Corvette C3 Transmissions
Complete Guide 1968–1982
All manual and automatic transmissions · Exact gear ratios · RPO codes · Production numbers · Popular upgrades
During the Corvette C3 generation, various manual and automatic transmission options were available. Manual transmissions were more popular from 1968 to 1971, after which automatic transmissions were more common. The 1982 model year was exceptional regarding transmissions when only the automatic transmission was used.
Manual transmissions
The Corvette C3 generation offered three- and four-speed manual transmissions made by Saginaw, Muncie, and BorgWarner. Except for a few model years, there was also a wide-ratio or close-ratio version that could be selected from the same transmission.
Saginaw 3-Speed (1968 - 1969)
In 1968 and 1969, the base price of the Corvette included a Saginaw 3-speed manual cast iron transmission. This transmission was not very popular and only a few hundred were produced in 1968 and 1969 as the 4-speed transmission was only available for less than two hundred extra dollars.
| Gear | Ratio |
|---|---|
| 1st | 2.54:1 |
| 2nd | 1.50:1 |
| 3rd | 1.00:1 |
Muncie 4-Speed (1968 - 1974)
The Muncie 4-speed transmission was developed in 1963 for the Corvette and Chevrolet full-size cars. As for the Corvette C3, it was available between 1968 and 1974 in various versions with the codes M20, M21, and M22. It has an aluminum case and weighs 80 lbs. A BorgWarner 4-speed transmission replaced the Muncie starting in mid-1974 on C3 Corvettes.
The M20 is a wide-ratio transmission and was an option in 1968 and 1969 and a standard from 1970 to 1974.
M20 wide-ratio
| Gear | Ratio |
|---|---|
| 1st | 2.56:1 |
| 2nd | 1.91:1 |
| 3rd | 1.48:1 |
| 4th | 1.00:1 |
| R | 3.16:1 |
The M21 and M22 are close-ratio versions, the M22 being heavy-duty, nicknamed the "Rock Crusher", which was only available with the L88 engine.
M21/M22 close-ratio
| Gear | Ratio |
|---|---|
| 1st | 2.20:1 |
| 2nd | 1.64:1 |
| 3rd | 1.28:1 |
| 4th | 1.00:1 |
| R | 2.27:1 |
BorgWarner 4-Speed (1975 - 1981)
The new and strengthened BorgWarner 4-speed transmission was fully introduced on Corvettes beginning in the 1975 model year. Like its predecessor, the gear case is aluminum and weighs 70 lbs. Due to the decrease in engine power triggered by the oil crisis, the heavy-duty M22 version was no longer available.
M20 wide-ratio
| Gear | Ratio |
|---|---|
| 1st | 2.64:1 |
| 2nd | 1.75:1 |
| 3rd | 1.34:1 |
| 4th | 1.00:1 |
| R | 2.55:1 |
The close-ratio M21 was an option on 1975 – 1979 Corvettes, only the wide-ratio transmission was available in 1980 – 1981.
M21 close-ratio
| Gear | Ratio |
|---|---|
| 1st | 2.43:1 |
| 2nd | 1.61:1 |
| 3rd | 1.23:1 |
| 4th | 1.00:1 |
| R | 2.35:1 |
Automatic transmissions
Turbo Hydra-Matic is the name of a family of automatic transmissions made by the Hydra-Matic Division of General Motors. During the Corvette C3 generation, three different TH (Turbo Hydra-Matic) automatic transmissions were available.
TH400 (1968 - 1977)
GM introduced the TH400 in 1964 and it was widely used in other car manufacturers' cars as well. During the Corvette C3 generation, the TH400 was in use between 1968 and 1977 with big blocks and some more powerful small block (L82) versions.
| Gear | Ratio |
|---|---|
| 1st | 2.48:1 |
| 2nd | 1.48:1 |
| 3rd | 1.00:1 |
| R | 2.07:1 |
TH350 (1976 - 1981)
The Turbo Hydra-Matic 350 was released in 1969 and was available in the Corvette C3 generation between 1976 and 1981, after which it was replaced by the TH700R4.
| Gear | Ratio |
|---|---|
| 1st | 2.52:1 |
| 2nd | 1.52:1 |
| 3rd | 1.00:1 |
| R | 2.07:1 |
TH700-R4 (1982)
The TH700R4 was developed and introduced in the 1982 model year Corvette. The stricter fuel consumption and emission requirements drove the development of the TH700R4, which included an overdrive. Thanks to the overdrive, fuel economy improved, and revs at highway speed dropped significantly.
| Gear | Ratio |
|---|---|
| 1st | 3.06:1 |
| 2nd | 1.63:1 |
| 3rd | 1.00:1 |
| 4th | 0.70:1 |
| R | 2.90:1 |
Aftermarket transmissions for Corvette C3
If you do a lot of highway driving and don't care about the originality of your Corvette, a popular upgrade is to replace the transmission with an overdrive. During the Corvette C3 generation, the 1982 TH700-R4 was the only transmission that included this feature.
The installation of an overdrive transmission results in a substantial 30-50% enhancement in fuel economy. Furthermore, it enhances the overall highway driving experience, maintains lower engine operating temperatures, and provides a quieter and smoother ride by reducing noise.
Tremec 5-speed
The Tremec 5-speed transmission is probably the most popular choice and is offered as a kit for the Corvette C3, simplifying the manual car conversion process. With the Tremec 5-speed kit, you can retain your Corvette's existing bolt-on shifter handle, preserving its original appearance. While kits for automatic to manual conversions are also available, they naturally entail more extensive work.
You can read more about these kits on Chevy Hardcore's article and MotorTrend's article.
TH700-R4 and TH200R4
While the TH700R4 became the only transmission option for 1982 Corvettes, it may seem like a viable solution for older models; however, it necessitates additional work. As a result, the more commonly chosen alternative has been to transition to the newer TH200R4 transmission.
The TH200R4 shares the same body size as the TH350 and utilizes the same mounting configuration, allowing for the use of the same driveshaft and cross member. With TH400, you need a little more work, such as a different cross member and drive shaft.
You can browse transmission options from the Corvette C3 options section by model year.
Other Resources
General
- Corvette C3 years
- Corvette Specs, Colors, etc. by year:
1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 - Is the Corvette C3 always a Stingray?
- Corvette C3 charts
- Corvette C3 books
- Mako Shark II
- Corvette L88
- Greenwood Corvettes
- Reader's Wheels: Corvette 1968
- Restomod Corvette C3s
