Gearing with a lift

[08CMAX]

So Ive heard the gearing in the differential is important for power and fuel economy. Can anyone explain this to me and/or tell me if I should be paying to have mine changed. I have an 08 CM 5.7L with a 6" procomp lift...20" wheels and 35s. Thanks in advance!

[08CMAX]

Bump for response!

[jpnca]

This chart may help

4Lo.com :: Gear Ratio & Tire Size Chart

I don't know is an aftermarket ring and pinions are out yet

[djb383]

It's harder for the engine to turn a taller tire with a given gear ratio. The final gear ratio is what gives the engine leverage to turn the wheels. The 4.30 ratio needs to be changed to 4.70, with 35" tires, to give the same mechanical leverage the 4.30 ratio had with stock 32" tires. Even if you could change to a 4.70 ratio, that wouldn't compensate for the extra weight of 20" wheels, the heavier 35" tires and the extra weight of the 6" lift components. With the taller tires and all that extra weight you may need something like a 5.30 (?) ratio to get back to the same mechanical performance as stock.

[08CMAX]

Originally Posted by djb383

It's harder for the engine to turn a taller tire with a given gear ratio. The final gear ratio is what gives the engine leverage to turn the wheels. The 4.30 ratio needs to be changed to 4.70, with 35" tires, to give the same mechanical leverage the 4.30 ratio had with stock 32" tires. Even if you could change to a 4.70 ratio, that wouldn't compensate for the extra weight of 20" wheels, the heavier 35" tires and the extra weight of the 6" lift components. With the taller tires and all that extra weight you may need something like a 5.30 (?) ratio to get back to the same mechanical performance as stock.

Thanks for the reply....are we talking an expensive mod?

[jpnca]

Originally Posted by 08CMAX

Thanks for the reply....are we talking an expensive mod?

Kind of do you have 2WD or 4WD. 4WD is twice the money

[08CMAX]

Originally Posted by jpnca

Kind of do you have 2WD or 4WD. 4WD is twice the money

i have 4wd...maybe they will give me a discount if i promise not to use it

[jpnca]

Originally Posted by 08CMAX

i have 4wd...maybe they will give me a discount if i promise not to use it

Loose the front drive shaft. BAM 2WD

[08CMAX]

Originally Posted by jpnca

Loose the front drive shaft. BAM 2WD

Actually i just hit a low gear with the 5.7L for a wheelie... only using 2 wheels on the ground! LOL

[jpnca]

then maybe you need a turning break

[djb383]

Originally Posted by 08CMAX

Thanks for the reply....are we talking an expensive mod?

Compared to what.........the 20's, the 35's and the lift?

[Deznutjob]

Originally Posted by 08CMAX

Thanks for the reply....are we talking an expensive mod?

My little bro had his 06 4wd Tundra with an 11" lift and 37" tires regeared for $900.

[08CMAX]

What good is my $5k supercharger gonna be without proper $900 gearing! LMAO! Oh well.....I need do it! And yes I said "need!"

[bjowett]

There are no gears available yet... one could speculate some of the Hino light trucks might have some parts that would fit. That will only cover the rear diff, though.

[apimpdad]

Originally Posted by Deznutjob

My little bro had his 06 4wd Tundra with an 11" lift and 37" tires regeared for $900.

$900... is that with the gears and the install? If so thats a pretty good deal.