The 2006 Mercury Mountaineer uses Ford’s 5-speed automatic transmission from the 5R55 family. Two-wheel-drive models typically use the 5R55S, while all-wheel-drive models use the 5R55W. The transmissions are paired with the year’s engine options, the 4.0-liter V6 and the 4.6-liter V8.
To clarify which unit your Mountaineer has, consider its drivetrain: rear-wheel drive or four-wheel drive, and the engine under the hood. Below is a concise look at the two main transmission variants used in 2006 Mountaineers.
Transmission variants by drivetrain
The Mountaineer’s 5-speed automatic transmissions are part of Ford’s 5R55 family. Here are the two primary variants you’ll encounter in the 2006 model year:
- 5R55S — 5-speed automatic used primarily on two-wheel-drive Mountaineers with engines such as the 4.0L V6 and 4.6L V8; features standard overdrive and electronic controls.
- 5R55W — 5-speed automatic used on all-wheel-drive Mountaineers; compatible with the same engines but includes AWD transfer-case integration and related torque management.
In practice, if your 2006 Mountaineer is RWD, you’re most likely looking at a 5R55S; if it’s AWD, the unit is typically the 5R55W. The two transmissions share many internal components but differ in their AWD/torque-management interfaces.
Engines and transmission pairing
The 2006 Mountaineer offered two main engine choices: 4.0-liter SOHC V6 and a 4.6-liter OHV V8. Both engine options were commonly mated to the 5-speed automatic transmissions described above; no manual transmission was offered that model year for Mountaineer.
Summary
In short, a 2006 Mercury Mountaineer uses Ford’s 5-speed automatic transmission from the 5R55 family: 5R55S for rear-wheel-drive and 5R55W for all-wheel-drive configurations. This pairing remained consistent across the available engines that year, providing familiar shifts and torque handling for the Mountaineer’s drivetrain.