1981 Mercedes Benz 300SD mileage: 220,000. I want to change the transmission filter and pan gasket. Because of the mileage and I'm not sure when or if the prior owner changed fluid. I am afraid to have fluid replaced. Present fluid is clear and unburned, should I change it or will someone just change filter and gasket. Second question, vacuum motor in trunk that runs door locks and gas cap cover, quits after about two weeks. If I pull out, disconnect, and then connect three-prong electrical connector, it works for another two weeks. However, I believe that if I disconnect the vacuum line to the motor, it works for unlimited period.
If in doubt, change the transmission filter and gasket and at the same time replace the fluid in the pan. With the transmission pan down, inspect for metallic particles. A slight amount is normal. About your vacuum motor problem, a cracked and leaking vacuum hose probably causes this. Locating and repairing the hoses should fix the problem.