Ok, new to all this. Bought a partially finished Model A Roadster with 306 Ford, C4 and 9" Ford rear end. Took a peek inside chunk and it looks like a 2.75/1. Plan to run 29" OD rear tires. Should I plan to change to 4.11 or somthing like that? Also output shaft of transmission and input of rear end are not inline. Chunk input is about 3" to starboard of ******. That a problem? Thanks for your help.
If you go to www.randysringandpinion.com there is a calculator to determine what gear ratio you want. Key in tire size, mph, and it will give you RPM.
Here is another user friendly web page for playing with gears ratios and tire diameters: http://ctny.audiworld.com/mark/s4/gears/gear_calc.html .
I ran 3.00 gears with 30 inch tires for a long time in my roadster. It works really well on the highway, and my car is light enough that the around town performance was OK as well. If you don't plan on long-distance running on the highway, 3.50 to 3.90 gears will give more dig in town. 4.11 gears will give a lot of snap in town, but will make the cruise rpm pretty busy (about 4000 rpm at 80). By the way, my roadster currently has a 3.90 rear gear, 30 inch tires, and an AOD to get great dig around town and long legs at cruise. A good deal all around.
here is a thread on setting pinion angle. If you square the engine with the rear, the side to side off set isnt a problem. http://www.jalopyjournal.com/forum/showthread.php?t=332593&highlight=setting+pinion+angle
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