RJ, what are we calling stock? I am just trying to figure it out using the 3rd gear ratio of a 730 at 0.875 to 1 and a TC 470 torque converter

**Clifford -**3rd gear in a V-730 has a ratio of 1:1. Not sure why you've included the torque converter, once it's locked up it's not part of the equation.

The bevel gear set is 0.875:1 in this transmission. It's 0.808:1 in the 4-spd manual.

The OEM stock rear axle ratio is 4.125:1.

The

*overall* rear axle ratio is the product of the following math: (High gear ratio) x (bevel gear ratio) x (rear axle ratio) = overall rear axle ratio.

Plugging in the numbers gives you:

(1:1) x (0.875:1) x (4.125:1) =

(1) x (0.875) x (4.125) = 3.609375, or simply 3.61:1

(In the post above yours, I rounded off the bevel gear ratio to 0.87:1, hence the slight difference of 3.588 vs 3.609.)

Either way, it's still a "taller" ratio than the others.

Running the numbers for the manual gearbox and you get an overall ratio of 3.333:1, which, with 500 rpm tires, sends the 4106 down the highway a little over 80 mph @ 2250 rpm. Since it's been said often here and on other Detroit-related websites that 8Vs have be set to 2400 rpm in certain applications, certainly 2250 is not "overspeeding" the engine. Not recommended, obviously. . .

If you really want to go slightly crazy, then we could include installing V-730s in 4905s!

FWIW & HTH. . .