There Were Many 3-Speed SS's
A Shortcourse On Muncie Transmissions
DC: The guy you talked to is wrong. First of all, my knowledge is mostly with the '68-'72 cars, so that is all I am going to talk about here. You could not get a 3-speed on any COPO-427 cars, or on any 454, ever. It probably wasn't available on the more exotic 396s either (L-78 and L-89). However, you could get a 3-speed on many of the SS-350, SS- 396, and SS-402 cars. In fact, the 3-speed was the base (standard) transmission in the '68-'69 SS-396. In '68, you could get the "M13" HD 3-speed Muncie on the 325 and 350 hp SS-396. Interestingly, you could also get a '68 SS-396 with a Powerglide 2-speed automatic.
In '69, you could get the "MC1" HD 3-speed Muncie on the 325 and 350 hp SS-396. Out of about 71,000 '69 SS-396 Malibu coupes, I would estimate that about 8,000 had the MC1. In '70, the 3-speed manual was not available in any SS cars. However, you could get an "LS-3" big-block 402 in non-SS cars in '70. The base transmission with the LS-3 was the "MC1" HD 3-speed Muncie. In '71 and '72, you could get an SS with the LS-3 402. One of the optional transmissions with the LS-3 in '71-'72 was the MC1.
DC: The MC1 3-speed was the standard transmission on the '69 SS-396. It was also available in '70 through '72 on the LS3 402 big block. The LS3 was not available in a '70 SS. However, the LS3/MC1 combination was available in any non-SS '70 Chevelle/El Camino. I believe that the MC1 was a heavy duty "Muncie". I'm not sure if the M13 3- speed (last used in '68) was a Muncie or Saginaw.
DK: The MC1 HD 3-speed transmission shows up in 1969. Though I can't find any codes for this transmission type, I have a production number of 15,748 out of 503,352 (or 3%). The transmissions with a suffix "A" have 3.03:1 first gear and the "B" suffix transmissions have 2.42:1 first gear.
In 1970 the MC1 was available but not listed in the final 1970 model passenger car option report. Going through the books it looks like the MC1 would have a type code of RR with either an M or an S as the source designation. These would be the first three letters in the transmission code; what would follow after that would be the "date" code. The "M" transmissions are listed as HD truck and the "S" transmissions are listed as LD truck/HD. Passenger gear for this transmission is listed as 3.03:1. I have no production numbers on this year.
In 1971 the MC1 becomes very easy to track. It is designated as a Chevelle-only transmission. Type designations for the Muncie 3-speed in 1971 are R3 for L6 engines and R4 for V8. Here we are only concerned with R4 transmissions as they are the MC1. Total production for this transmission in '71 was 548-all were mated to LS3 402 motors. The engine suffix code for this combination is CLS only. Chevelle-only transmissions have a have a source designation as "H", so an example transmission code would be R4H1XXX, with the X representing a date code, the "1" denotes the model year. As there were 548 total LS3/MC1 cars made, there were a total of 550 made, the left over 2 were used a service replacement engines. The "A" and "B" suffix transmissions have the same gear as described above.
The 1972 MC1 transmission was a rarity as well, the production was a low 286 LS3/MC1 combinations built with 272 making it into cars, the remaining 14 were used as service engines. As with 1971, the only application was the LS3 and the engine suffix is CTH. The sample code for the '71 also applies to the '72 as well but with the model year being changed to a 2 (R4H2XXX). In '71 and '72 there was a passenger Muncie 3-speed as well which would have an S in place of the H and the Truck HD Muncie 3-speed will have an M in place.
SC: An HD 3-speed was made by Muncie in late 1969. These were coded with the letter H on left hand side below the side cover. The casing was cast iron. The early 69 SS used the Saginaw M13. These were coded QPS to indicate a three speed Saginaw, followed by the date code and shift code (either D or N).
RW: 1969 SS 396 Chevelles did come with 3-speed cast iron Muncie transmissions. I had a brand new one in April of 1969. The three speeds were almost bullet proof and would usually out run a 4-speed with the same gearing . Most of the 325 hp cars I saw that were not automatics were 3-speeds, as this was the cheapest way to go, with a 4-speed being a $200.00 option. My car's sticker price was $3280.00.
DM: The 1968 and older Muncies had studs on the side plate that the levers bolted onto. The 1969 and newer had holes that bolts ran into the side plate. There were also two different splines on the input shaft, a fine spline and a thicker spline.
DL: Muncies all begin with the letter "P" on the ID number. The second digit usually stands for the year ("7" would be 1967, so "0" makes me think 1960, although I'm not sure if Muncies were built back then?) There should then be a letter designating the month it was built, then the last two digits, "11" would mean the 11th of the month. Another way to verify it (if it's out of the car) is to look at the input shaft, where the splines are; this is where it gets kindof tricky if you don't know what year the transmission is. Depending on the year/model of the Muncie, there should/should not be a groove or two around the circumference of the input shaft.
All refers to input shaft:
1963-65 M20-10 spline, no grooves
66-71 M20 -10 spline, no grooves
71-74 M20 -26 spline, 2 grooves
63-71 M21 -10 spline, 1 groove
71-74 M21 26 spline, 1 groove
65-69 M22 -10 spline, no grooves
70-74 M22 -26 spline, no grooves
For example, my original 68 Muncie M21 has a 10-spline input shaft with one groove. Another sure-fire way to see if it's an M22 only (M20/21 are the same cut), is to open the 7-bolt side case, and look at the angle of the teeth on the gear. M20/M21 has a 30- degree helical cut on the gears, whereas M22's have a 15-degree cut (this is what makes that "famous" M22 whining sound, or so I hear).
This Tech Article donated by TEAM CHEVELLE