After market Speedometer
 

I’m going with an after market speedometer in my Plymouth. The specs on the new speedo states that 1000 RPM cable input is 60 MPH. Now I’m not sure what the stock MoPar speedo RPM is at 60 MPH but I started doing some math and I would like you guys to take a look and see if I’m on the mark.

Car specs, (1993) A518 trans, 3.91 gears, 27 diameter tire.

Using the info above at 60 MPH driveshaft RPM would be 2919. I need the cable rpm to be 1000 so that’s about 34.2% of driveshaft rpm. (1000 / 2919 = .342)

I THINK the speedo drive gear on the output shaft of a 518 has 13 teeth. Can someone give this an AMEN? (13 / X = 0.342 so X = 38) or a 38 tooth speedometer driven gear.

Does that look correct? And is a 38 tooth speedo gear available?

Th

The factory uses the same 1000 turns per mile calibration so your calculations are correct; you need a 38 tooth pinion.

Thanks John