Hi I'm ordering a little peterbilt 335 for my farm. I pretty much looked at all brands in this class 33KGVW and they seem to come standard with some make of engine rated at 260hp/2400rpm and 620 lbs of torque. Of course you can up grade drastically depending on company. Peterbilt offers thier Paccar PX-6 ( the new 6.7 cummins ISB) or the PX-8 ( the 8.3 cummins ISC) in the 335's. I went with the 6.7 cummins rated at 300HP/2600 rpm and 620lbs of torque@1600rpm. They suggested I go with the 6 fuller speed manual trans and an axel ratio of 4.11. I wanted to be sure I'm not reved out too high on the highway like my old truck. So then they suggest I go with the 6 speed fuller overdrive tranny and a 4.88 rear axel ratio. With this trans and axel combo this truck is suppost to cruise at 62mph @ 2000rpm down the highway. This seems to make sense as then I'd have a lower 1st and reverse gear with the 4.88 axel compared to the 4.11 or 3.90. The truck will not be carring its limit in wieght ever but it will have to buck a lot of wind when loaded as the load sits high and is 10ft wide. Of course I have no way of test driving this truck as they don't have the exact one on the lot and it wouldn't have my hay mover rig set up on it anyway. But I guess it would be similar to a box truck for wind drag etc. The present truck I'm using is a F700 ford with the 370 gas engine in it. I don't even know the hp, I imagine around 190-200hp?? The engine is underpowered for the job. On flat ground with no wind it can pull the load fine but I have my foot into it. It has the typical older truck low gearing so its just screaming (like 3000-3500 rpm)on the highway to get to 60mph. If there is any kind of head wind I have to pretty much stay home! I'm hoping some of you guys have single axel trucks with similar gear ratios. Do the specs the dealer has recomended sound about right? They also tell me I should expect to double my fuel milage from 5mpg to about 10mpg.