The 700R4 automatic transmission features a 27-spline output shaft. This is a common spline count shared with several other popular General Motors (GM) transmissions and manual gearboxes.
Understanding Transmission Output Shaft Splines
The output shaft of a transmission is a critical component that connects the transmission to the driveshaft, which then transfers power to the vehicle's differential and wheels. Splines are the ridges or teeth on the shaft that interlock with corresponding grooves in the driveshaft yoke, ensuring a secure and efficient transfer of rotational force. The number of splines is a key specification for compatibility when swapping transmissions or replacing driveline components.
Commonality of the 27-Spline Output
The 27-spline output shaft found on the 700R4 is a widely used standard within GM's automotive history, contributing to its versatility and ease of adaptation in various vehicles. This shared spline count simplifies parts interchangeability for builders and enthusiasts.
Transmissions with 27-Spline Output Shafts
Many notable GM transmissions and manual gearboxes utilize the same 27-spline output shaft as the 700R4. This commonality makes it easier to match driveshafts and other driveline components across different vehicle platforms.
| Transmission/Gearbox Type | Output Spline Count | Notes |
|---|---|---|
| GM 700R4 | 27-spline | A popular four-speed automatic overdrive transmission. |
| GM 200-4R | 27-spline | Another four-speed automatic overdrive transmission, often found in lighter-duty applications than the 700R4 but sharing the same spline. |
| GM TH350 | 27-spline | The Turbo-Hydramatic 350, a three-speed automatic transmission, is well-known for its compact size and durability, sharing the same spline count. |
| GM Powerglide | 27-spline | Specifically, the aluminum Powerglide transmission. (Earlier cast-iron versions may differ.) |
| Muncie (Manual) | 27-spline | Various Muncie manual transmissions (e.g., M20, M21, M22) used this spline count for their output shafts, making them compatible with many common GM driveshafts. |
| Tremec T56 (GM) | 27-spline | The GM versions of the Tremec T56 six-speed manual transmission, famously used in performance cars like the Camaro and Firebird, also feature a 27-spline output shaft. (Note: Ford T56 versions typically use a 31-spline output, highlighting the importance of manufacturer-specific details.) |
This widespread adoption of the 27-spline standard means that driveshafts designed for one of these transmissions can often be used with others, provided the overall length and yoke style are compatible. This is particularly beneficial for custom builds and engine/transmission swaps, simplifying the driveline connection.
Practical Considerations for Builders
When undertaking a transmission swap or driveshaft replacement, always verify the spline count of both the transmission output shaft and the driveshaft yoke to ensure a perfect fit. While the 700R4 is primarily known for its 27-spline output, understanding the broader GM spline ecosystem can save time and effort in finding compatible components.
