Question about rear gear choice

[nightmare]

I know, I know, another thread about which gear to use with a 700R4. I know most have said to go with a 3.73, but that's with a 28" tire. I've got a 30" tire, and am wondering if a 3.42 wouldn't be a better choice. Right now, I've got 3.08's, and do not like how the gas mileage dropped like a rock.

Does having a longbed adversely affect mileage? I'm just wondering how people are getting 18 to 20 mpg in these trucks.

I'm not expecting that type of mileage, just something more than the 12 I used to get with my TH400.

I've got a longbed with a stock 350, will have a fairly fresh 700R4, and am wanting to choose the right gearing for this combo. I would also like input as to which ring and pinion company (Richmond, Precision, etc.) would be better to use, or which to stay away from. Any thoughts?

[highperf4x4]

If you're running a taller tire then you should go with a lower gear, not a higher one. I would still recommend the 3.73

If you want 18-20 mpg then you'd want to install an lsx motor. Adding overdrive to a gen1 carbureted engine isn't giong to get you there.

[Shaky]

Originally Posted by highperf4x4

If you're running a taller tire then you should go with a lower gear, not a higher one. I would still recommend the 3.73

If you want 18-20 mpg then you'd want to install an lsx motor. Adding overdrive to a gen1 carbureted engine isn't giong to get you there.

+1 on this.

I've used Richmond in the past with good results. That's all I know...

[big_al_71]

I also agree about using a modern fuel injected motor to get near the mpg range you are looking for. I went with 373's and an Auburn posi unit...and I am lucky if I get 8 mpg

[nightmare]

Thanks guys. Any other opinions?

[kwmech]

Originally Posted by highperf4x4

If you're running a taller tire then you should go with a lower gear, not a higher one. I would still recommend the 3.73

If you want 18-20 mpg then you'd want to install an lsx motor.

This..^^^

The 700 has an overdrive ratio of 28%...... going on that premise,

the 3.73 with the 700 is going to give you a final drive of 2.68.

3.73 x .72

[cdowns]

MPG// synthetic oils and grease in engine tranny rear and wheel bearings/front end alingment no slop from worn parts//tires pressures and size//right foot and driving style/ overdrive lockup tranny//lowering for less airflow under truck//efficient intake and exhaust flow//properly timed and tuned engine

those are a few of the most common mileage "secrets"