It could very well be the shock absorbers, you can probably diagnose this yourself by pushing the drum up and down quickly to see if there is any resitance from the shocks and replace if not. However, it could also be a foreign object such as a coin stuck inside the drum, so check for that by tipping the machine to see if you can hear anything rolling about inside. Finally, you might also want to check the bolts securing the concrete counter-balance weight are fully tightened, as this issue would also cause the noise you are hearing.
Rupert, March 2020
