1966 Muncie transmission part numbers?

[Steven S.]

Can someone explain why their is a difference in part numbers between the L79's M21 and L36/72 M21?

Thanks,
Steve

[Tom P.]

Re: 1966 Muncie transmission part numbers?

Very probably because of the difference in the plastic driven speedometer gear.
If two cars have a different rearend gear ratio, ie 3.70 vs 3.36, then the plastic driven speedo gear in the tail housing of the transmission will have a different number of teeth to compensate for the difference in rear gear ratio. Thus, a different part number for the transmission itself.

[Steven S.]

Re: 1966 Muncie transmission part numbers?

That was what I was thinking at first, but I only am seeing one number for L79 and one number for L36/72, no breakdown beyond that.

I'm getting this info from Nolands book.

Steve

[Wayne M.]

Re: 1966 Muncie transmission part numbers?

Very probably because of the difference in the plastic driven speedometer gear.
If two cars have a different rearend gear ratio, ie 3.70 vs 3.36, then the plastic driven speedo gear in the tail housing of the transmission will have a different number of teeth to compensate for the difference in rear gear ratio. Thus, a different part number for the transmission itself.

Well almost, Tom -- actually it's due to difference in the steel drive gear on the output shaft of the trans. There were only 2 varieties (3 if you count a 4.56 ratio). Those two had the same number of teeth (8) but had a different diameter to mate with two "diameter families" of colored plastic driven gears. The latter were added at S.Louis, per the build sheet, and didn't affect the trans part # from Muncie.

A close ratio '66 trans I have that was originally set up for 3.70 or 4.11 final drive ratio has a tag 3880853. I forget offhand what the other number was for the 3.08 thru 3.55 axles. [maybe 3880855]

[Michael H.]

Re: 1966 Muncie transmission part numbers?

Can someone explain why their is a difference in part numbers between the L79's M21 and L36/72 M21?

Thanks,
Steve

Here's a link to a previous discussion that should explain the errors in the AIM and parts books for 4-speed application for 66.

https://www.forums.ncrs.org/showthread.php?t=76058&highlight=3880855&uid=8703

[Steven S.]

Re: 1966 Muncie transmission part numbers?

Here's a link to a previous discussion that should explain the errors in the AIM and parts books for 4-speed application for 66.

https://www.forums.ncrs.org/showthre...80855&uid=8703

Dang, should have been able to find that one with my search... at any rate that more than answers my questions.

Thanks,
Steve

[Ridge K.]

Re: 1966 Muncie transmission part numbers?

I recently started a thread showing the pics of the original restored M21 muncie out of my 43,000 mile '67 400hp.
The tag was still attached to the lower left bolt of the side cover the day we dropped it down, and dusted it off.

Tag stamped 3880853

Car was factory equipped with 4:11 positraction

[Ronald L.]

Re: 1966 Muncie transmission part numbers?

Ridge, you could eat off that trans!