Transmission

The Aisin AW55-50SN is a robust 5-speed automatic transmission manufactured in Japan between 1999 and 2014. This transmission is suitable for front-wheel drive and all-wheel drive applications, supporting engines up to 3.5 liters in displacement and a maximum torque output of 330 Nm. It features a total oil capacity of 7.2 liters, with a partial replacement capacity of 3.5 liters, and requires maintenance every 60,000 km. The gearbox has a listed lifespan of approximately 300,000 km. Originally known as the SU1 designation for General Motors, Volvo, and Renault models, this transmission is also recognized in Opel vehicles under the AF23 and AF33 designations. Its gear ratios, exemplified by a 2005 Volvo S40 with a 2.4-liter engine, include a Main ratio of 2.44, 1st gear at 4.66, 2nd at 3.03, 3rd at 1.98, 4th at 1.34, 5th at 1.02, and Reverse at 5.11. This transmission was widely installed across various manufacturers. Notable applications include the Alfa Romeo 166 (2003–2007), Cadillac BLS (2005–2010), Fiat Croma II (2005–2009), Lancia Thesis I (2001–2009), Nissan Altima (2004–2006), Opel Signum (2003–2008), Renault Espace (2002–2013), Saab 9-3 II (2002–2006), Volvo S40 II (2004–2012), and Volvo XC90 I (2002–2006), among many others. While considered robust, early models of the AW55-50SN experienced some issues, particularly with the valve body longevity and potential antifreeze contamination of the lubricant. By 2004, these weaknesses were reportedly addressed, significantly increasing the transmission's service life. At higher mileages, potential concerns include a clogged valve body due to torque converter clutch wear debris and failure of the oil pump bushing, which can lead to leaks.