What design is the 55-65 3sp transmission?

[Tom P.]

There seems to be a fair amount of debate as to the design of the 55-65 (as well as 54-earlier) 3sp transmissions. Some sources show it to be a Saginaw 3sp design, some show it to be a Muncie 3sp design.
For MANY years I've always know it to be the early Saginaw design, but there seems to be a strong belief that it was a Muncie design.
Who knows?????

[Marco H.]

Re: What design is the 55-65 3sp transmission?

Tom,
Per Alan Colvin's Corvette By The Numbers Book - All 55-69 3 Speed transmissions were made in Saginaw. There were design changes, making the later transmissions 'appear' more like Muncies.
Marco

[Joseph L.]

Re: What design is the 55-65 3sp transmission?

The confusion lies in the difference in the casting and manufacturing location, and the design type of the transmission: Muncie design vs. Saginaw design. This is specifically for the 4 bolt side cover transmissions with a non-synchronized first gear.

All Corvette 3-speeds were cast in Saginaw along with main cases for 3-speeds of other uses. Transmissions were also cast in Tonawanda. One can tell the difference by Saginaw date cast transmissions have single digit year. This is from the judging manual.
The 3-speeds were manufactured/ assembled in Saginaw. You can see the "S" followed by the month and date stamped into the main case representing the manufacturing date. This again is from the judging manual.

The 1955 passenger car shop manual, transmission section does not provide any information. The GM truck overhaul manual (Corporation Model SM318 3-speed), has the following information in the first paragraph of the manual "The SM318 transmission (Muncie) has a ...."
This basic transmission was used from 1940 to 1966. There are also variations to this including the SM319 that had an overdrive tail assembly.

There was a GM 3-speed Saginaw transmission to not be confused with the earlier GM 3-speeds. It was a fully synchronized transmission for various 1966-early 70's GM applications. The Saginaw design transmission is easily identified by its 7-bolt side cover.

In summary, the Corvette 3-speed transmissions were a Muncie design manufactured in Saginaw.

Joe