Information on transmission codes and VIN stamps is located on
the drivetrain decoding page.
©1998-2016, Camaro Research Group
and Kurt Sonen
Version: Tuesday, 13-Dec-2016 02:13:45 EST
TH350 & TH400 Transmission Usage
Manual 3-speed Transmissions
Manual 4-speed Transmissions, including gear ratios and ID
Shifters - Manual Transmission
Service Engine and Transmission Identification
ID'ing Transmission via Body Features
CRG Research Report:
Manual Transmission Floor Shifters
CRG Research Report:
Manual Transmission Bellhousing Alignment
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.
The TH350 3-speed automatic transmission wasn't officially offered as an option
(RPO) until 1969, although some late 1968 327/275hp Camaros did receive it as
part of an internal GM test fleet. The 68 test fleet cars have a unique engine suffix
code, EN, and 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.
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 only
automatic transmission for, big-block V8 engines. In 67 and 68, it was limited
to the L35 325 hp and L34 350 hp engines. In 69, the TH400 was also available
with the 396 and 427 solid lifter engines. The model number
comes from the nominal transmission torque capacity, 400 lb-ft of
Manual 3-speed Transmissions
There were two 3-speed manual transmission options available in the
The base manual transmission for non-high-performance models and 67-8 SS350's
was 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.
The heavy-duty 3-speed manual transmission, made by Borg-Warner, was available
as RPO M13 for 67-68 SS models. For SS350 models, M13 was optional (but required
if 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 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.
Maincase Gear Ratios
RPO Years Casting 1st 2nd 3rd Comments
M15 67 3858986 2.85 1.68 1.00 L6 engine
67 3858986 2.54 1.50 1.00 V8 engine
68-69 3925647 2.85 1.68 1.00 L6 engine
68-69 3925647 2.54 1.50 1.00 V8 engine
M13 67-68 T16-1 2.41 1.57* 1.00 * noted as
1.59 in 68
MC1 69 3911982 2.42 1.58 1.00 both castings
3911940 used in 69
Manual 4-speed Transmissions
M20 was the generic RPO for a 4-speed 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 case
and 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 both
Muncie and Saginaw, with other Muncie data, are as follows:
Maincase Gear Ratios Input Grooves Cluster Output
RPO Years Casting 1st 2nd 3rd 4th Spline (Input) Pin Spline
M20 67 3915032 3.11 2.20 1.47 1.00 L6 engine
M20 68-69 3925656 3.11 2.20 1.47 1.00 L6 engine
M20 67 3915032 2.54 1.80 1.44 1.00 V8 engine
M20 68-69 3925656 2.54 1.80 1.44 1.00 V8 engine
M20 63-65 3851325 2.56 1.91 1.48 1.00 10 None 7/8" 27
M20 66-67 3885010 2.52 1.88 1.46 1.00 10 2 1" 27
M20 68-69 3925660# 2.52 1.88 1.46 1.00 10 2 1" 27
M20 70 3925661 2.52 1.88 1.46 1.00 10 2 1" 27
M20 71-74 3925661 2.52 1.88 1.46 1.00 26 2 1" 32
M21 63-65 3851325 2.20 1.64 1.28 1.00 10 1 7/8" 27
M21 66-67 3885010 2.20 1.64 1.28 1.00 10 1 1" 27
M21 68-69 3925660# 2.20 1.64 1.28 1.00 10 1 1" 27
M21 70 3925661 2.20 1.64 1.28 1.00 10 1 1" 27
M21 71-74 3925661 2.20 1.64 1.28 1.00 26 1 1" 32
M22 65 removed 2.20 1.64 1.28 1.00 10 None 1" 27
M22 66-67 3885010 2.20 1.64 1.28 1.00 10 None 1" 27
M22 68-69 3925660# 2.20 1.64 1.28 1.00 10 None 1" 27
M22 70* 3925661 2.20 1.64 1.28 1.00 10 None 1" 27*
M22 71-74 3925661 2.20 1.64 1.28 1.00 26 None 1" 32
# Some late-production 69 Camaros came with Muncie 3925661 maincases.
* The 1970 M22 used in 454 Chevelles used the 1971-74 output shaft.
Muncie 4-speed Identification
To distinguish between Muncie types, if the Muncie was built after
21-Oct-1968, the transmission
code 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 the
transmission, arranged vertically just in front of the
tailhousing joint. See the transmission
decoding information for pictures and more information.
If the input shaft is visible, the number of circumferential
grooves on the input shaft will also generally indicate the
Muncie type. Be careful, as 1963-65 M20 Muncies are like
later M22s in that they have no input shaft grooves. However,
the early M20 has only a 7/8-inch diameter cluster
pin, while the M22 has a 1-inch pin. Service replacement input
shafts also will have no grooves.
To distinguish an early (pre-suffix) M22 from the other
Muncies when the transmission is on a car, note that all
M22s had the lower, forward, passenger-side maincase boss
drilled and tapped for a magnetic drain plug. This wasn't
done (by the factory) for M20/M21 until 1970. While this
boss could be drilled for a plug on a M20 after it left the
factory - if the boss is undrilled, then the case definitely
was not part of a M22.
The M22 gears have a shallower mesh angle to reduce thrust
load and heat. If the gearbox cover is removed, the
difference in the angle between the M22 gears and the gear
angle used in the other Muncies is discernable. Note in the
photo below that on the M20/M21 the bottom of the next tooth
starts below the top of the preceding tooth (i.e.,
they overlap), whereas on the M22 the angle is such that the
teeth actually have a small gap between the top of one tooth
and 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 angle
increases the load carrying capacity of the gears at the
expense of the increased noise. The reason for absence of
the noise in 4th gear is that 4th is a direct output from
the input (1:1 ratio), and there are no significant gears
For additional details on other transmission component
casting numbers, component casting dates, and internal
transmission details, see Colvin's Chevrolet By The Numbers
series, listed in the CRG
Muncie 4-Speed Transmission Gear Angle Comparison
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 (Saginaw
transmissions 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
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, though
some 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 Hurst
shifters 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 plates
bolted to the tailhousing. The aftermarket Hurst bracket bolted to the tailhousing,
but was the same for both small-block and big-block.
- All shifter knobs were a 2-piece ball: the top 2/3 was
black, with the shift pattern printed in white; the bottom
1/3 was chromed and included a threaded locking ring.
- 1968 and 1969
- With a console, the shifter knob was a chrome ball
without a pattern. Without the console, the shifter knob was
a 2-piece ball: the top 2/3 was black, with the shift
pattern printed in white; the bottom 1/3 was chromed and
included a threaded locking ring. In 1969 the size of the
attach thread was changed from 5/16-inch diameter to 3/8-inch
All 1967-69 six-cylinder and small block engines use the same transmission
crossmember. The crossmember opening is oval and the transmission mounting
holes are centered (side to side) on the crossmember.
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.
The crossmember used by the 67-68 Firebird looks very similar to the BB
crossmember. 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 basically
just the upper part of a 67-68 Firebird crossmember (i.e. it is missing
the bottom part with the opening).
The 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 inch
off-center. The Firebird TH400 crossmember is also made from tubing and
looks very similar, but the mounting plate is centered.
SB (top) versus BB (bottom) Crossmember Opening Comparison
Camaro BB vs Firebird Slot Location Comparison
Transmission Crossmembers Offset
67-69 L6 and SB none
67-69 BB manual trans 1/2"
67-69 BB TH400 1/2"
67-69 Firebird none
67-69 Firebird TH400 none
Service Engine and Transmission Identification
Quoting from the Chevrolet Dealer Service Information Bulletin, 69-I-1,
dated 19 Sept, 1968:
Most service parts were produced specifically for service.
Production engines and transmissions were generally not used as service parts.
The following system will be used to identify service engine and
transmission assemblies* including replacement parts. Manufacturing
plants will number each assembly as it is produced.
The first letter will designate the GM division which produced the
K-Cadillac B-Buick P-Pontiac
The second letter will designate the type of unit "E" engine
or "T" transmission. The number following the letter will
designate the model year "9" for 1969. The last five digits
specify the service replacement unit sequence number. The
group of numbers to be used by Chevrolet manufacturing
plants are as follows:
Flint Motor Plant (L6 Engines) 00001 to 19999
80001 to 89999
Flint V8 Engine Plant 20000 to 49999
Tonawanda Motor Plant 50000 to 79999
Example: Number CE900175 designates Chevrolet engine - 1969
year, and the 175th unit produced for service at the Flint
Motor Plant (L6).
Cleveland Transmission Plant 00001 to 14999
Toledo Transmission Plant 15000 to 24999
Saginaw Transmission Plant 25000 to 34999
Muncie Transmission Plant 35000 to 44999
Hydra-Matic transmissions will be numbered with the letter "H"
regardless of the G.M. Division using the transmission.
* This numbering system applies to service engine assemblies,
partial engines, fitted cylinder cases, cylinder cases,
transmission assemblies and transmission cases.
In no particular order, some interesting transmission factoids:
- The M20 4-speed, standard transmission, RPO was a generic category. It was
translated at the factory into a low-performance Saginaw when teamed with the L6
engine, as the higher-performance Saginaw in the lower-end V8s, and as a Muncie
in 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 generic
category in 1969. It was translated at the factory into the
TH350 (actually RPO M38) for non-big-block engines, and
into the TH400 for big-block engines.
- The base 3-speed standard transmission for the SS350 in 1967-68
was the 3-speed, column-shift, Saginaw. And it was only available in
the column-shift. If a floor-shifted 3-speed was desired, the M13 HD
three-speed, available only in floor-shift, was a separate option. The
base SS350 (and LM1) 3-speed was changed to the floor-shifted HD
version in 1969 - the column shift standard transmission was no longer
available 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) in
- A floor-shifter for automatic transmissions was only available
with the D55 console. Except 1968 L35/L34 396 engines
with the TH400 transmission, for which a non-console M11
floor-shifter was available (it looks somewhat like the Mustang
auto floor shifter). (Note: the CRG would be interested in
hearing from anyone with a 396/TH400 with a non-console floor shifter.)
- The MB1 "Torque-Drive" two-speed transmission was only available
for the L6 engines, and only in 68-69.