How many Toothed Gear?

[97fxdwg]

I had new gears plus posi put into my rear end recently so of course my speedo is wildly off. All other things being equal (tires,etc.), what should I go with for my gear (19 teeth?) at the tranny changing from stock 2.80 to 3.50's (or was it 3.55's?). Project is a mostly-stock 68 coupe 302 with a 3-speed automatic.
Thanks for the help and sorry for the vague-ness.
:SNSign:

 

[hrspwrjunkie]

There are probably a number of utilities on the internet for this purpose, but this is the only one I can think of off the top of my head: http://www.hanlonmotorsports.com/t5speedo.asp

That should be able to help you with your choice. You will need to know the number of driveteeth on the transmission's mainshaft, but that should be able to help you find what you need.

Ryan

I had new gears plus posi put into my rear end recently so of course my speedo is wildly off. All other things being equal (tires,etc.), what should I go with for my gear (19 teeth?) at the tranny changing from stock 2.80 to 3.50's (or was it 3.55's?). Project is a mostly-stock 68 coupe 302 with a 3-speed automatic.
Thanks for the help and sorry for the vague-ness.
:SNSign:

 

[rbohm]

what size tires are you running?

 

[97fxdwg]

235-60-15's

 

[rbohm]

you need a 20 tooth gear.

 

[67coupe351w]

You were a little unclear as to what your old number of teeth were but if everything else is equal aside from your gear swap and you speedo was accurate before, the easist thing to do is to (3.5/2.8)=(new# teeth /old # teeth) ---> New # teeth = 1.25* Old # teeth. then buy the closest gear availible to this number.

 

[97fxdwg]

Thanks......

Thanks guys - I appreciate the help!

 

[mfp4073]

Those gears used to be fairly cheap and easy to replace. I just bought 4 or so and replaced them and checked them with either another car or one of those roadside "radar checks" (there is one near my house).