AHS
Senior Member
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Hi all. I'm putting together a ribcase transmission for a 1959 Bygeye that I assume has the original rear gears (I'll check) which if I remember correctly is 4.56:1. This transmission is 1973 vintage which clearly came from a 3.90 ratio car so it struck me that the speedometer gear is probably wrong. This 1973 gear has 13 teeth.
I did some quick calcs and I came up with about 14 teeth is what I need. All the speedometers for Bugeye through at least 1973 are 1472 revs/mile and I believe there is only one worm gear which has 5 teeth. The Bugeye has 145R13 tires which are about 911.2 revolutions per mile.
So 911.2 revs/mile * 4.56 * 5 teeth / 1472 revs/mile = 14.11 teeth needed. If I pull a gear from a smoothcase, will it have 14 teeth?
Oddly with a 3.90 ratio I calculate that 12 teeth would be required, and I know that this 1973 transmission has never previously been apart, yet it has 13! 13 works out well for the 4.22 ratio.
Thanks,
Andy
I did some quick calcs and I came up with about 14 teeth is what I need. All the speedometers for Bugeye through at least 1973 are 1472 revs/mile and I believe there is only one worm gear which has 5 teeth. The Bugeye has 145R13 tires which are about 911.2 revolutions per mile.
So 911.2 revs/mile * 4.56 * 5 teeth / 1472 revs/mile = 14.11 teeth needed. If I pull a gear from a smoothcase, will it have 14 teeth?
Oddly with a 3.90 ratio I calculate that 12 teeth would be required, and I know that this 1973 transmission has never previously been apart, yet it has 13! 13 works out well for the 4.22 ratio.
Thanks,
Andy