Gearing

Sierra5.3 · May 14, 2002

I am wondering if I change from a 3.73 gear ratio to a 4.10 and run 285's will i be able to get the same gas mileage as i did with the 3.73 and 265's?? or will power just be the same? Thanks

Shaners · May 14, 2002

I don't guarantee you'd get the exact same mpg's, but it should help you out alot, especially for low end torque. That is an expensive mod though...

MarkD · May 14, 2002

I agree with Shaners.

Expensive mod (~$400+ for parts)(~$400 labor). It would take a while to make that back up in gas savings.

I would like to do a similar mod myself though, maybe even 4.56:1!! Our trucks run >2000 rpm at freeway speeds. Usually a 1:1 change in gear will raise rpm 200-400 in OD. The hot gear in Camaro 6-speeds is a 4.11:1 with a 26" tall tire. They don't see huge differences in gas mileage.

A 265/75 is about 31 " tall, and a 285/75 is about 32-32.5" tall so a gear change might be an option.

I will do some math and get back to ya.

96 Vortec · May 15, 2002

I never noticed a dfference in power when I stepped up to my 285's. I did notice a difference in braking.

If you are having trouble with power, I'd add some go fast stuff under the hood.

I wouldn't worry about changing the gears. Especially since you have to change them front and rear so you don't grenade your t-case.

Race18 · June 9, 2003

I did notice a pwr drop when I went to the 285's but it was so little that it doesn't matter. It may be just in my head but I think she takes off slower than with the 265's

ADDZ71 · June 9, 2003

Newbie here - Did you experience a mpg drop going to 285's or just fewer miles on the same gas. Without correcting the odometer for the larger tire you will now read fewer actual miles traveled. Depending on the terrain you travel it is likely that you might have increased your gas mileage i.e. you now have a higher effective final ratio (lower number) than you previously had. Your seat of the pants power probably changed but I can't think that it was too significant from the tires.

Later,

ADDZ71

tyudi5bs · June 21, 2003

I still have my 3.73's in and am running 35" tires. Its killing me, she's slow as a dog and who knows how long the tranny will take the abuse. I can still manage 16 mpg if i really try.

I haven't heard of many people swapping out gears only going to 285's. I guess it just costs too much for the benefit. However, step up to 315's and you almost have to. Most people go with 4.56's running 35" tires. Its actually a little more gear than stock 3.73/265 combo but i know i'll enjoy the increased pep and i never run super fast so i don't have to worry about winding out the engine.

BDBWTE · June 27, 2003

265/75R16 measures 31.6" tall and 10.4" wide.

With this tire you are acheiving you stock gear ration of 3.73..

Now

285/75R16 measures 32.8" tall and 11.2" wide.

With this size tire your synthetic gear ratio will be 3.59:1 which is still pretty good.

High gear would be 3.52:1

Low gear would be 4.22:1

Changing the gears out to 4.10 in your truck..

265/75R16 you will have your 4.10:1 gear

285/75R16 you synthetic gear will be 3.95:1

High gear would be 3.87:1

Low gear would be 4.64:1

Now with all this math done I would leave your 3.73's in the back unless you just like a lower gear but remember you have to match the front to the back and changing that ring and pinion is a lot funner that the back..

Hopes this helps

BDBWTE