360 vibration issue

[72 scamper]

Hello all. i need some tips about my 72 scamp vibration. the car vibrates real bad between 1500 qnd 3000 rpm in park. 55 to 65 mph is pretty rough on the vehicle. the motor is pretty stock internally. 360 eng, in front of a torqueflight 904 the 360 swap from the 318 was done maybe 10 - 12 years agoi remember using the 318 balancer on the motor instead of the proper externally balanced dampener. replaced that just this year and the vibration wasnt so bad but it didnt solve the issue. i have brand new stock motor mounts and a high performance trans mount. it seems that the vibration became very aggressive once the performance trans mount was installed. the flexplate is a high performance B&M plate which is like a drumkit symbol with a small round pie cutout. didnt use weights on the convertor with application because of that. hope this helps. thanks for any tips

 

[DartVadar]

The balancer was the problem initially, a 360 is externally balanced where a 318 is internally balanced. That is the correct flexplate though.

My cousin had a mustang that had a bad vibration, spent hours trying to fix it, we though it was the cross-member for the trans because it was upside down, that helped a bit. We ended up pulling the motor out, 2 main bearings were finished. The crank was bent or something, no idea how that happened. But if it was vibrating for all those years it may have damaged the bearings and crank. Not 100% sure though.

 

[gliderider06]

Do you have the correct flexplate? Could it or the balancer be one for a cast crank 340 or 440? Does the block also say 360 on it?

 

[Rapid Robert]

See if the flexplate is a B&M 10239.

 

[72 scamper]

thanks for the feedback guys. helps me so much. can i get to the crankshaft and bearings and hopefully have a positive result after replacement or am i going to have further problems? i went thru all the steps to get this flexplate right and then later to get the balancer proper. i work at a dodge dealer and can get this done but . i have one more question. when i upgraded the trans mount , all hell broke loose with this vibration and i was unable to ride on the highway comfortably. the old mount was rough but it was shorter and not even close to as stiff as the new one. would u advise me to use the stock mount to see if it will do highway speeds , or is this going to kill my motor more ?