Long story short, I want to keep a Fordomatic with my 312 Y Block. The only issue is I have a different rear end than the factory rear end, and I'm having a hell of a time finding the original gear size. The original gearing size is suppose to be 3.31:1. The only one that I can find that even comes close for my differential is 3.25:1. My biggest question is do yall think that this difference will be large enough to make a noticeable difference in the original feel of the car? My only other option is to change from a Ford 9 inch and go to a Ford 8.8. They make the 3.31:1 for that rear end. I just don't like the way they look as compared to that beautiful round behind on the 9.
Tire aspect ratio would make as much difference. Even wear between a new set or tires and a worn set of tires can be around 1%. I would decide what tires you want to fit and do some calculations. You may find that it works out close to identical or if the tires are smaller diameter than stock you may need a higher ratio. Steve
Like he said tire size is also a way of tweaking your concern. I am assuming that all this engine and tranny is going into the same car and not another heavier or lighter car. Let us know how things work out when done...
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