Speedo Gear Help?

[CowBoyRoy81]

Hello,

1971 Dart w/727. I believe 727 came out of a 75 Charger, but not 100%, I do have the original 904 still. I was curious:

Are the speedo gears interchangeable so I could just pull the old one out of the 904 and install into the 727 and get accurate speeds?

If not anyone know the correct sizing to get my speedometer accurate? Factory rear, 3.73 gears I believe....

 

[TrailBeast]

Even the housing is the same between the two.
There are also charts around the net where you put the speed it shows on the speedo now as well as your tire size and rear gear to give the correct gear.
Color of the gear relates to size/teeth of it, so a green gear might be 19 teeth, a yellow gear 16, and so on.
Those examples are not correct but just examples.

 

[Locomotion]

You have to cross-reference the rear end gear ratio and actual rear tire diameter to find the correct speedometer gear. (Gotta know both FOR SURE!) Here is a link to an ad I have which includes the chart. If your existing speedometer gears aren't exactly what you need, then perhaps one of mine will work or you'll know what to look for.

[FOR SALE] - 727/904/833 speedometer pinions & related parts

 

[CowBoyRoy81]

Thanks guys, once I get home I'll measure up the tire height and order up the correct one! Thanks again!