How's it goin' fellas!
My problem:I need to know what speedo gear to put in my muncie m-21 to get an accurate reading on my speed.When i take off my hand is showing 10-25mph and that is incorrect.I took out a grey one w/ 22 teeth. My rearend is 3.73 posi 10 bolt and my rear tires are 26in.in diameter. Can anyone advise me on what color gear and tooth count.The speedo gear is 3/4's in diameter.
Any help would be greatly appreciated,thanx.

I know in the Year One catalog they sell speedo gears and they post a formula to figure out what you need. Looks pretty complicated though. I'll send it to you when I get home tonight.

This link might help:
http://www.novaresource.org/speedo.htm

I've emailed Novasource but got no response r they still ALIVE?

You will need a small dia.(1.76") 8 tooth drive gear on the main shaft, and a 23 tooth driven gear...Hope this helps...Crash

My mistake, it's actually in the NPD catalog. The formula is:

Driven gear teeth=(# of drive gear teeth) x (Axle ratio) x (Tire revolutions per mile)/ 1000

Tire revolutions per mile=63360
(Tire outside diameter) x 3.14159

The drive gear inside the trans should have 8,9,18 teeth.

This is on page 73 of their Camaro catalog.

Good luck if you can make any sense out of it.

This formula looks more like chinese checkers but thanx anyway.

I use a mathematical formula to figure speedo gears, all you need is tire dia. and rear end ratio...
F.Y.I. there aren't any 9 or 18 tooth drive gears for Muncie 4-speeds... Large and small dia. 7 and 8 tooth only (6 tooth gears were used but very rare)...Hope this helps...Crash

Hey Crash, how do one checks which one the tranny has inside(7 or 8)?