does anyone make any type of adapter/adjuster for mechanical speedos? So, say when you change rear end ratios, or tire diameters, the "adapter" can be changed or adjusted accordingly... rather than going to a speedometer shop and having the gauge calibrated to the new setup... which more than likely will be changing... or can the speedo's drive at the trans be adjusted somehow? Never really looked at it, just stuck the cable in, and drove away. Seems as though you'd be able to change gears in it's drive??? if so, what's the method of figuring out the right drive ratio for the speedo? until now, been using an electronic pedal-bike speedo (sensor on the front wheel, reads accurately up to 'bout 80mph)... but it would be really cool if the car's speedo read something other than 60mph when it's only going 40... thanks... oh, the main speedo/trans in question: '55 plymouth speedo, '71 727 (for now).
Lots of information here, including DIYS ratio test, gears, and adaptors: http://www.speedometershop.com/rep-pag.htm
The local spedometer shop here just makes a gear adapter that bolts to the transmission. You go in, they screw this thing between your tranny and spedometer cable and you drive a set distance. When you come back, they read the little thing and make a geared adapter that fits between the tranny and spedometer cable. Never heard of adjusting the spedometer to the tranny.
On GM cars you can change the gears in the trans to correct the speedo. Pretty sure you can do the same on other makes. Speedos can be recalibrated but it is expensive for us thrifty guys.
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