Spedo cable gear help!

[hawkgoalie31]

I just changed the gears in my rear diff and my spedo cable is way off. I know that you can buy new gears with different teeth can someone please tell me how many teeth I need for the cable to be most accurate.

I have a 1974 Plymouth Duster 318 engine 904 trans 3 speed and a new 8 3/4 rear diff with 3.55s in it. My rear tires size is 245/60/r15

Thanks

 

['64 Cuda]

I think you need a 35 tooth gear. I looked at a chart that said with 3.55 gears and a 26" tire use a 36 tooth gear. For a 27" tire it said to use a 34 tooth gear. My math says your tire should be 26.57" tall so split the difference & get a 35 tooth gear.