Ok. Googled the year, Volvo BM straight model. On the main control valve in the front section , you should see 3 adjustable cartridge valves adjacent to boom up, tilt in and tilt out. I dont think there is one for boom down. These are your shock valves. They all have the same part number.
Block up your boom and bucket. This means use adequate support under boom arms positioned so they cannot be moved. NO, digging your cutting edge into the ground on a high angle is NOT ACCEPTABLE! Safety first. You can only make this mistake once.
Once boom is supported, you can remove the cover off ftont frame. Now you will see the shock valves. Go back in the cab, start it, shut the key off and relax all the hydraulic energy. Preferably hold in boom float.bucket should be hanging free as well. The shock valves, Theyre rather large 1 1/4 -1 1/2 by 3 - 3 1/2" long. Mark each one. For testing purposes, you can swap boom up with say curl out. Raise your boom and see if she drifts. If the drift stops, put them back where they were and order a new one. They can be purchased over the counter, service dept will adjust setting for a fee. Specs are all a little different.
Aside from shock valves and cylinders, things get a little hairy.