* Capacity and Torque Handling: The 4R55E is the heavier-duty transmission. It's designed to handle significantly more torque than the 4R44E. This makes it suitable for larger, more powerful vehicles.
* Gear Ratios: While both have four forward gears, the gear ratios are different. The 4R55E generally has lower (numerically higher) gear ratios in the lower gears, providing better acceleration, while the 4R44E tends to have taller (numerically lower) ratios, potentially leading to better fuel economy at the expense of acceleration. The exact ratios vary slightly depending on the application year and vehicle.
* Applications: The 4R44E was used in smaller, lighter vehicles, while the 4R55E was found in larger SUVs, trucks, and some cars requiring greater towing capacity or performance.
* Internal Components: Though sharing a similar basic design, internal components like clutches, planetary gear sets, and valve bodies are sized differently to accommodate the torque differences. The 4R55E generally has stronger internals.
In short: think of the 4R44E as a lighter-duty version of the 4R55E. They're related, but not interchangeable without significant issues. Trying to put a 4R44E in a vehicle designed for a 4R55E will likely lead to premature failure.
