Thread: any insite on the 700R4??

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Well I still think about a 3.70 rear gear with the 700R4 trans. I am farming out the change of my rear gear after Christmas from 2.79 to ? Henry Rifle comments that with the 3.06 low gear in the 700R4 a 3.50 or 3.55 gear should be plenty low enough for acceleration. Then I looked at the site on acceleration:

http://www.alienplanet3.com/hotrodmath/quarter.html

There if I put in 2500 pounds and 260 H.P. at a mere 4200 rpm the program predicts a 1/4 mile time aound 12 seconds and recommends a 3.27 rear gear. Although I know that the laws of Physics can be used in an ideal way to assume perfect traction and predict these times, I do not know the assumptions of the transmission gears in that calculation. Assuming there is only one shift in the 1/4 mile run I would guess my trans would use low (3.06) and second (1.64) gears from a standing start but I have no idea what gear ratios the acceleration calculator uses, so what does the 3.27 rear gear recommendation mean? Interestingly, if the weight of the car goes up to more like that of a Corvette around 3300 pounds the predicted rear gear gets lower. Soooo, the question is, maybe a 3.55 rear gear is too low for a light roadster? Apparently there are a few places which still offer a 3.25 rear gear so that is possible, but then I will not be able to get into OD gear until a higher mph, so maybe after all the 3.55 rear gear is an all around compromise considering that I am using tall tires of 735/75/15? Just wondering while I consider what to tell the guy who will rebuild my 8" rear with a new gear.

Don Shillady
Retired Scientist/teen rodder