The auto transmission on my 2003 C240 has started slipping lately with 64k miles on the clock. Weak acceleration from low speeds, poor fuel economy and high RPM compared to road speed. I noted about 2500rpm when holding a constant 62mph in fifth which is a bit high. Used to run 2200rpm at that speed. The slipping is obvious when attempting to accelerate, and the trans has a low speed humming sound when it gets hot. Any ideas on where could the problem be ? Many thanks / Ezz