What is the correct spedometer gear and cable

[troy.70R/T]

I have seen some other posts and one even gave me a link to the mopar tech archives but it is not working for me. I need to know how many tooth speedometer gear I need if I have 275/60/15 rear tires and 3:23 gears. From what I can figure it should be a 33 tooth. Where is the best place to get the gear? Also is there any difference between a 4-speed and automatic speedometer cable For a 70 Charger? Thanks

[oldcarnut]

Here's a couple links that may help.  It looks like maybe 30 or 31 teeth by their charts.
http://www.miata.net/garage/tirecalc.html says the tire is 28"

http://www.geocities.com/MotorCity/2398/tires/tire1.htm  These guys put it at 27.98"  This is their chart

Speedometer Pinion Gear Chart
Source: 1972 Dodge FSM

Speedometer Pinion Gear Chart
All Car Lines - All Transmissions
Number of Teeth on Pinion Gear Listed Under Each Axle Ratio.


Tire

Size     2.45  2.71  2.76  2.93  2.94  3.21 3.23  3.54  3.55  3.91  4.10   
27.71     24    26    27    28    28    31    31    34    34    38    39   

28.34            26    26    28    28    30    30    33    33    37    38   

[troy.70R/T]

Thanks for the help and links Oldcarnut. I also figured the tire at 28.00 But do not see any options for that one exactly. If I go with either the 30 or 31 tooth I am about equally as far away from 28.00. So I guess it just depends on if I want my speedometer to read a little fast or a little slow. I wouldn't think it would be off by more than three or four MPH.   Thanks again, Troy

[John_Kunkel]

The math calls for a 30 tooth (actual 30.20). When given a choice of two I always go for the smaller because it makes the speedo read high which helps prevent speeding tickets.

[troy.70R/T]

Ok thanks I will go with the 30 tooth then. any Idea on the best place to order one?

[John_Kunkel]

Most are still available from the dealer, P/N for the 30 tooth is 52068152.

[troy.70R/T]

Thanks for the P# I will check with my local dealer that is if there still there