I rebuilt the vac pump in my 1984 300D. Kit was ~$105, consisting of piston seal (teflon?), 2 inner check valves, and rubber gasket. Does not contain the outer check valve which is integral w/ the fitting. Great vacuum for ~3 years since.

To be safest, replace the 2 bearings in the roller. You can find posts w/ PN's. My 1985 300D came close to shedding parts into the timing belt. My son said it was making a noise. By the time it got home, the bearings had lost all the balls and the arm was cut half thru from dragging on the "roller ramp" for ~120 miles.

I swapped on a replacement vac pump, but didn't receive new bearings ordered from ebay in time. You can get metal-shielded bearings that should contain the balls, but I don't know that the balls are the main threat. In my case, no damage so I expect the balls just rolled past the timing chain. I didn't find any balls on the last oil drain, but hope to next time I pull off the pan. As my case shows, after the bearings go, the arm will eventually cut thru and those steel parts could definitely destroy the timing chain and sprockets. But, without bearings you will hear noises.

BTW, several have tried an electric vacuum pump (VW, Audi, ...). Some say it worked fine, others not. It will run at a higher duty cycle than for its normal brake booster intent, so probably less life than normal.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans