Same thing happened to mine a few months ago at 230K. Was heading to my mechanic to fix a slipping tranny when I ended up stranded in an intersection. I could rev the engine in D -- and no go.

Turned out I had a broken brake band in my tranny. The fix: a $1,500 rebuild.

Good luck.

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'91 300D 2.5 Turbo 330K
'00 VW TDI Golf, 190K
'67 BMW R50/2
'73 Norton Commando Interstate