What month in 1963 did the change over from T-10 to M20 4 speed Muncie Transmission
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Re: 1963 T10 to M20
Probably the beginning of May. It was not an immediate stop/start sequence. There may have been some Muncie's installed and still some T10 close ratios sitting on the shelf. If a 340 or 360 HP car came down the line, they got the T10 close ratio.
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Re: 1963 T10 to M20
Your question makes no sense. M-20 was the RPO code for the 4-speed manual transmission. Whether you got the wide or close ratio gear set was based on engine option. The 250 and 300 HP engines got the WR, and the 340 and 360 HP engines got the CR.
From '57 to late '63 the four speed transmission was the Borg-Warner T-10 design. Beginning in late '63 the T-10 was replaced by a GM design and is referred to as "Muncie" because they were manufactured at a plant located at Muncie, Indiana.
Beginning in 1966 some engines were available with either the wide or close ratio version of the Muncie four-speed. The wide ratio version was coded M-20 and the close ratio version became RPO M-21.
BTW, the difference between the WR and CR is the clutch gear and countershaft, so the 1-2 and 2-3 gear spacing is the same for both. The big difference is the 3-4 intergear ratio - close with the CR and a wide yawning gap with the WR. A better design would be what I call a "progressive ratio" like the current Super T-10s from Richmond gear (also used in the late C3 era) where the gear spacing narrows as you go up through the gears, but that would have required new main shaft gears. Merely changing the counter gear ratio was a cheap alternative.
DukeComment
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Re: 1963 T10 to M20
Danny,
I think I understand what you are asking, maybe! Also the choice of rear gear I believe 4:11 & 4:56 should have been matched with the CR. Maybe the 3:70 also.
The bell housing for the early Muncie installation had the same size front bearing flange, left side speedo gear, and the small cluster gear shaft.
As far as a date, that was answered above.
If you are installing a later model Muncie then the bell housing would need a larger hole for the larger flange and depending on the year, the tail shaft would/could have the speedo on the right side (passenger).
No big deal other than a possible bell housing.
DomComment
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Re: 1963 T10 to M20
I guess my question does makes some sense, From '57 to late '63 the four speed transmission was the Borg-Warner T-10 design. Beginning in late '63 the T-10 was replaced by a GM design and is referred to as "Muncie" because they were manufactured at a plant located at Muncie, Indiana. Thanks Duke and Harry for clearing that up .Comment
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Re: 1963 T10 to M20
Thanks DomComment
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Re: 1963 T10 to M20
To repeat the TIM&JG: "The optional 4 speed transmission was offered in 1963 and 1964. A Borg-Warner unit was installed in 1963 models up to approximately VIN 15000, and a Muncie unit was used for the remainder of 1963 and all of 1964 production." Harry offered the nuances around that timing. They are easy to tell apart.Big Tanks In the High Mountains of New MexicoComment
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Re: 1963 T10 to M20
I have know for a long time that GM changed to the Muncie around the beginning of May.
However, I didn't know the only Muncie available was a wide ratio for the rest of 63.
If I understand this thread correctly the 340 & 360hp cars continued to be shipped with the BW close ratio 4 speed transmissions for the rest of the model year? Did this trend continue for the rest of the HP motors till 1966 or did the specification for the close ratio transmission on the HP cars change? Or did I miss something?Comment
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Re: 1963 T10 to M20
Richard
I think the change over to Muncie included both CR and WR.Comment
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Re: 1963 T10 to M20
Danny,
I was in that era racing and the Muncie was very similar to the Borg Warner design, about a copy that was beefed up with thicker gears and was strong enough to handle the larger flywheels turning bigger tires. hen came the Borg Warner super -10. I believe there were some Saginaw 4 speeds put in GM cars when the Muncie plant burned.
DomComment
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Re: 1963 T10 to M20
Thanks Dom for clearing that upComment
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