Heres how the rpms work
Math goes: 70(MPH) x 3.73 (gear ratio) x 336 (given constant) = 87729.6
87729.6/ 35 (tire size) = 2506.56 (this would be the rpm for no OD)
2506.56 x .75 (for 4L80 OD ) = 1880
And it comes out to 2298 @ 70 with 4.56s
Math goes: 70(MPH) x 3.73 (gear ratio) x 336 (given constant) = 87729.6
87729.6/ 35 (tire size) = 2506.56 (this would be the rpm for no OD)
2506.56 x .75 (for 4L80 OD ) = 1880
And it comes out to 2298 @ 70 with 4.56s