Can a Jetta speedometer with the ratio 1540 be substituted for a Syncro speedometer with the standard 1600 ratio?  If so, will the typical 4% low speed reading be altered to about 8% low, or will it tend to correct to close to an accurate reading?

My rusty math and high school physics concepts suggest to me that if the replacement speedometer had a ratio of 1664, the common 4% low error would be corrected.

(1600-1540) / 1600 = 3.75% fewer revolutions (?)
(1664-1600) / 1600 = 4.00% more revolutions (?)

BTW, does anyone have a spare Syncro speedometer?

Budd Premack
86 Syncro, 88 Wolfsburg
Land of Sky-Blue Waters
Minneapolis, MN