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.

finally figured out what the noise was......The exhaust was replaced years ago and the flexible down pipe from the turbo to the center muffler has a flexible corrugated section that is also wrapped is a metal weave (not factor standard). The corrugated portion of the pipe had a crack which then allowed the exhaust gasses to pass through the weave making lots of high pitched noises..... Took awhile to find this one....