Its an old 'trick' from way back when ....... Usually done to small diameter shafts and more recently the 2piece shafts found in more 'modern cars'. Large diameter tubes, Bedford vans / holden 1tonner shafts for example, dont suffer from resonance issues that the human ear can detect (probably drive elephants nuts tho, so if you see an elephant driving a 1tonner you can ask him..... ) :rofl: Old mate had issues with an Escort shaft, I drilled a hole in each of the cast ends and filled the mutha with expander foam........ problem solved & with no re-balancing required. Kingy
Dont know if this helps - but Resonance is really bad vibration - it will even crack welds. The military uses rubber to counter resonance - rubber is excellent at dampening resonance and vibration. It should be packed with rubber or use rubber mount points. Some use flat rubber rings around the diameter (if it requires tuning for some reason- then grooves are normally provided in sequence with flat rubber rings)
