Gearing should be good.
I'm towing my 40' trailer with a Chevy dually now (8.1 gas, 4.10 gear) and it has more than enough power but could use 200-300 more rpm to be absolutely perfect on the highway. I like to run 68-69 mph (we're still 65mph for the most part back east) but the truck likes 75 mph way better. I can actually hold speed on grades at 75 that bog me down at 65-70. Anyway, I did the math and the new truck has a 5.57 gear and low pro 22.5 tires, and it comes out to right at 200-300 rpm more than I am pulling in my current truck, so it should work out perfect in theory. That is figuring from each trucks 1:1 gear, 5th out of 6 on the dually and 4th out of 5 on the allison in the 6500. Same 8.1 gas motor in both. Plus we drove the truck home from Wisconsin to eastern Ohio and it'll hum along nicely at 75 in overdrive without straining the engine. So I think I am good. Excellent advice though, I have seen other guys on the forum fighting gearing issues. And you are right, it is sure easier to change out the pumpkin when I can just back the chassis under the shop hoist instead of manhandling it on a creeper. That is the one problem I can see with your truck, I pity the guy that has to work on the drivetrain when something breaks. You're gonna need one of those old fashioned semi shops with a pit to do any work under there. I think I'd have built a taller garage instead. lol. It was a Schwann's truck, so I guess they must do more country miles than city so the gear the trucks differently than a ordinary delivery truck.
I know all you diesel guys are cringing at my choice of a gas motor, but I think I am going to be fine. Pulling the same trailer right now with the same motor in my dually, with power to spare. I can pass semi's up a grade all day long. I know the 6500 is heavier, but I figure between the extra power I have now and the better gearing I should be just right to pace the big trucks, and I'm not generally in a hurry anyway. Couldn't pass up the deal on the chassis. 2003 GMC 6500 in real nice shape and reasonable miles for $4800. Ex Schwann's ice cream truck, so it runs on propane which is not a big deal here as our family business was propane and we have run countless vehicles on propane over the years. Great for engine life, runs like brand new. I can hold 160 gallons of propane, so won't have to fill up often and every Flying J has it, generally a little cheaper than gasoline.
Once again, thanks for the advice.
Dave
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