Have an '83 300SD with high miles (320K), well taken care of, runs very well. I get a high pitch whine above 2500 rpm that is much louder than the normal turbo sound I get from my 1980 300SD, almost sounds like fingernails on a chalkboard. Aside from checking for bearing deterioration by turning the turbo by hand and feeling for rough spots and oil leaks is there anything else to check? I want to take this car on a cross country trip and want to make sure it is good to go.