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tccrab · 03-20-2024

- The C4 Corvette with ZF6-S40 uses a pulse-signal-reference generated from the Vehicle Speed Sensor (VSS). The VSS, when equipped with a 15 tooth (T) drive gear (on output shaft) and 42T driven gear turning the VSS combined with a 3.45:1 differential ration, produces 4000 pulses per mile traveled. The VSIS is calibrated to 4000 pulses equaling one mile. When the differential (final drive) ratio changes, so does the pulses generated over each mile.
So is possible the VSS plug isn't making good connection or the internal drive gear is damaged or the ECM is fubar.

Crabs

03-20-2024	#2
tccrab Join Date: Oct 2004 Location: Folsom CA Posts: 1,643	Re: Speedometer issue - The C4 Corvette with ZF6-S40 uses a pulse-signal-reference generated from the Vehicle Speed Sensor (VSS). The VSS, when equipped with a 15 tooth (T) drive gear (on output shaft) and 42T driven gear turning the VSS combined with a 3.45:1 differential ration, produces 4000 pulses per mile traveled. The VSIS is calibrated to 4000 pulses equaling one mile. When the differential (final drive) ratio changes, so does the pulses generated over each mile. So is possible the VSS plug isn't making good connection or the internal drive gear is damaged or the ECM is fubar. Crabs __________________ TomC '90ZR1 #792 Honorary Pirate [B]If it ain't FUN, you're doing something terribly WRONG. [/B]