Quote:
Originally Posted by Pontiac1976
Question: these styles of tach if it had 4000 rpm this would have been out of a Disel right.
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Yes, a 4000 rpm tach would be from a diesel. Some diesel tachs use the alternator windings as their signal source, but the diesel tachs used in the 70's/80's medium duty GM trucks were hooked up to a magnetic pickup in the bellhousing that senses the flywheel teeth. As a result, they use a different circuit board (on the back of the tach) as compared to the gas engine tachometers. And the diesel version has calibration jumpers to configure it for the different engine / transmission combos.