What is your pin weight on that trailer? It sounds like a single axle will be more than enough for that trailer. Your rear axle rating on a air ride Class 7 or 8 is 20,000 lbs and a toter isn't going to add the weight as a motorhome would to the rear axle. Talk to Larry Ziegler on this, he always blows out the second axle on the tandem when he sets up his RV toters and I know those trailers are easily 12,000 lbs plus.
A tandem axle is better if your off in soft terrain such as grass pits or muddy parking areas. I would only look at 40,000 lbs rear axle rating if I was 2000 lbs or closer to the max rear axle rating on a single axle.
A tandem axle will not give you a better ride on the highway over a single axle. If my rear axle weight is let say 18,000 lbs and I have a 40,000 lb rear end it is going to ride rough. On my rig, if I air my rear bags to the max 120 psi, it rides rough and I would say my rear axle weight is around 18,500 lbs. This still leaves me 1500 lb tongue weight before I would trip the lights on the turnpike.
Remember, if you go with a tandem setup, you have 4 more tires, 4 more rims, 2 more sets of brakes, 2 more airbags, another axle & gears and more rolling mass to chew up fuel. If you don't need the second axle you can save yourself money in the long run by not having it. This is why it is important to figure out what your weights will be and what your weight requirements are.
If you have driven a manual non-sycro trannie before and like it, then you can save yourself alot of money on a used class 8 for your toterhome. It sounds like you haven't, and if that is the case, it will be easier to go to a auto shift, but tougher to find one. Once you get the hang of a manual, you will be able to float your gears (no clutch) and even in heavy traffic I have no problem laying off the clutch and just giving myself a alittle room in front of me to keep on rolling.
Since your on a budget, your best bang for your buck will be to find a used Class 8 with around 500,000 miles on it. You can find good ones for $25,000 on up that will have 350 hp on up.
2003 28' Show Hauler Motorhome on a 1995 FL 120 www.showhauler.com
[This message was edited by warpath on December 04, 2003 at 10:17 AM.]