I have a M-21 muncie 4 speed out of a 65 442 and want to convert it to a M-20 wide radio. What will need to be done, can I keep the original case? Thanks.

 

Doug has a complete 66 - 67 M20 for sale
5010 case wide ratio
It has a repaired ear Left top

$600 shipped to your door

 

replace the entire trans with one like above, the gears are diff. inside but outside is the same

 

You can change out the input and cluster gear. The input gear runs about $100 and the cluster gear about $150. If you don't want to spend any money see if you can trade straight up for an M20 (unless the case numbers are important to you)

If you switch gears the cluster gear shaft in a 66 & earlier is 7/8" and later years (67 or 68??) go to 1". Just make sure you get the right parts.

I think I have a M20 input gear laying around if you want to cheap out some more.

 

You can put the M-20 guts in yours but I would just change the entire thing and keep the original as it is. An M-20 will bolt in the exact same as the M-21. Where are you located? I have a couple M-20s also.

 

it will be much easier to swap the complete trans. Then you can always switch back to or sell the M21. If you find one close to home you will save about $100 shipping

Good luck with the lds