All functions work normally except raising the boom will jump as your raising especially when low to the ground pressures checked all 4 of the cyl hold valves replaced Any ideas????
Could be binding on the heel pin or the cylinder pivot pins, most of those telehandlers don't see a grease gun much. I rarely find the holding valves to be a problem. Mostly its piston seals. The cylinder barrels/ piston seals could be worn, you could actually have a swollen spot in the barrel, where you commonly drive around with a load on. i.e. a bunk of plywood bouncing around on the forks while driving on a rough jobsite, can cause damage.
Definitely try and get some grease into the boom pin and the lift cylinder pins first. It'll be the cheapest thing to try first.
Thank you for the reply and ideas! Cylinder pivot pins and bearings have been changed. Heel pins have been greased. may have to pull cylinders and check the barrels and seals. will keep you posted
Did it jump before you switched the check valves? Or only after they were changed? Its possible you have air in the system, if its only after you changed the check valves.
No it was jumping before as to why the check valves was replaced per JLG advise.
Finally rebuilt both main boom lift cylinders to fix the issue!!!
That's great. Those lift cylinders take a beating driving around job sites.