Volvo XC90 D5 Oil Leak at Engine-Transmission Interface

To confirm the presence of a leak at the interface, perform a thorough degreasing of the bell housing area. Operate the engine to allow the leak to manifest, then use a bright light to observe the exact point of origin. Distinguish between engine oil (typically dark or black) and transmission fluid (often reddish or brownish) to determine which system is the source.

Sources