new dually
Hi i am thinking about ordering a new Denali dually with either a bigfoot camper or northern -lite Question is it better to get a I think a 7.30 or a 4.10 gears for the truck rear end, what is t...
Forum Discussion
Back in the 70's when engines where much less powerful, they needed to run a higher RPM at freeway speeds to tow the load. There is a maximum amount of HP you can get from a engine at any given RPM before the truck decides you want to go faster, and will downshift and increase the RPM and thus HP.
But running higher RPM's means less MPG. So back in the day - I am talking 70's and 80's, having a pickup with 3.73:1 rear axle ratio could tow less than one with 4.10:1 rear axle ratio, and many tow packages came with the 4.10:1 rear axle. With the 4.10:1 running in drive (remember 3 speed transmissions in the 70's and 80's) you would be doing about 3,000 RPM at 65 MPH on the freeway, and the engine was under somewhat light throttle, and able to make more power at that RPM. With a 3.73:1 you could make just at much power, but would run 2,400 RPM and get better mileage.
Nowdays the engine are running much slower, and get better mileage. I would go with whatever rear axle ratio is offered, and let the 6 speed transmission worry about downshifting to 5th gear when you need a little more power. Especially with a slower turning higher torque diesel engine, lower axle ratio is better.
Fred.
But running higher RPM's means less MPG. So back in the day - I am talking 70's and 80's, having a pickup with 3.73:1 rear axle ratio could tow less than one with 4.10:1 rear axle ratio, and many tow packages came with the 4.10:1 rear axle. With the 4.10:1 running in drive (remember 3 speed transmissions in the 70's and 80's) you would be doing about 3,000 RPM at 65 MPH on the freeway, and the engine was under somewhat light throttle, and able to make more power at that RPM. With a 3.73:1 you could make just at much power, but would run 2,400 RPM and get better mileage.
Nowdays the engine are running much slower, and get better mileage. I would go with whatever rear axle ratio is offered, and let the 6 speed transmission worry about downshifting to 5th gear when you need a little more power. Especially with a slower turning higher torque diesel engine, lower axle ratio is better.
Fred.
