I have a 49 Chevy that i have put a open drive line into but still using the 49 trans STD shift. The rear end is a BOP GM.with a 2:78 ratio. And At 45 MPH on the speed-o the car is travailing at a speed of 65 MPH ( 55 Sec In A Mile ) I under stand that there was only 2 speed-o gears made for the 46 to 54 cars There Rear Ends Were 4:11 And 3:64 Dose Any One Know How I Can Speed The Speed-o Up? Thank For Any All Help That You All Can Steer Me In.
You can buy a ratio adaptor from these guys. http://www.transmissioncenter.net/speedometer_calibration_______va.htm#350
Any speedo calibration shop should have an adaptor to switch the trans gear to make up the huge difference. Using a 350th and a 9" rear, I went from 4:56 to a 2:76.
The simple but not cheapest way would to be to get a speedometer ratio adapter that fastens to the speedometer drive on the side of the trans and the cable fastens to it. It's like a mini quickchange inside so the gears can be swapped to correct the speed that the cable is driven at. It looks like several of us posted at the same time. You would have to figure out the percentage that the speedometer is now off and change the ratio by that percentage. They are a popular item for 4x4 trucks where guys change rear gear ratios and tire sizes all the time and are used by semi truck shops to correct speedometers on semis. http://www.transmissioncenter.net/speedometer_calibration_______va.htm Scroll down to speedometer ratio adapter.
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