Spec'ing a Truck for the Lighter Side of Heavy Haul

Wow, lots of questions....
Dump the super single tires. Not rated for enough weight IMHO, and will put a world of hurt on you if you have a bad tire etc. Look at the sidewall of the tires though, to see what they are rated for. In some states you can go over 40k lbs, and the easiest way for a DOT cop to ticket you is if your tires arent rated for it!
Looks like the engine, clutch and tranny are up to that weight, no problem.
What rears does it have now? Suspension? If it has 40k lb rears in it now, and the gearing is not too tall, then keep it as is until something starts getting noisy etc.
Forget about the double frame, just keep the front at @12k lbs, and the rears around 40k lbs, and it will be fine. A double framed truck is doubled inside the frame rails, so it does not make it wider etc.
Make sure to get some good ramps on there, as the ones I have seen on ATS trucks are all but useless.

Martin

 

double frame is a 1/4" c channel frame inserted inside you rail widen the rail no thicken it yes most shops only double frame from the back of the cab to the rear a factory is at least to the front axle pretty low rpms to be pulling a load its near impossible to get great milage even a piece of equipment that weights 30k on a lowboy is going to pull alot harder than 30k in a van or covered wagon

 

You've got a better transmission and more power than my company truck I've got. I've only got a 475 ISX with a 16913 transmission and 3.55 gears on low pro 24.5's. The truck I've got was stretched, lined and an axle put under it. Used it like that with a 4 axle lowboy for a few years. Now have a jeep to go with it. Grossing 160,000 lbs. Only compaints are low power, and should have a 18sp for the lower gear starting out.

 

leave it alone you have more than enough truck for 120000lbs. double frame does not make a truck wider every truck has enginering in it for a variety of setups. i will bet your cross members have slots in some of the bolt holes to (shrink) the crossmembers for an insert to be slid inside of the frame you have. but like one poster said, you really dont need it. dump the super singles.

 

I'd like to buy a period for $200 Alex

 

I may be showing my age but that wouldn't that be either Pat Say-jack or Chuck Woollery?

 

I have ran oilfield heavy haul for last 5 yrs running many dif" spec'd trucks, I wouldn't go lower (numerically) than 3.91, I currently run co truck ISX 550 18 speed, remember 18 are double overdrive that really hurts trying to maintain speed up hills which where your going burn the most fuel, same spec truck but with 4.30's overall runs much better, I know all the highway haulers will disagree, but they don't weigh 67k empty, overdrives reduce torque to ground, great for high speed doesn't help HH so I would look at the eaton fuller gear ratio calculator work from 16th 1:1 to determine which ratio with tire OD will work best

 

Follow you fully, but the OD is the tires overall diameter . Some may have read over drive instead.