Second Generation Camaro
Transmission/Drivetrain/Rearend FAQ

  1. Transmission Identification & Decoding

  2. Component Colors (Transmission, Driveshaft, Rear Axle) & Information

  3. Determining rear axle ratio by counting gear teeth

  4. What is a Powerglide transmission?

  5. When was the THM350 transmission first offered?

  6. When was the THM400 transmission first offered?

  7. What were the stock transmission gear ratios for the Muncies?

  8. What is that whining noise coming from my Muncie M22?

  9. What is some transmission trivia?

  10. Can I install a T56 6 speed in my 2nd gen?

Note: See the yearly Camaro information under the "Power Teams" heading for Specific transmission and Rear Axle availability, options, gearing, decoding etc.... for the year camaro you wish to research.

Component Colors (Transmission, Driveshaft, Rear Axle) & Information

  • Transmission - natural aluminum
  • Bellhousing - natural aluminum
  • Transmission Crossmember - semi-gloss black
  • Rear Axle - semi-gloss black
  • Driveshaft - natural steel
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Driveshaft Identification stripes
1970 - 74 (M20,M21,M22) 4 Speed Cars had 2 Stripes. Brown and Light Blue.
1970 - 74 T400 Automatic Cars had 2 Stripes. White and Yellow

The First Stripe is located 6 1/2 inches from the Front of the Driveshaft. This is taken from the Weld mark. The Stripes are 3/4 inches wide and the Light Blue Stripe is first a 3/4" Gap and then the Brown Stripe. This is for a 4 Speed Car.

Q: What is a Powerglide transmission?

A: It was the "base" 2-speed automatic transmission on the small-block Camaros, and very popular. 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.

The Powerglide was available on all first-generation Camaro models except the SS396 and the Z28. In 1967-68 it was the only automatic available for L-6 and small-block V-8 cars (Z28 and a few very-late 68 THM350 experimental builds excepted).

Q: When was the THM350 transmission first offered?

A: The THM350 wasn't officially offered as an option (RPO) until 1969, although some 1968 327/275 Camaros did manage to get this 3-speed automatic transmission as part of an internal GM test fleet. The only way to identify if your 1968 car has an original THM350 is by transmission date code. When the THM350 was released in 1969 it outsold the Powerglide 78,849 units to 66,423. However it was only applied to 6-cylinder and small block V-8 (Z28 excepted) cars, as the high-torque Camaro big-block engines were too powerful for the THM350. The transmission model number comes from the nominal rated torque, 350 lb-ft of torque.


Q: When was the THM400 transmission first offered?

A: The THM400 first appeared on GM passenger cars in 1965. For first-generation Camaro it was only available on, and was the only automatic transmission for, big-block V-8 engines. The model number comes from the nominal transmission torque capacity (400 lb-ft of torque).


  Q: What were the stock transmission gear ratios for the Muncies?

A: Note that the Saginaw 4-speed was also marketed under RPO M20, but with different gear ratios. The Camaro 4-speed manual transmissions, for both Muncie and Saginaw, are as follows:

       Series               Gear Ratios      Input Grooves  Cluster   Output
       (Ratio)   Years  1st  2nd  3rd  4th  Spline (Input)    Pin     Spline
     -----------------------------------------------------------------------
 Muncie M20, M21, M22
     M20 (Wide)  63-65  2.56 1.91 1.48 1.00   10   None    7/8-inch      27
     M20 (Wide)  66-71  2.52 1.88 1.46 1.00   10    2        1-inch      27
     M21 (Close) 63-71  2.20 1.64 1.28 1.00   10    1        1-inch      27
                                                          and 7/8-inch
     M20 (Wide)  71-74  2.52 1.88 1.46 1.00   26    2        1-inch      32
     M21 (Close) 71-74  2.20 1.64 1.28 1.00   26    1        1-inch      32
     M22 (Close) 65-69  2.20 1.64 1.28 1.00   10   None      1-inch      27

 Saginaw M20
     M20 (6-cyl)        3.11 2.20 1.47 1.00
     M20 (V8)           2.54 1.80 1.44 1.00


Q: What is that whining noise coming from my Muncie M22?

A: This noise is normal and has to do with the angle at which the gears mesh. You'll usually hear it in 1st, 2nd, and 3rd gear (but not 4th) after you've accelerated and you then release the gas pedal, letting the engine brake the car. It has almost the same sound in reverse. The M22 gears have a shallower mesh angle which causes the "whine," 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 involved.


Q: What are some transmission trivia?

A: In no particular order, some interesting transmission factoids:


Q: Can I install a T56 6 speed in my 2nd gen?

A: According to Jared Taylor (aka Jetman)

As for a T56 in my 72, it was pretty easy. I bought it connected to an LT1 from a 97 WS6 that was rolled at 3422 miles (kinda makes you feel sick, huh). I thought it was going to take a lot more work than it has, but it was really fairly simple. The car was originally auto, but I had already converted it to a manual. The trans tunnel needed only minor massaging and I had to move the cross member back some. The driveshaft had to be shortened about 2-3 inches. Other than that the only major hurdle was fabricating the brackets for the slave cylinder resivor and such.

Inside the car, the shifter comes up about 2 inches further back. I don't know if it will clear the console or not, I am not going to use one anyway.


Last updated: 10/20/2011
Author: MadMike Maciolek

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