The transmission mount is a rubber/steel unit which bolts to both the cross member and the tailshaft housing of the transmission, it secures the tranny to the frame. The flex disk should be easy to spot, by your description of things, it should be the black round rubber piece which is rubbing on the tunnel. Found as the union between the transmission yoke and the front yoke of the driveshaft.
Hope this helps.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
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