Mercedes-AMG GT S C190 Reliability

The 7-speed DCT (Getrag 7DCL750) has a critical internal seal that disintegrates over time, causing the transmission to leak fluid internally. When this occurs, the entire transmission must be removed and opened. Some 2015-2016 owners report being on their 2nd or 3rd transmission. One owner's transmission failed at 26,000 miles with an €18,000 repair bill from Mercedes. There was a recall/service bulletin for 2015-2016 models where transmissions were replaced under warranty. Rebuilt transmissions cost approximately €11,715, new ones €14,940. Many owners report no warning symptoms before sudden failure - the transmission just dumps fluid. Mercedes-Benz Australia issued a recall specifically for this issue. The 2017+ models appear to have improved reliability, but early cars are high risk. If considering a 2015-2016 model, verify transmission replacement history and get extended warranty coverage.

The M178 engine (and related M177) has a timing chain tensioner with a release valve that weakens over time, allowing oil pressure to bleed off when the car sits. This results in a distinctive rattle for 1-30 seconds on cold start, typically occurring between 60,000-100,000 km. If rattle persists for more than a few seconds, the chain, guides, tensioner, and sprockets all need replacing. Mercedes has updated the tensioner part. Labor is expensive due to the engine's dry-sump design and mid-engine placement. Ignoring this warning can lead to chain skip and catastrophic valve/piston contact, resulting in complete engine failure. The chain itself is generally robust (no timing belt to replace), but the tensioner is the weak point. Early detection is key - if you hear rattle lasting more than 2-3 seconds on a cold start, address immediately.

The AMG GT S is rear-wheel drive with 510 hp and 650 Nm of torque going exclusively through the rear wheels. Rear tire wear is inevitable and expensive. OEM tire sizes are 265/35ZR19 front and 295/30ZR20 rear. Michelin spent three years developing the Pilot Sport tires specifically for the AMG GT, using different compounds across the tread sections. Many owners report rear tire replacement every 10,000-12,000 km with spirited driving, or 15,000-20,000 km with conservative driving. Front tires last 2-3 times longer. High-performance tires in these sizes typically cost €350-500 per tire for premium brands (Michelin Pilot Sport 4S, Pirelli P Zero). Budget €800-1,000 per year for rear tires at moderate mileage. Aggressive drivers or track use can wear rear tires in 6,000-8,000 km. Tire rotation is not possible due to staggered fitment. This is an unavoidable cost of ownership for a high-powered rear-drive sports car.

The GT S (especially with AMG DYNAMIC PLUS package) features active engine and transmission mounts that stiffen at higher speeds and in Sport/Race modes for improved handling precision. These are more complex than standard mounts and can fail. Symptoms include dash warning lights (suspension icon), vibration, and the car going into a safe mode where mounts won't stiffen. One owner reported failure after 5 years - it was a wiring harness connectivity issue, not the mount itself, but diagnosis is complex. If one mount fails, the car may disable all active mounts to prevent imbalance. The transaxle design means both engine and transmission mounts are critical for proper drivetrain alignment. Replacement requires specialized tools and knowledge. Cost estimates are based on similar AMG models - the GLS63 AMG engine mount replacement costs €1,758-2,058, and GT S mounts are likely similar or higher due to mid-engine complexity.

The AMG GT S has electronically controlled exhaust flaps that open/close based on driving mode. These flaps can stick closed due to carbon buildup, actuator motor failure, or mechanical seizure from debris. Symptoms include reduced power (boost won't build past 1/3), quieter exhaust note, and sometimes no fault codes. When stuck closed, exhaust gases can't escape properly, preventing turbos from spooling fully. Solutions: 1) Replace actuator motors (€300-400 per side), 2) Clean and lubricate flaps, 3) Physical removal - some specialists cut open mufflers, remove valve mechanism, plug motors back in, and weld up (the car thinks valves work but nothing's there to stick). RENNtech offers an Exhaust Valve Module (€600+) for manual control. The issue is well-known across AMG models with valved exhausts. Most common on cars driven gently or for short trips where carbon accumulates. Using Sport mode regularly helps keep flaps moving and prevents buildup.

Mercedes-Benz has a known electrical system defect affecting various models including 2019-2021 GT-Class vehicles. Control modules (especially signal acquisition module) fail to enter sleep mode, causing excessive parasitic drain when the car is off. This can drain the battery within days, leaving you stranded. Normal parasitic draw should be under 50 milliamps; affected cars draw 2-4 amps continuously. Mercedes knew about this defect as early as 2003 according to NHTSA reports, issued multiple service bulletins, but has not offered a permanent fix. Lawsuits are pending. If your GT S drains batteries regularly despite new battery and alternator, it's likely a faulty control module. Dealers can diagnose which module in under an hour using diagnostic tools. Solution may involve module replacement (€800-1,200) or software updates. Temporary workarounds: disconnect battery when storing, use quality trickle charger (CTEK recommended), or disable certain systems. This is especially problematic on cars that sit for extended periods.

Some AMG GT/GTS owners report small oil leaks from the rear differential/transaxle area. Often not visible unless you remove rear underpaneling. There was a transmission/differential leak recall for certain vehicles - contact Mercedes with your VIN to verify. For cars covered by the service bulletin, dealers replace the entire unit because they're not authorized to service Getrag transaxles in-house - they swap for new/reman unit and return old one to Getrag. The transaxle (transmission + differential combined) costs approximately €16,000 as a complete unit. However, most leaks are minor seal issues that can be addressed for €400-800. Regular differential fluid changes every 30,000-50,000 km can prevent issues. Check for small drops or dampness during inspections. Major failure is rare but catastrophically expensive. Extended warranty coverage is critical for peace of mind on this component.

If your GT S has optional carbon ceramic brakes, they will likely outlast the car under normal driving - easily 100,000+ km, potentially 10x longer than steel rotors. However, when they do need replacement, the cost is extreme: €8,000 for front rotors, €7,250 for rears, plus labor = €15,000-18,000 total. The rotors alone are €3,200 each. Pads are cheaper (€200-400 per axle), but rotors are the concern. Carbon ceramics are ideal for track use (fade-resistant, consistent) but overkill for street driving. Alternative: convert to steel rotors for approximately €1,500 total (Zimmermann fronts + genuine OE rears). Standard steel rotors cost about €1,000 per rotor and last 60,000-80,000 km. For non-track cars, this conversion makes financial sense. Carbon ceramics can also be damaged by improper wheel changes or stone impacts, and damage is usually not repairable. If buying used, verify which brake system the car has and factor this into long-term costs.