1977 280SE Transmission Problem

Not sure if my tranny went on mr last night but the car was running fine at 300 rpm then suddenly it chokes, shoots the rpm to 5000 then I lost power. Right now, it will just hmmm and purr when you start the engine but it doesn't want to go anywhere, that includes reverse too.
So do I have a dead tranny or is it a matter of looking for a broken linkage or leaking vacuum line. Please help!!

correction on my post. That's suppose to be 3000 rpm and not 300.