Combines only 1 response to my 6620 hyd IJ

It sounds like you have a hyd tubing chattering against some iron,trace all your piping and tubing and see if the clamps are tight and nothing is rubbing,also check the hyd hoses,they could be rubbing and chattering.One other thing you could try(and this happened on my 7720)is that the rubber cab mounts, there are 2 on each side underneath the cab torwards the front,over the yrs the rubbers settle and throws the cab out of alighnment and you get all kinds of wierd noises. I spent 2 yrs on mine trying to pinpoint a grinding sound and finnaly out of desperation i lossened the 4 cab mount bolts and jacked the cab up,then put 1_2 in spacers ont top of the rubber mounts,cured all my noise problems,hope this helps.

I think I know what you are talking about. We had this problem on a 9600 it would make some hyd lines jump and quiver it always seemed to happen when we would turned the steering wheel real tight to the left never did figure out what caused it so I guess I havn't helped you a bit.Sorry

Sure sounds like it could be a relief valve some where that has some crap migrating through the system. Sucking air on the intake side of the pump could also cause a chatter. If you are sure it is in the hydraulics you could plumb in an accumulator to take up the shocks just to make it barable to operate. Cab vibration could also be the culprit as some others have suggested.