Just bought a sweet 69 with a THM 350 transmission.. Got a great deal because it possibly has a bad trannie. The previous owner told me that he was moving the car around the driveway with no brakes, couldn't stop so he threw it in reverse while moving forward about 5 miles an hour and heard a loud clunk. Then while moving backward, he threw it in drive and heard another loud clunk, before turning the car off. After this even the car has the following problem.
The drivetrain shakes pretty bad in park and while idling in drive. The shake goes away while driving, the engine runs great and trannie seems to run great in 2nd and 3rd gear. But the shake comes back again right when the transmission downshift to 1st gear when stopping for a traffic light. The shake continues while idling at the light, and the cycle repeats again.
Already check the engine and trannie mounts. All vacuum lines are OK,
Any ideas. I guessing torque converter or something to do with the input shaft on the trannie.