I've been wondering why my '49 F1 speedometer reads so low and finally I checked the odometer which also reads about 45% low. I discovered my differential is 2.8:1 (or perhaps 2.75:1) while the lowest stock ratios are 3.73 or 3.92. My error is partially offset by running smaller 15" wheels and low profile tires. According to my calculations I can cruise at 69 mph at a comfortable 2500 rpm. This will jump to 74 mph when I go back to stock wheels/tires, if I dare. None of the stock speedometer gear sets come close to compensating for a 2.8:1 differential. Is there any other way of compensating for this? It seems like a small inline gearbox between the speedometer and transmission could, say, double the reading. Does such a thing exist?
Any help is greatly appreciated,
Johann

 

Id say that some of the tranny shops that advertise in the Street Rod and Custom mags should be able to help. Matching all those items up to new speedo gears is something they do on a regular basis.

 

i got a speedometer ratio adapter from UNITED SPEEDOMETER SERVICE in Ca. i cant find the phone no at the time, but if your stuck i'll dig it up tcw

 

[font size="1" color="#FF0000"]LAST EDITED ON 31-Oct-01 AT 01:05 AM (EST)[/font][p]You can look at the speedometer and it might have a calibration adjustment. On my 65 mustang, I just moved this till it was right. Although this wouldn't fix the odometer would it?

 

I found United Speedometer Service on the internet at speedometershop.com. 1-800-877-4798. They sound like they have just the ticket for me. Thanks tcw