Rear differential question

[mrnickleye]

Originally Posted by finaltable

Help me understand this. I read 4.3 rear end as "4.3 rotations of the crankshaft are required to get one rotation of the rear axle" so to get 1000 rpm of the tires the engine (via the transmission) needs to be turning the axle 4300 rpm. The bigger the number is, the greater the torque applied to the wheels but the higher the revs will be when cruising.

Did I get this right?

Yes.
Cost wise, you will NOT by just gears to replace yours. You will find a turbo car pumpkin (the diff) and replace yours with it.

If yo drive 70% or more at hwy speed, then you will get better MPG. If you drive 'mostly' around town, then you will lose MPG, as it will take more gas pedal to get the car moving up to speed.

The NA gears are higher because the HP is lower than turbo car, and is need to get these fat pigs (3700lbs) moving.

Mine gets 17-18mpg town, and 20-22 hwy.

It would be WAY cheaper to put taller tires on the back.

For a year I ran some 255x50x16's on the back. They are 1" taller, and 1" wider than stock.

I got 24mpg hwy on a 1000 mile trip, without loss of 'pickup' around town.