thatXJguy

So after the several hours of research I've put into regearing, I think I've made the decision to go with 4.56s to compliment my 33s.

So here's the dilemma. I will be taking a trip to New York next summer and need opinions. At freeway speed, would you say I'll get better gas mileage over the 1200 mile (each way) trip with my 3.55s or with the 4.56s? Also, which option is going to put the most strain on my transmission (AW4)? This will ultimately help me decide in whether to regear before the trip or after the trip.

I understand that with deeper gears, the RPMs will be a little higher at higher speeds than they would be with the stock gears. Currently at 60-70 mph the RPMs sit at about 1800-1900. I have read that with 4.56s they might sit at about 2300-2500. I've always thought the higher the RPM the harder the motor is working and that this would mean more fuel consumption, but I read somewhere that that's not always necessarily true in part of my research.

So let's hear your opinions guys, please and thank you!

ZINGGG

You'll definitely be putting more strain on your tranny with 3.55s. I can tell you I see better mileage with my 4.56s than I did with my 3.55s with 33s. By about 3 MPGs. I can't give you the math like others will be able to but you'll be better off all around with 4.56s

Atmos

you're taking a trip to NY a year from now? regear now and buy a plane ticket

andrewmp6

I would fly or if i drove that far it would be a rental car.

kirknd4spd

The 4.56's will be much better all around. Easier on the tranny and engine both. Higher RPMs are much better for the engine than straining at lower RPMs.

thatXJguy

Sorry I need my Jeep up there. I will be there for an extended period of time and a rental car will cost me more in the long run.

thatXJguy

Thanks, that's reassuring

So I've heard, but does anyone know the reason why higher RPMs are better? It seems like it would be making the engine do more work.

DieselD

There was a thread recently where a guy was saying the PCM ran leaner mixtures once you hit around 2500 rpm. Maybe that's why?

Morat

Imagine a graph of Torque/Revs. Ideally you'd have your gears set up so you reach your cruise speed when the revs hit the high point on the torque graph. At that point your engine is most efficient and running at its optimum. You will also be using a smaller proportion of the available torque and power than if you were straining at lower revs to achieve the same output. Your engine is less stressed.

Of course that only works for one specific cruise speed per gear, which is why we've gradually moved from 3 speed autos up to 7 speed autos in an attempt to boost efficiency.

hankthetank

FIFY