Today’s featured repair is replacement of the transmission hydraulic unit on a 2006 BMW M6.
2006 BMW M6
The 2006 BMW M6 is an awesome car, featuring a V10 engine coupled to a Getrag SMG III semi automatic transmission.
Trying to combine the best of both worlds this transmission has a clutch but no clutch pedal and has no conventional standard transmission gearshifter. You can choose to shift it yourself by moving a shifter handle or clicking paddle shifters on the steering wheel. You can also set it to automatic and allow the computer to do the shifting for you.
This all happens compliments of a hydraulic control unit that mounts on the top and side of the transmission. Large solenoids take the place of the shifter handle and the clutch is operated by an electronically controlled hydraulic slave cylinder. All of these components are serviced as a single assembly: when one part breaks, the whole unit must be replaced.
This was the service that was required on our M6. The clutch worked fine but the transmission would not shift gears. As you might guess the hydraulic unit was extremely expensive (many thousands of dollars). We were fortunately able to source a good used unit. Replacement involved removing the transmission which provided access to the hydraulic unit. It was a time consuming job but reasonably straight forward as the hydraulic assembly bolts onto an essentially manual transmission.
After repairs a road test was performed and everything functioned well.
We work on a wide variety of cars and trucks at our shop and always appreciate a road test in a fine high-end sports car. This BMW unfortunately was a huge disappointment. In spite of the 507 horsepower monster engine the car really lacked the get up and go that we expected, and much of that can be attributed to the semi automatic transmission. The delay between shifts really affects the thrill and performance of this car. A regular manual or an automatic transmission would be far superior.
Top and left side view of the semi automatic transmission. The red arrows point to the solenoid unit on top of the transmission. These connect to the transmission shift rods. Yellow arrow points to the clutch slave cylinder & green arrow points to the hydraulic reservoir. These parts are all included with the hydraulic unit.
For more information about the BMW M6 click here https://en.wikipedia.org/wiki/BMW_M6
For more information about semi automatic transmissions click here https://en.wikipedia.org/wiki/Semi-automatic_transmission
