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Jim in Wisconsin 03-13-2020 07:39 PM

speedometer gearing

The rear axle in my 33 has "11 - 39" stamped on the flange - a ratio of 3.54 to 1. I replaced the axle many years ago and I think the original was 4.11. (I wonder what the heck I did with that unit? Lost in the shuffle I guess).
My speedometer "turtle" has 18 teeth which I think is not right - it's probably the one from the 4.11 axle. It looks to me like I would need about 21 teeth to get it right.
I've never seen these things advertised as being available - actually it seems like it would be hard to get that large a gear in that turtle anyway.
Any ideas would be appreciated.
Jim S.

Kurt in NJ 03-13-2020 08:43 PM

Re: speedometer gearing

18 tooth is listed in the parts book as for 3:54 ----and lists tire sizes applicable
22 tooth is listed for a lot of 4:11 rears depending on tires

Jim in Wisconsin 03-14-2020 11:36 AM

Re: speedometer gearing

thanks Kurt, it does look like the 18 tooth is supposed to be right. My speedometer sure seems to register too low, something else must be wrong.

Kurt in NJ 03-14-2020 12:55 PM

Re: speedometer gearing

to check the gearing keep track of miles against gps, or mile markers ---this way you know if gearing or speedometer is off ---

JM 35 Sedan 03-15-2020 09:35 AM

Re: speedometer gearing

I have 3.54 gears in my '35 fordor and I'm using a turtle with #18, and it definitely has and 18 tooth gear. Tires are 600x16's. The speedo and odometer are deadnuts on per my two gps's.
If you definitely have an 18 tooth turtle, then I'm thinking your speedo head is causing your problem, or maybe too much friction in your cable.

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