Car emits a solid thunk under strong acceleration from a standing stop.
Engine/tranny mount?
I first thought it was steering as I had a worn tie rod but it still thunks after I replaced the rod.
Any particular procedure to follow to check the mounts?
If one is bad should I replace 'em all or only the bad one?
As far as I know, they are all original.

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1999 E320 (gave to daughter) 250K
1994 F150 (may be the end of its road) 240K
1989 560 SL (Reassembly after paint job) 160K
1986 560 SL (deceased., gave it's life protecting my wife)
1988 300 TE (departed)
1994 945T (still running strong with an upgraded cam) 349K
1986 242Ti (deceased)
1968 GT500KR (under restoration)