Correct M20 Speedometer Gear?

[1967SS-Dave]

When I bought my 67 it was after a frame off restoration was done. When I got it the rear ratio gears were 4.98:1 !!!! So the first thing I did was put a reasonable drive-able gear set 3.07:1 back in the car and installed a new POSI unit while it was out.  But the speedometer has always been off and slow. At 65mph by the GPS it says I am doing 50mph. As these gears are $20-35 each and there are several of them it could be. I don't want to buy a lot of gears just to sit in a box and unusable. SO this question is. Does anyone know what gear they may have in the transmission to put the speedometer back to a true reading with the same setup I have or "Close"
3.08:1 Ratio26.5" tiresM20 Muncie 4-speed

[Mike S]

Hi Dave,

   I don't know which gear, but I've used a kit sold on eBay to correct the speedometer reading.
https://www.ebay.com/itm/144390409809?chn=ps&norover=1&mkevt=1&mkrid=711-213727-13078-0&mkcid=2&itemid=144390409809&targetid=4580496739019535&device=c&mktype=&googleloc=&poi=&campaignid=603247655&mkgroupid=1230354555785845&rlsatarget=pla-4580496739019535&abcId=9316139&merchantid=51291&msclkid=bf765409aa6b10b802d53c1b89850dcf

Mike

[bcmiller]

Dave,

With GPS showing 65 mph the speedometer shows 50 mph?

Which driven gear are you running now?

I will try to do some checking for you later today.

[bcmiller]

Well I tried. Good luck.

[stormjw]

Found a web site explaining how the calculate speedometer gear for Muncie transmissions. Hope this helps

https://www.cartechbooks.com/blogs/techtips/muncie-speedometer?srsltid=AfmBOoqcrGKcZTpjJ84u9vhnhNlz8WOeFN649qxkHpYIJMXVILNTTLBu