Hello, I think I might have problem with my Automatic Gearbox in my 1992 300E, (with M103 Engine).

After I drive it hard, such as after driving hard in the Highway, and when I park the car, shief in P shift, I heard some noise, which is some high pitch 'e' like noise, and is not continue.

The car drive alright, no problem and kick in sitll work.

I pin point the location, and found that is from the Automatic gearbos oil cooler, as I have a seperate cooler for the gearbox.

I think, the noise is come from the internal bit of the gearbox, then transmit via the oil and the oil pipe. what likely cause the problem? oil pump?

Many Thanks.