1991 Chrysler 5th Avenue Air Cond vibration after repair

Hello, and thanks for your assistance in advance. I had to replace my condenser as it was leaking, and also replaced the compressor, high and low pressure switches, filter/drier, and expansion valve. After replacing, I vacuumed the system for 1 hour. Once vacummed, I added 8 oz of oil(from pressurized can) as per the rebuilder of my compressor. I then added alomost two cans of r12. The system seems to be cooling sufficiently, but at idol sometimes it starts to make one hell of a noise. It sounds like some kind of pressure noise, or like a train comming through. If you grab the lines you can feel the vibration when this occurs. Speeding up the engine and it appears to go away. Any suggestions?

Thanks Again