Hot Rods Muncie 4-Speed Experts?

I've got an M-20 and have decoded the case. Was just curious if anyone knew why the stamped ID date code would be XXX'd out. Looks it may be a 1967 (P7?05) case, not sure what it came out of but has been sitting on a shelf in the garage for 40+ years. I've got an M-21 a well with same case casting but the stamping is still good (P0427) so should be built April, 27 of either 1965 or 1966.

 

Looks like someone who didn’t know better did it. I don’t think factory. Does it have the smaller countershaft?

 

It's a 1967 Muncie with a 1" pin. I agree the Xs are not factory..but you can still see the assembly date as P7M05..which is August 5th of 1966 for a 1967 model year car. If you look to the right of that...see the cast in number 4 with the 4 dots underneath? That means the case was cast in April..4 dots equal 4th week.

 

I thought the 1” shaft did not come out until late 68, early 69?

 

It was probably stolen at some time and someone tried to get rid of identifying numbers.

 

Maybe it was built from parts and the number no longer mattered.

 

At this point ,most are built from parts ,numbers never really did matter .

 

65/66.

 

The Muncie with case ending in 704 (1963) and 325 (1964-1965) was the last 7/8ths pin. The transmissions with cases ending in 010 (1966-1967) 660 (1968-1969) 661 (1970-74) are all 1" cases. So first 1" pin case was 1966.

 

The much less desirable or reliable 7/8 countershaft pin trans was made from 63-65. Most easily identified by the last 3 numbers in the casting number near the top of passenger side. The numbers are 325. They are not as strong as later transmissions. GM realized that and upgraded the transmission to a 1 " pin from 66 until the end of production. After way too much trouble with the 325 cases I avoid them like the plague. Use them ONLY for concourse restorations.

 

Still better than a Saginaw!

 

Thanks for info. Not concerned with numbers matching, but was curious as to why they were XXX'd out. Thought maybe it meant a rebuild or ???

 

Numbers really don't mean much ,I know of at least a dozen 7/8" pin cases with 1" pins .More that started out as wide ratio that are now close ratio , etc , etc. We used to get them @ the junkyard for $25 , take the best parts & make a good trans out of them .

 

Thanks guys I learned a little something today. I only had one small shaft trans. When I turned it into an s I went to the 1”.

 

Denny, I would beg to differ. When my 325 7/8 pin Muncie took its final BIG dump, I put a Saginaw in just to use until I could find a 1" Muncie. That transmission would occasionally pop out of 3rd and I was to lazy to rebuild it. I found another Saginaw and installed it. That was about 25 years ago and it is still in my El Camino. It probably has in excess of 250,000 miles on it. I have a moderately warmed over 350 in it and don't particularly drive it easy all the time. The engine is finally wearing out and I plan a heart and lung transplant of a destroked 400 and a world class T5 from an 89 IROC Z. The Saginaw will find a home in the garage until I, or somebody else needs it.

 

Just stirring that old pot, was sure I would eventually get a handful of people singing praise on them, I guess if people know the history of the Saginaw and understand the transmissions' limits they work just fine.
I've never had one, many Muncies though, I did replace the three speed in my 57 BelAire about 1970 with a B-W T-10.
I do recall a number of guys back in my high days that replaced their grenaded Sags with Muncies, no doubt self induced knowing those guys.