Semi-Auto gearbox started in the early 2000, with some car manufacturers pushing it as the next generation technology. Designed mainly to fit lower displacement small car, one could also see some higher end vehicles using this type of Automated Clutch Gearbox. Essentially, AMT is a manual gearbox, couple with "robotic" arm and motors to engage and disengage the clutch, effectively shifting the gear automatically for the driver. Since it is a manual box, with its own ECU controlling it, such gearbox can obtain excellent fuel economy, while giving the driver full control of the gear selection when needed in the Manual mode.
Having own a Citroen C3 with Sensodrive, and driving it for almost 12 years now, it's time to share the nightmares with those that are considering a car with this technology. Firstly, an AMT, being a manual gearbox, does not hold the car in drive position while on a slope, it will roll backward! Handbrake control is very important here, as there is no clutch for one to depend on. Secondly, the gear shift speed is at a tortoise speed as the "robotic" clutch need to move in and out to disengage and engage the gear. Most manufacturers learned and went ahead with dual-clutch gearbox years later.
Aside from the operational change of the driver, reliability of such gearbox is a big concern as there are additional moving parts in the system. Whenever things move, failing is imminent. The AMT will usually has two actuators, one the changes gear and another to control the clutch. In addition to that, another component that will fail is the gearbox ECU. The clutch plate maintenance is standard for all manual gearbox as well. Within the first few years of ownership, the gearbox of my AMT has encounter a failure with the clutch actuator, as seen above. The moving arm (where the black rubber enclosing it), refused to move, causing the gearbox stuck at whatever the last gear number it is in. Driving it further in one low gear will cause the gearbox to overheat and give up, thus towing is the only option. Luckily, this was replaced under warranty (Cost about RM3k). Do however note that servicing and maintaining a AMT need special program that connect to the car ECU, to ensure the arm is retracted in a correct position and calibrated precisely. Sending it to those Ah Beng workshop is as well as trashing your gearbox!
Second part that failed was almost 12 years later, which should be considered as worth the praise of the built quality. This round was the Gear Shift Actuator as shown above. This part is expensive, costing about RM5k, and it is heavy and huge, with 2 motors built into it, controlling the gear selection! When this failed, the car either will be stuck at a gear or in neutral, and usually the car could failed while driving, which was what happened to me. With no gear, and in neutral, the car slow down ad stalled! After which the ECU protection came into effect and disallowing it to be driven or started anymore. Both parts are manufactured by SACHS of Germany, thus quality should be high, but with a lifetime!
So, are you still considering a car with AMT gearbox? Think again! If it is without the Hill Start Assist, normal driver will take times to get used to operating on a slope. If things start to fail, pray hard the car is still under warranty. Summary of cost if one were interested:
- Clutch Actuator = RM3,000
- Gear Shift Actuator = RM5,000
- Clutch Maintenance every 80k-120k km = RM3,000
- ECU = unknown, as mine still working
By the way, Citroen has updated my gearbox ECU many times, mostly are safety enhancement. For now, cars in the market with AMT would be and not limited to:
- Greatwall Haval M4 (a lot of pending orders, which it could not deliver and might due to reliability issue of the AMT, start saving money folks!)
- Alfa Romeo Selespeed models where Sime Darby has stop distributing.
- Citroen Sensodrive and EGS models (no longer being sold under Naza, and all Citroen brought in by Naza uses normal torque converter automatic)
- Proton Savvy (where production has stopped)
- Smart ForTwo and Roadster (not available for sales in Malaysia anymore)
