lets guess on speedo error

[p24-1953]

my hydrive transmission with 3.73 gears and radial tires ran a consistant 10%. (50 in real life showed 55)

i have read that all overdrive were set up for 4.11's so by doing some math i see a 10% difference, so should my speedo be correct or 20% off now?

its late and i cant seem to figure it out?

[greg g]

Why guess load in your gps and take a ride. Gotta throw your tire size in there also.

[Young Ed]

And with either trans there is a speedo gear in there that should be changed for proper diff ratio.

[martybose]

Adding an overdrive would have no effect, because the speedo cable is connected to the tailshaft behind the OD unit. You still need to get 10% reduction gearbox for the speedo cable.

Marty

[p24-1953]

Why guess load in your gps and take a ride. Gotta throw your tire size in there also.

i dont even own a cell phone, why would i have a gps.... i still carry maps.

[p24-1953]

And with either trans there is a speedo gear in there that should be changed for proper diff ratio.

i was thinking that all of george asches transmission were geared for 4.11 gears

[Tony Cipponeri]

When I changed to an overdrive trans, my speedo was off, at 55 miles per hour my speedo was reading 45. Tony C

[Young Ed]

When they were knew they were but that speedo drive is changable. When I put a 3.73 in my 48 I swapped the proper toothed speedo drive gear into the trans and my speedo stayed acurate. My 48 has an amazingly accurate speedo for that old of a car.