I have 66 dodge dart gt and it has a shake got 4on 5 original wheels and good tires and balanced at three different places got driveline balanced could it be my motor mounts; cause mechanic that rebuilt engine said mounts were bad . Do you think this is my mystery shake?

Could be your motor mounts, another place to check is your tranny crossmember mount.

Does the shake occur at any particular speed or rpm range, or is it constant, or does it get worse with speed or rpm?

-Aaron

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The "Silver Bullet"
87 Ram D150

Does the car have the original engine / trans in it? (how many freeze plugs in the engine block?)

Does the slip yoke go into the trans tailshaft almost all the way or is it 1/2 "hanging-out"?

Does the car shake when reved-up in neutral?
DD

Iwill check on freezer plugs? But Why... I will check on nuetral shake but I dont think so its usually only at about 40 mph and the it sort of goes away but still subtly there...The yoke seem to go in all the way I will see if it sticks out ainch and a half, I will check the tranny cross mounts but the guy that rebuilt my tranny would have seen that huh Thank- you and glad to hear more.... Pat

A 66 SL6 should be orange color and have 3 freeze plugs. (up to 1967)
68 and later engines have 5 freeze plugs and are blue color, the later engine also has a larger hole in the back of the crankshaft, where the tranny torque converter "plugs-in".

If someone swapped a later engine into your 66 and did not use the special adaptor ring needed to support the small converter nose, the driveline will vibrate as you discribe.
That is why I asked about the number of freezeplugs. BTW, what color is the engine block?
DD

Doc thank-you for staying with me on this, when the engine got rebuilt they also painted it and it orange it is the original. I will also go and make sure its got 3 freezer plugs.. If thats the case it doesn't shake in nuetraland only sometimes when I pull out and really bad if its been sitting for a monthy...