Correcting Speedometer

[svtcobra94]

I've got a 904 trans with a 3:91 rear gear. I was wondering what I need to do to correct the speedometer as it is about 20 mph off.

 

[Dfnsmn34]

this should help

http://www.mymopar.com/speedometer.htm


oh...welcome aboard...

Aloha!

 

[68 Sedan]

some, if not all, of those part numbers have been superseded. I just got a 37 tooth gear for "IT", and the number has changed. The gear still has the last two digits of the part number on it, but that is no longer the number of teeth on the gear.

Btw, "IT" has 3.91's and a 27.5" tire

 

[2 Darts]

You should be running a 38 to 41 tooth speedometer gear. The exact gear depends on the wheel/tire package you're using. In general the correction is one tooth per 3 miles per hour.