Vintage Cars: 1985 Mercedes 380 SE tranny, vacuum leak, smooth engine

Question
I have a chance to buy this 1985 Mercedes 380 SE with 125000 miles and in great condition, with a smooth engine, but when I shifted into reverse there was a very slight hesitation with a clunk sound and a kick into gear. The same when shifted back into drive. Does it need a transmission replacement? or can the problem be something less expensive?

Answer
providing your tranny has had service done at appropriate intervals , most likely a vacuum leak at the manifold or at tranny modulator, may also just be a bad modulator.
or  may be simple linkage adjustment
Are you handy with tools?
If so I can walk you through some things to do, if not , most mechanics familiar with old MB's should be able to help.  This is a common complaint

good luck
Ron