455G Boom Cylinders Hammering Noise

[jwalk2c]

Hello all,
Loader was working fine and then I noticed a knocking or hammering noise when lifting boom. With engine running it was not obvious to me what this sound was or where it was coming from. After about 30 min or so I finally stopped working for the day and returned loader to put up on blocks to do some other work. I wanted to investigate this sound further.
The hammering sound appears to be coming from the boom cylinders, beginning through mid point in the lift cycle continuing through the top . And same on the way down. With engine off it is very loud and pronounced on the way down.
The sound only stops at approx. last 25% of downward travel.
Loader has 1185 hours and I changed hyd. filter about 15 hours ago.
I was preparing to change hyd. fluid and filter because I do not know what previous owner (State Of Virginia) did at 1000 hours.
Any suggestions is appreciated.
I am already dreading this expense. From what I read from googling, I will most likely have to call in some outside service.
btw; I posted this on Heavy Equipment Forums as well. There are a bunch of good people over there as well.
Thank you
John Walker

[Jim B]

How are the linkage pins and bushings? A bad one could be binding and popping as it moves. Grease well, cycle a few times and grease again, worth the cost of the grease to try.

[jwalk2c]

Thank you for the reply.
Pins and bushings are in very good condition.
Ironically I just greased it the day this started.
I actually over-grease this machine according to the instructions on the door, which calls for 2 pumps ever 100 hours and 2 pumps ever 10 hours on the bucket pins.I grease every fitting approx. every 5 hours or so.
This machine is just for personal use and I don't get to use it very much. I try to crank it and move it every month .
I did verify that the sound only occurs when boom is raised up or down.
Bucket tilt and 4n1 are normal.
Here is a you tube video I made today with engine off that demonstrates sound on down cycle of boom.

https://youtu.be/5BG5ovY45C8

Please copy and paste link in your browser.
Thank you

[jwalk2c]

Thanks again for the reply.
I will grease again, this time I will grease with move boom in multiple positions. Maybe that will help distribute grease.
John