Peter Nelson / Jalopnik When the C5-generation Audi RS6 reached American shores solely as a sedan in 2003, it became the first twin-turbo V8 Audi ever. Its Cosworth-built 4.2-liter puts 450 horsepower and 415 pound-feet of torque down to the road through Audi's Quattro all-wheel drive, allowing the RS6 to hit the 60 mph mark in well under five seconds. And despite its portly 4,229-pound curb weight, it was renowned for its hair-raising acceleration and grippy handling. We also can't forget that it's one of our readership's favorite sleepers. However, the Audi RS6 also has several Achilles' heels, as its athletic prowess comes at the cost of a handful of reliability issues. They're rooted in both the big sedan's (and wagon's in other markets) packaging and its complexity. Its suspension and engine have their issues, but what sends the latter's output to the road — its ZF 5HP24A Tiptronic five-speed automatic transmission — is the worst. This automatic is a major concern and requires close attention and care to maintain, or swapping it out for a manual box to either cure or avoid any headaches. The Audi C5 RS6 is a maintenance-heavy car and fixing stuff under its hood is laborious. Be sure to do a lot of research if you're in the market. Dynamic Ride Control and turbocharger issues in the C5 Audi RS6 Peter Nelson / Jalopnik The C5 RS6 may be a big sedan, but space is still at a premium under its sheet metal. Each cylinder head has 20 valves and its own K04 turbocharger with respective piping, water cooling/oiling, intercooling, and two catalytic converters to keep emissions at bay. Then, there's a hulking Quattro all-wheel drive system, four-link front and double-wishbone rear suspension, massive brakes, and hydraulic Dynamic Ride Control (DRC) suspension. Yikes. Let's start with the DRC system. These hydraulically controlled dampers are cool for providing an enhanced driving experience that puts in work restricting pitch and roll yet providing an overall good ride quality (for a sports sedan), but it's prone to problems. Over time, it can sag, leak, get bouncy or too stiff, or start knocking and clunking — these are all signs of DRC system failure. Replacement is a tough and expensive proposition, so many enthusiasts simply ditch it for a conventional aftermarket passive coilover setup. Then there are the turbos, which can wear out over time, especially if the engine oil hasn't been given enough time to warm up before thrashing on it. Excessive intercooler leaks can do them in, too, as can infrequent and/or poor-quality oil changes. Feeling a loss of power, hearing a high-pitched whining (like a dentist drill) or whistling, excessive blue or black smoke from the exhaust, a significant drop in fuel economy, or a boost pressure-related check-engine light can clue one in on them giving up the ghost. Luckily, there are a myriad of sturdy aftermarket replacement options out there. Tips on maintaining a C5 Audi RS6 Audi All C5 RS6s left the factory with ZF's legendary Tiptronic automatic transmission, featuring a lock-up torque converter and shift buttons on the steering wheel. Sadly, no manual option was available because Audi didn't have any other gearbox at the time that could handle such power. Still, they too can develop issues over time, especially with overly aggressive driving or poor maintenance. This is the C5 Audi RS6's biggest Achilles' heel of the lot. Signs of this big ol' box either needing a fluid change, torque converter replacement, or full unit replacement include hard or delayed shifts, torque converter shudder, slipping under acceleration, leaks, grinding and whining noises, or a transmission warning light on the dash. They're sensitive transmissions and need clean, good-quality fluid, at the proper level — and frequent changes. Additionally, go easy on them until the car is up to temperature, just like with the turbos. Sometimes, roughness is solved with a fluid change, but deeper investigation is needed if that doesn't solve it, including replacing the torque converter or rebuilding or replacing the whole transmission. Additionally, swapping to a manual drivetrain from a B5-generation Audi S4 is a popular mod. It's the transmission that the car originally deserved — just ensure that the clutch and replacement box are up to snuff, as they'll be dealing with a lot of power. There are a lot of parts needed, too, but luckily, the internet is flush with knowledge covering what they are.
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