Engine Crankshaft Rear Seal BMW M240i 340i 440i 540i X5 X6 B58

The rear main seal is one of the most critical gaskets in the BMW B58 engine, located at the back of the crankshaft where it meets the transmission. Its function is to seal the end of the crankshaft and prevent oil from escaping the crankcase into the bell housing. Due to its location, replacing this seal is a labor-intensive process, making it essential to use a high-quality replacement during any engine or transmission service. Heat, high mileage, and crankcase pressure can cause the original seal to fail, leading to significant oil loss and potential contamination of the clutch or torque converter. This premium seal is engineered to maintain a perfect fit and flexible seal under the intense thermal and rotational stress of BMW's turbocharged straight-six engines.