There is a stamped ratio # on it. Anything above 1.0 will increse speedometer, less will slow it down. i.e. a adapter stamped 0.97 will slow the indicated speed down 3%
BC


BC
1960 Chevy C10 driver 261 T5 4.10 dana 44 power loc
1949 GMC 250 project in waiting
1960 C60 pasture art
Retired GM dealer tech. 1980 - 2022