The source for all vacuum used is the vacuum pump. It covers vacuum storage, locks, transmission shifting, engine shutdown, power brakes and the air cond controls.

Did you notice a change in how the trans shifted? Maybe a clunk when you come to a stop or a bit harsher shift?

It goes from the pump to the brake booster via a hard line. First thing you need to do is see if there is vacuum in this line while it is running and then see what happens to the level when you turn it off. There is a tee in it to plug a vacuum gage in.

After that point, you need to check the vacuum on each main circuit to see which might have a leak and then go through that circuit finding where the leak is.

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1980 300TD-T (82 Turbo and Trans) 159,000 Miles "Jackie-O"
1983 300SD 272,000 Miles "Aristotle"
1987 Jeep Wagoneer Limited - keeps the MB's off the ice and out of the snow
1994 BMW 530it