Best used truck(brand and model) to start with?

I am not sure why you need 40,000 lb rears, but an aerodynamic truck will usually offer the best fuel mileage. As the driver, you are the most critical factor in how well or poorly your fuel mileage. I prefer 355 gearing or something close. I get decent fuel mileage while having good pulling power. Freightliners seem to do fairly well on fuel mileage, as far as brands are concerned. Volvo's also seem to do well. It may be more difficult to find 40,000 rears in those brands than something that is considered more heavy duty, such as a Pete or KW. I have had very good service from International and gotten good fuel mileage. I have also done well with KW. I would stay away from the automatics unless you run a lot of city or heavy traffic areas where you do a lot of stop and go. Repair costs are significantly higher with automatics than manual transmissions. You could probably buy an automatic for less than a manual, but having driven both, I prefer manual.

 

2 peddle automatic or an autoshift?

Mack, Volvo, Int'l will probably have the most used choices with an auto vs. Pete, KW or Freightliner. I'm biased, but I would look for a Mack CXU '08 and newer, one thing to becareful of, anything newer than '09 will have the latest emissions equipment, so you need to plan for that. Knock on wood I haven't had any emissions issues in the last 8 months with mine, but earlier on we has several. If it's a retired fleet truck, anything over 400K miles should be fully broken in and have all those kinks worked out. Mack, Pete, KW will be the heaviest, Freightshaker and Int'l the lightest. The biggest expense on an autoshift trans will be the x/y shifters, about $700 to $1,000 depending on the source. You can generally expect to get 300,000 to 400,000 miles out of a set, maybe a 40 minute swap out with basic hand tools.

I currently drive an '09 CXU, Mack MP8 engine 445/hp, Eaton/Fuller 10spd autoshift 48" flattop sleeper, it's 392K on it now, aside from the size of the sleeper I love it. Our trucks are gov'd at 78 mph (75 on cruise), I can run Denver to Sterling, Co. empty out and 80K back and avg. 5.3 mpg rnd trip. If I keep it to 65 mph I'll get 6.5 to 7.0 rnd trip.

A good place to start is www.truckpaper.com lot's of listing and you can break the search down by area and features.

 

it just all depends on what you will be doing with it, how much you have to spend,your needs and likes. OTR, heavy haul, hauling products paid by the weight, fifth wheel height, dealership close to home, etc. Have 20 grand to spend, or 60 grand ?. You like a basic work truck or need the bells and whistles ?As far as trucks, it is hard to beat International & Freightliners when purchasing used, and they seem to have a good dealership network.
I just prefer the manual, not sold on the true automatics, but auto-shifts seem to be working out nicely for some applications.

 

you really cant go wrong with a freightliner.