Mercedes-AMG GT S C190

The Getrag 7DCL750 dual-clutch transmission is the AMG GT's most expensive weak point. Failures typically manifest as harsh shifting on even-numbered gears, buzzing or grinding from the rear, and dashboard error messages including damper malfunction and differential lock warnings. The transmission may default to odd gears only (1-3-5-7) in limp mode. The root cause is often the electro-hydraulic clutch control unit or internal RPM sensors that cannot be repaired separately. Repair requires complete transaxle removal. Dealer quotes typically range from €8,000 to €12,000 for a rebuild, with full replacement reaching €15,000+. Some owners have reported going through multiple transmissions. The issue tends to appear between 40,000 and 80,000 km, though some cars reach 100,000+ km without trouble. A specialist rebuild rather than dealer replacement can save significantly.

The turbocharger wastegate flappers develop play over time due to the constant back-and-forth movement wearing the pintle and actuator rod. This produces an audible rattle, particularly at low rpm and partial throttle. Initially it is cosmetic but can eventually cause the engine to enter limp mode. Mercedes issued a Technical Service Bulletin (LI09.40-P-061542) addressing this issue. Aftermarket stainless steel wastegate repair kits are available for around €200-400 in parts, with labor around €300-600. If the turbo internals are damaged from prolonged wastegate malfunction, full turbocharger replacement costs €2,500-3,000 per side. A software update to alter wastegate actuation timing is not available for AMG models due to different pressure and actuation conditions.

The oil separator on the M178 engine can fail internally, causing crankcase pressure imbalance and oil leaks around the rear of the engine near the transmission bellhousing. Symptoms include a high-pitched squeak that disappears when the oil filler cap is removed, rough idle, and visible oil around the separator housing. The dry-sump system adds complexity to the repair. The separator itself costs €300-500, but labor is significant due to engine access constraints, bringing total repair to €800-2,000 depending on whether a specialist or dealer performs the work. Typically occurs after 50,000-80,000 km.

The AMG GT S uses electronically controlled adaptive dampers (AMG RIDE CONTROL) that adjust firmness based on the driving mode selected. These units develop oil leaks and reduced damping performance over time, typically between 60,000 and 100,000 km. Symptoms include a noticeably softer or harsher ride on one corner, visible oil weeping on the damper body, and in some cases a damper malfunction warning message. OEM replacement dampers cost approximately €600-800 per unit. With the staggered setup (different front and rear specifications), a full set replacement at a dealer runs €3,000-4,000. Specialist shops can source aftermarket equivalents like Bilstein or KW units at lower cost, reducing total repair to €1,500-2,500.

The performance exhaust system uses electrically operated flap valves that open under load for a more aggressive exhaust note. The actuator contains a coupling spring designed as a sacrificial component that breaks before the motor or flap is damaged. Once failed, the exhaust flap typically sticks in one position. Symptoms include the exhaust remaining permanently loud or quiet regardless of mode selection. Dealer replacement costs €600-1,200 per actuator including programming. Some owners opt to have the flaps welded open or removed entirely as a cheaper alternative, though this affects noise levels and may not pass inspection in some countries.

Like many modern Mercedes models, the AMG GT S has significant parasitic current draw from its numerous electronic control modules that remain in standby mode. The battery can drain flat within 10-14 days if the car is not driven or connected to a trickle charger. This is a characteristic of the car rather than a defect. A quality battery maintainer (CTEK MXS 5.0 or similar, approximately €80) is essential for any AMG GT that is not driven daily. If the battery is repeatedly deep-discharged, the AGM battery will need replacement at €250-500 depending on source.