1969 muncie 4-speed questions

[Eric H.]

Re: M-22 Rockcrusher....

For the record, the "gear" which is integral to the input is not first or forth gear. It is the gear which drives the counter shaft, enabling the transmission to have first, second, and third "gearing". In fourth gear,the input shaft is directly coupled to the main shaft, one to one. In fourth gear, no power is transmitted through any of the gearing. They're all just there spinning.

Sorry to jump in, but I just completed a rebuild of my M-20.

Regards.

[Joe L.]

Re: M-22 Rockcrusher....

Ric------

So, which gear is fourth gear, then?

[Joe L.]

Re: 1969 muncie 4-speed questions

Scott----

If the input shaft has 2 circumferential grooves on it, the transmission IS an M-20 (2.52:1 low gear). If an input has NO grooves on it, then it's really uncertain what the transmission is for the reasons that I described earlier. However, if the input has 1 groove (M-21) or 2 groove (M-20) there is NO uncertainty about which transmission it is. Unless, of course, some "joker" cut the extra grooves into the input shaft in order to fool someone into thinking that they were getting an M-20 when the transmission was actually an M-21 or M-22.

[Eric H.]

Re: M-22 Rockcrusher....

Joe -

Oh where, oh where has my fourth gear gone!!! It was there last time I shifted!

When you shift to fourth, the front clutch pack on the main shaft couples directly with the input shaft. The transmission then becomes a straight through metal bar. No gearing is involved. Since no power is being transfered gear to gear, much of the gear noise should go away.

This is probably where the name "four speed" came from, rather than "three speeds and a locked shaft" !!!!!

The M-20 is the wide ratio, right??

Ric

[scott dixon]

Re: 1969 muncie 4-speed questions

so why does my build sheet say "close ratio 4 speed"?

[Joe L.]

Re: M-22 Rockcrusher....

Ric-----

You're absolutely correct about the power transfer through the transmission in fourth gear. However, if one were to "call" one part of the transmission "fourth" gear, which part would that be? Remember, now, which part that the 3-4 synchro engages when the transmission is shifted into fourth gear.

The M-20 is, indeed, the wide ratio. However, that RPO designation really only applies for 66-74 Muncies. For 63-65, all Muncies were designated M-20s but were available in close and wide ratio.

[Joe L.]

Re: 1969 muncie 4-speed questions

Scott-----

I really can't tell you why the build sheet says close ratio although I expect that it's because that's what your car was originally fitted with. It's possible that the gear set in your tansmission was changed. In such a circumstance you could have the original CASE (with the "numbers"), but different innerds. There is also, of course, the possibility that some sort of "funny business" was done with respect to the "numbers" on your transmission.

If you wish to positively verify that what I've told you regarding the grooves is correct, simply remove the side cover. Then, count the teeth on the input shaft gear (the forwardmost gear). You don't need to have any familiarity with gear helix angles to do this. If the transmission is a wide ratio, the gear tooth count will be 21. If it's a close ratio (M-21 or 22), the gear tooth count will be 26.

[Eric H.]

Re: M-22 Rockcrusher....

Joe -

So my 65 M-20 could be either a wide or close ratio? I don't have a groove on the input shaft so it is a wide ratio?

I rebuilt my Muncie about 3 months ago. I looked for fourth gear for two days assuming it had rolled under one of the workbenches!!!!(:>).

Ric

[Wayne M.]

Re: M-22 Rockcrusher....

Ric --- Yes, joe's correct; the double input spline ring to signify wide ratio started with the redesign in '66. So if your '65 trans has none, it's either a wide ratio or one of the extremely rare M22's (which also had no ring, even in '65).

If I were you, I'd keep looking under the workbench for that 4th gear; you might locate it beside the missed shift or the double clutch.