height. If you are loading dumptrucks from the ground ( loader style). Either dig a depression that the dumptruck can back into or build a ramp to climb with the loader. Even if you are not having trouble with reaching the dump bed, it will shorten your loader cycle and save time and fuel if theres much materials to load.
I have 35+ years of transport of everything from D-9 dozers, Patriot Missile Warheads, to AC DC Band tours. We have run as many as 46 trucks at one time.
Good luck with your new truck
