What the correction number is for the speedo with 3.54 axles on an NP205 transfer case?
3.07 axles use a 1.333 correction box.
My speedo is fast by 10% and the box isn't marked as to what it is.

 

The 3:07 and 3:54 use the same reducer box. A friend of mine has a 3:54 with a getrag. Mine is an auto with 3:07's. We used the reducer box off my truck this spring for a trip in his truck. He had broken his reducer box.

My speedo is correct on MPH. His speedo was correct with my reducer box on his truck.

His reducer box was about 5 MPH fast before it broke.

His reducer box has a .69 marked on it. Mine has a .65

 

I guess I'll have to take it out and hook the VSS direct. Then find a cop that will radar me without being a richard. Then I will know the total offset to correct for.

 

Or have someone follow you for a given distance- say 5 or 10mi. Compare what their odo says to what yours says, and do the math. I would normally just recommend 10mi up interstate, but they probably dont have too many of them up north.

 

rather than call the cops borrow someones Garmin, if you place it off the maps it will give you your exact mph among other things