looking to change my axle ratio

A gear ratio of 2.64:1 means that the pinion shaft turns 2.64 times to turn the ring gear one full turn. A 3.55:1 means that the pinion shaft turns 3.55 times to turn the ring gear one full turn. It does not matter what is driving the pinion, (ratio of the transmission) it will take more HP/torque to turn a 2.64 vs a 3.55 to pull the same effective weight up a grade, or get the weight up to speed.

I'll give you guys the benefit of the doubt that a direct drive transmission with a set of 2.64 gears hauling general freight in the flatlands of the middle of the country might be a very fuel efficient setup, but there are other options in rear gearing and transmissions that are equally as efficient given all other factors are the same.

 

want yer spot on the wall back?

 

You can keep it, I've just been using the parking lot.

 

Your wrong about HP. Your right about torque. Your right, it does take more torqe to turn a 2.64 then a 3.55. BUT, you didn't lose torque in the previous step by running overdrive.

As I have said before, running a 1:1 ratio in trans doesn't reduce torqe. Running a 1:.73 in the trans (OD) you do reduce torqe. Your right, it does take more torqe to turn a 2.64 then a 3.55. BUT, since you didn't lose torqe in the previous step by running od, its a wash. The torqe the motor puts out remains the same, and the final torque to the wheels is about the same.


A/B/C=D
Who cares what A,b&C are as long as they still =D

What if you put hooked up a 2.64 gear set and then added a 1.34 gearset Aside from parasitic loss, that would be the same as if you hooked up a 3.55 by itself.


Using a 1:1 ratio in trans with a 2.64 ratio in rear is close to using a .73 ratio in trans and a 3.55 rear. The part your not getting is that the transmission ratio counteracts the rear end ratio. No one here is suggesting running a 2.64 rear in Overdrive gear on the trans

 

Nope and nope.

It will actually take slightly less HP at the engine to move the load up the hill with 2.64 in direct compared to 3.55 because there's about 5-8 HP being lost in the overdrive setup through the driveline. That's the whole point of the setup. You cannot neglect transmission ratios, they're just as important as rear end ratios. It just happens that most tranny ratios are very close and have similar ranges, except for direct drives.

A direct drive is the most efficient setup. No torque is going through the countershafts, and the entire driveline behind the output shaft is spinning slower. You cannot spec anything more efficient.

 

Yup this is a very important factor and why most direct drive setups are limited to 80k.

 

At the pinion he's right....at the engine he's wrong. at the wheels he's wrong.

 

If I am right about the pinion, but not at the wheels, how does that work? The pinion turns the ring gear, which turns the axles, which turn the wheels. You can't have your cake and eat it to.

 

View attachment 66680

Give up.....
Freight haulers will never get it, although I will happily let one hook to my trailer and pull a hill anytime they wish.

Martin