Long story short, ole blue (my old 77 E150) had a bad shake at 60 or above. I had just put tires on it at another shop so I figured they needed rebalanced. The other shop rebalanced them but does not test drive the vehicles afterwards. I got it back with the same shake. I took it to Southern Tire and his guy test drove it before doing anything. Pulled up 5 mins later and said my tires are fine and said I had a driveline vibration. I was skeptical only because I had inspected everything front to rear on ole blue recently including u-joints etc. Sure enough, I bring her home, pop the engine cowling off and put it in drive while holding the brake. The drivers side of the engine raises up and drops. Mounts are shot. Been in there since 1992. Had no other indications of worn mounts. No noises, thuds. Nothing. I tried paying Southern Tire for the diagnosis but he refused and asked me to report back my findings. He’s got my business from here on.