W123 300D transmission anecdote.. problem fixed
 

My '79 300D's trans acted wierd last week. It was not engaging until higher RPMs were throttled. Even then it was a bit weak.
So after checking the vacuum lines, linkage, fluid dip stick (pink, no graininess, no burnt color or smell), I had it towed to Peter Schmid Transmissions (MZF-Bayer, Inc.) in Burlingame, Ca. (south of San Francisco)

They are a very reputable and honest business specializing in Mercedes transmissions.

I got it back with a 'whew' because I was worrying that it might cost more than the car was worth to repair.
It turned out to be a "sticking valve in the valve body".

Very reasonable cost to repair and the car is back on the road.
Any other 'shop' could have taken me for a ride on this one !

So, if your trans has symptoms, it might be the valve !:)