1971 replace M21 with 1964-M20

[Robert P.]

Have a change to buy a 1964 Muncie M20.What parts would would I have to Change? Would stock linkage work? Thanks for any help Bob

[Gary R.]

Re: 1971 replace M21 with 1964-M20

I believe your 71 has a fine spline Muncie and the 64 will have a coarse. The counter shaft is smaller on the 64 then the 71. Why do you want to change? The 71 is a better unit unless it's "done"

[Robert P.]

Re: 1971 replace M21 with 1964-M20

I have a 4.11 Diff. I just bought a 3.36, Thinking about putting in a m20 with the 3.36. Driving on the E-way [70+] is murder would like to stay with the muncie. Thanks again for the help

[Gary R.]

Re: 1971 replace M21 with 1964-M20

Ok make sense now. The WR will work better with the 336's. Check both the tranny and diff before you install them.

[Robert P.]

Re: 1971 replace M21 with 1964-M20

Thanks Gray, sounds like It would be better to look for a 71-74 M20. Bob

[William C.]

Re: 1971 replace M21 with 1964-M20

Unfortunately, all the '64 Mincie trans setups used the drivers side takeoff for the speedo gear, and the mainshaft is not setup with the longer register length used on later mainshafts to allow the trans to be built with ether the pass side or drivers side speedo output (location of the drive gear on the mainshaft must be changed) Also, the '71 uses bolt on shift levers, where the '64 is secured with a stud and nut setup. The parts are not directly interchangable as an exterior bolt-on.

[Mark #28455]

Re: 1971 replace M21 with 1964-M20

1971 used a different drive shaft and yoke. In addition, the 1971 design trans is a stronger piece.
Mark