On my 72 164, with M 410 transmission, when I put the car in gear right after start up the gears grind. It does this whether I am engaging first or reverse. After a few blocks driving, the grinding starts to dissipate and then after a bit more driving, disappears entirely. I replaced gear box oil about a year ago with Red Line MTL which helped a little. Prior to that it had SAE 30 oil for a year or two and prior to that?????? Clutch is old. In fact my guess is its the original since the car has about 120K miles. What should I suspect and should I do anything about it now or wait until a new clutch is needed. Thanks for all input.