Difference in Speedometers

[67 GTX]

Is there any difference internally with the 150 and 120 mph speedos in a 67, or any year car?

I have both and all of the internals look and measure the same. But, for example, the 60 mph marks are different on both of them. So how do they read correctly?

I don't think there is a different speedo gear calling out a 150 or 120 speedo.
Is the difference in the output shaft for these cars?

 

[68gtxman]

I often wondered this myself! I bought a new white face set of decals in the 150 MPH flavor for my 120 speedo and I figured I would make the adjustment through the speedo gear.

I’ve read that calibration companies adjusted the space between the magnet and the spinning drum inside the speedo head unit to make their adjustments, so try accurately measuring that to see if that is the difference. Then let us know!

 

[Mike67]

Wondered the same thing.... ended up buying a 150 cause I couldn't find an answer...

 

[SDCoronet]

They are not physically different but they are different - I dont remember the details but basically the needle gizmo is magnetized deferentially between the two.

 

[PurpleBeeper]

Wow.....and fyi, I had a 77 Cordoba with a 120mph electronic speedometer. I swapped out a 150mph speedometer from a cop car of roughly the same year & it worked just fine. Plug & play