The 46RE transmission, often associated with the 47RE due to its electronic control system and OBD2 diagnostics, can present challenges when swapping into older vehicles. A key consideration is compatibility between the transmission’s speed sensor (VSS), the vehicle’s speedometer, and the Powertrain Control Module (PCM). This article will delve into the nuances of 46RE variations and their impact on this compatibility, focusing specifically on the critical speed sensor location.
There are primarily two 46RE versions that can potentially work with your existing PCM. Both feature a speed sensor at the 8 o’clock position on the output shaft, essential for both PCM input and speedometer function.
The crucial difference lies in the speedometer drive. Early 46RE transmissions had both a speed sensor and a mechanical speedometer drive gear at the tail housing. This setup allows for a straightforward adapter use, connecting the transmission output to the original vehicle speedometer cable.
Later 46RE transmissions, however, eliminated the mechanical speedometer drive in favor of an electronic speed signal sent to the PCM, which then communicates with a dashboard speedometer. This difference requires a conversion to integrate the later 46RE into a vehicle with a cable-driven speedometer. This often involves swapping to an early-style tail housing with the mechanical drive provision. This conversion enables both proper speedometer function and PCM control of shift points and torque converter lockup.
Converting a later-style tail housing to an early configuration is a viable option, often involving sourcing a used early tail housing and the necessary gear drive components.
The image above illustrates a later 46RE tail housing, clearly lacking the speedometer drive hole.
Conversely, this image showcases an early 46RE tail housing with both the speed sensor and the mechanical speedometer drive hole.
A third, less common variant exists, primarily found in 2WD diesel applications. This tail housing possesses the casting for both the speed sensor and speedometer drive, but the speed sensor hole is often undrilled and untapped.
Successfully integrating a 46RE into a vehicle swap requires careful consideration of these variations. Identifying the correct 46RE variant and addressing the speedometer drive compatibility is crucial for proper functionality and OBD2 communication. Choosing the right transmission and potentially performing a tail housing conversion will ensure seamless integration with your vehicle’s systems.
