- Gm 3 Speed Manual Transmission
- Chevy 3 Speed Transmission Identification
- 3 Speed Transmission Rebuild
- 3 Speed Transmission Ratios
.The direct drive transmission can be used in both dirt & asphalt race cars.The racing transmission is based on a General Motors Saginaw 3-speed transmission that has a drop out counter shaft in high gear. In an unmodified transmission the input shaft spins the counter shaft and gears all of the time. Assembly of a 3 Speed Manual Transmission (4 bolt sidecover).
| C R G | CRG Reports | Exterior | Engine | 1967 Model ID |
| Numbers Decode | General Info | Interior | Transmission | 1968 Model ID |
| Drivetrain Decode | Options | Underhood | Chassis | 1969 Model ID |
©1998-2021, Camaro Research Group
Edited by and Kurt Sonen// -->
Version: Monday, 22-Mar-2021 13:03:53 EDT
- CRG Research Report:Manual Transmission Floor Shifters
- CRG Research Report:Manual Transmission Bellhousing Alignment
Powerglide Transmission
The Powerglide, RPO M35, was the optional 2-speed automatic transmission for the Camaro. It was available on all first-generation Camaro models except the SS396 and the Z28. It was a popular option in 1967-68 since it was the only automatic available for L6 and small-block V8 cars (Z28 and a few very-late 68 TH350 experimental builds excepted). Its usage decreased significantly with the introduction of the TH350 3-speed automatic in 1969.It is a reliable, smooth transmission and capable of very respectable performance. The Powerglide in 'built' form was the preferred drag-race transmission for quite a few years, and is still popular for drag racing.
In 68-69, there was a low cost version of the Powerglide, RPO MB1, that was marketed as the Torque-Drive. The Torque-Drive had a manual shift valve body and was approximately $100 cheaper than the Powerglide. It was only available with 6-cylinder engines.
TH350 Transmission
The TH350 3-speed automatic transmission wasn't officially offered as an option (RPO) until 1969, although some late 1968 Camaros did receive it as part of an internal GM test fleet. The 68 test fleet cars have unique engine suffix codesand the TH350 should have a date stamp that corresponds to the build date of the car.When the TH350 was released in 1969, it outsold the Powerglide 78,849 units to 66,423. Like the Powerglide, it was only available with 6-cylinder and small block V8 (Z28 excepted) cars, as the Camaro big-block engines had too much torque for the TH350. The transmission model number comes from the nominal torque rating, 350 lb-ft of torque.
TH400 Transmission
The TH400 3-speed automatic transmission first appeared on GM passenger cars in 1965. For first-generation Camaros, it was only available in, and was the onlyautomatic transmission for, big-block V8 engines. In 67 and 68, it was limitedto the L35 325 hp and L34 350 hp engines. In 69, the TH400 was also availablewith the 396 and 427 solid lifter engines. The model numbercomes from the nominal transmission torque capacity, 400 lb-ft oftorque.Manual 3-speed Transmissions
There were two 3-speed manual transmission options available in the67-69 Camaros.The base manual transmission for non-high-performance models and 67-8 SS350'swas the Saginaw 3-speed, M15. If no transmission option was selected, this was the transmission installed. It was column shifted unless a console or RPO M11 floor shift was selected. An exception to this was SS350's, which required the HD 3-speed to get a floor shift.
For 1967-68 SS models, the heavy-duty 3-speed manual transmission, made by Borg-Warner, was available as RPO M13 . For SS350 models, M13 was optional (but was requiredif you wanted a floor shift). For SS396 models, M13 was a required option if another transmission was not ordered.
In 1969, the heavy-duty 3-speed was supplied by Muncie and changed to RPO MC1.It was only available as a floor shift and was available on LM1 and SS models. For the LM1, it was a required option if another transmission was not ordered. For 69 SS models, the HD 3-speed trans was included in the SS package.
Manual 4-speed Transmissions
M20 was the generic RPO for a 4-speed transmission.Gm 3 Speed Manual Transmission
For lower performance applications (L6, 307, 327, and L65 350), the Saginaw 4-speed was utilized. It used a cast iron case.For higher performance applications (LM1 350, SS350, big blocks, and Z28) the Muncie 4-speed was used. It used an aluminum caseand different gear ratios from the Saginaw 4-speed.
The wide-ratio Muncie 4-speed transmission was marketed under RPO M20. The close-ratio version of the Muncie 4-speed was RPO M21 and the heavy-duty close-ratio 4-speed was RPO M22.
The wide-ratio Muncie M20 was available with any of the high-performance engines, except the L78 and Z28 in 67 only came with the M21. The M20 was the only 4-speed available with the SS350 and the SS396/325 hp (L35) engines.
The close-ratio M21 was available only with the SS396/350 hp (L34) engine and the solid lifter engines (Z28, L78, and COPO).
The heavy-duty M22 was limited to just the solid-lifter engines, starting in Camaros in 1968. The Muncie usages are also shown on the ID tables (e.g. the 69 ID table).
The Camaro 4-speed manual transmissions ratios for bothMuncie and Saginaw, with other Muncie data, are as follows:
Muncie 4-speed Identification
To distinguish between Muncie types, if the Muncie was built after 21-Oct-1968, the transmissioncode contains one of three letters at the end of the build code:
A = 2.52:1 Wide Ratio (M20)
B = 2.20:1 Close Ratio (M21)
C = 2.20:1 HD Close Ratio (M22), aka 'Rockcrusher'
The transmission code is normally located on the passenger side of thetransmission, arranged vertically just in front of thetailhousing joint. See the transmissiondecoding information for pictures and more information.
If the input shaft is visible, the number of circumferentialgrooves on the input shaft will also generally indicate theMuncie type. Be careful, as 1963-65 M20 Muncies are likelater M22s in that they have no input shaft grooves. However, the early M20 has only a 7/8-inch diameter clusterpin, while the M22 has a 1-inch pin. Service replacement inputshafts also will have no grooves.
To distinguish an early (pre-suffix) M22 from the otherMuncies when the transmission is on a car, note that allM22s had the lower, forward, passenger-side maincase bossdrilled and tapped for a magnetic drain plug. This wasn'tdone (by the factory) for M20/M21 until 1970. While thisboss could be drilled for a plug on a M20 after it left thefactory - if the boss is undrilled, then the case definitelywas not part of a M22.
The M22 gears have a shallower mesh angle to reduce thrustload and heat. If the gearbox cover is removed, thedifference in the angle between the M22 gears and the gearangle used in the other Muncies is discernable. Note in thephoto below that on the M20/M21 the bottom of the next toothstarts below the top of the preceding tooth (i.e.,they overlap), whereas on the M22 the angle is such that theteeth actually have a small gap between the top of one toothand the bottom of the next.
The shallower mesh angle of the M22 causes a 'whine' noise in 1st, 2nd, and 3rd gears and the sound is the reason for the popular nickname for this transmission, the 'Rockcrusher.' The lower angleincreases the load carrying capacity of the gears at theexpense of the increased noise. The reason for absence ofthe noise in 4th gear is that 4th is a direct output fromthe input (1:1 ratio), and there are no significant gearsinvolved.
For additional details on other transmission componentcasting numbers, component casting dates, and internaltransmission details, see Colvin's Chevrolet By The Numbersseries, listed in the CRGReferences.
Shifters - Manual Transmission
See the Manual Transmission Floor Shifters article for detailed shifter information.All 1967-69 Camaro 3-speed transmissions transmissions used Muncie shifters. 1967-68 Camaro 4-speed transmissions (Saginawtransmissions as well as Muncie) also used Muncie shifters.
The stock Muncie shifter was mounted by a bracket to the transmission crossmember and further supported by a longitudinal stabilizer. This caused problems in performance applications due to the transmission twisting under load and binding the shifter levers - causing many a missed shift.The stock Muncie 4-speed shifter was often replaced by the aftermarket Hurst Competition-Plus shifter. The Hurst shifter mounts directly to the transmission housing, instead of the transmission crossmember, which eliminates the shifter binding issue.The 67-68 Hurst aftermarket bracket used U-bolt around the tailhousing.
The Muncie shifter in 1967 was generally stamped 'MUNCIE' on the handle, thoughsome shifters have unmarked handles.
The Muncie shifter on the Saginaw was not stamped, while the Muncie shifter on the Muncie transmission was generally stamped 'MUNCIE'. There are known exceptions to this rule though.
1969 Camaro 4-speed transmissions (Saginaw and Muncie transmissions) used a factory installed Hurst shifter. The Saginaw transmission required different shift rods than the Muncie and the Muncie small block rods were different than the big block rods. The factory Hurst shifter was similar to the over-the-counter Hurst Competition-Plus model, but differed in the following ways:
- Slip-in 'bayonet' style round handle (stamped 5325) instead of bolt-on square handle.
- No adjustment stop bolts.
- OEM 69 shifters used molded rubber bushings for the rod ends. Aftermarket Hurstshifters used nylon or bronze bushings. Rebuilt or reproduction shifters use the 1970+rubber insert bushings.
- Small-block and big-block cars each used unique shifter mounting platesbolted to the tailhousing. The aftermarket Hurst bracket bolted to the tailhousing, but was the same for both small-block and big-block.
Shifter Knobs
- 1967
- All shifter knobs were a 2-piece ball: the top 2/3 wasblack, with the shift pattern printed in white; the bottom1/3 was chromed and included a threaded locking ring.
- 1968 and 1969
- With a console, the shifter knob was a chrome ballwithout a pattern. Without the console, the shifter knob wasa 2-piece ball: the top 2/3 was black, with the shiftpattern printed in white; the bottom 1/3 was chromed andincluded a threaded locking ring. In 1969 the size of theattach thread was changed from 5/16-inch diameter to 3/8-inchdiameter.
Transmission Crossmembers
The BB manual transmission crossmember looks similar to the SB version, but the BB crossmember opening is squared-off with a beveled corner whereas the SB opening is oval (see picture).The transmission mounting slots for the BB manual trans crossmember are also in a different location than the SB version. The slots are offset about 1/2 inch towards the passenger side and about 3/4 inch forward.
Both crossmembers are mounted such that the two shifter mounting holes (top left holes in the picture) are rearward.
The crossmember used by the 67-68 Firebird looks very similar to the BBcrossmember. It has a squared-off opening with a beveled corner like the the BB crossmember, but the trans mounting slots are centered side-to-side (see sketch).
The 69 Firebird used a one-piece crossmember. It was basicallyjust the upper part of a 67-68 Firebird crossmember (i.e. it is missingthe bottom part with the opening).
The Camaro BB TH400 crossmember is different from the other crossmembers in that it is formed from tubing. The Camaro TH400 crossmember has the mounting plate welded about 1/2 inchoff-center. The Firebird TH400 crossmember is also made from tubing and looks very similar, but the mounting plate is centered.
Service Engine and Transmission Identification
Quoting from the Chevrolet Dealer Service Information Bulletin, 69-I-1,dated 19 Sept, 1968:
The following system will be used to identify service engine and transmission assemblies* including replacement parts. Manufacturingplants will number each assembly as it is produced. The first letter will designate the GM division which produced theengine. |
Most service parts were produced specifically for service.Production engines and transmissions were generally not used as service parts.
Transmission Trivia
Chevy 3 Speed Transmission Identification
In no particular order, some interesting transmission factoids:- The M20 4-speed, standard transmission, RPO was a generic category. It wastranslated at the factory into a low-performance Saginaw when teamed with the L6engine, as the higher-performance Saginaw in the lower-end V8s, and as a Munciein higher-performance V8s such as in the SS and Z28 models.
The line between low-performance and high-performance blurred with time.The 1967-68 275HP L30 engine received the Saginaw while the 1969 255HP LM1 engine received the Muncie. The 250 hp L65 replaced the LM1 mid-year in 69 and it received the Saginaw. - The M40 3-speed, automatic transmission, RPO was also a genericcategory in 1969. It was translated at the factory into the TH350 (actually RPO M38) for non-big-block engines, andinto the TH400 for big-block engines.
- The base 3-speed standard transmission for the SS350 in 1967-68was the 3-speed, column-shift, Saginaw. And it was only available inthe column-shift. If a floor-shifted 3-speed was desired, the M13 HDthree-speed, available only in floor-shift, was a separate option. Thebase SS350 (and LM1) 3-speed was changed to the floor-shifted HDversion in 1969 - the column shift standard transmission was no longeravailable in the SS or LM1 cars.
- The HD three-speed standard transmission was RPO M13 in 1967-68(manufactured by Borg-Warner), but was MC1 (manufactured by Muncie) in1969.
- A floor-shifter for automatic transmissions was only availablewith the D55 console. Except 1968 L35/L34 396 engineswith the TH400 transmission, for which a non-console M11floor-shifter was available (it looks somewhat like the Mustangauto floor shifter).
- The MB1 'Torque-Drive' two-speed transmission was only availablefor the L6 engines, and only in 68-69.
3 Speed Transmission Rebuild
3 Speed Transmission Ratios
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