i noticed someone on ebay is offering an overdrive gearset made by riverside gear.that will drop 4th gear from 1 to 1.00 ratio to a 13% drop. (that will lower a 3.73 to a final drive ratio of 3.25). it will only fit a m21 muncie with the 2.20 first gear ratio. this way you can keep your orignal muncie and rear gears,and have an overdrive to! and the kit sells for around $385.00 ! that would be a lot easyier and cheaper that the $2700.00 tko600 5speed conversion that i'd been concidering.i emailed the place and they said that these gears are even quieter that the the original gears. this sounds to good to be true. anyone else heard of this or done the conversion ? i'd sure like to know.

Auto Gear Equipment offers the M21Y over drive gear set. You can buy just the gears or a complete new transmission.
http://www.autogear.net/news.htm

Here is a previous thread about this subject:
http://www.chevelles.com/forums/showthread.php?t=122912&highlight=M21Y
Bruce

How's it work? In 4th gear, the input shaft is mechanically locked to the output shaft for 1:1 ratio. I guess they could do this by reversing the positions of 3rd and 4th in the trans and flipping the shift lever. Is that what is going on here? :confused:

How's it work? In 4th gear, the input shaft is mechanically locked to the output shaft for 1:1 ratio. I guess they could do this by reversing the positions of 3rd and 4th in the trans and flipping the shift lever. Is that what is going on here? :confused:

That is exactly what is going on. By the way, Riverside gear doesn't make this set, it is made and designed by Autogear.

Paul

I am still waiting for the rumor to come true and wake up at Christmas and find a Muncie 5 speed that replaces my M22 without cutting up my nice car.