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JD 790 d lc hydraulic power issues

Southshore1

New Member
Joined
Jul 15, 2021
Messages
1
Location
Ohio
Bought it a few months back to have a machine at my shop and haven't used it much. I own a marine construction company and tried to use it to unload a boat I bought off trailer, the boat probably weighed between 4-4.5 tons. I couldn't get it to pick it up but I tried to track forward while raising the boom and with me moving the tracks and lifting it lifted up no problem but without moving the tracks it can't. I changed filters and fluids when I bought it, and repacked the boom,stick, and bucket pistons (they all leaked) any ideas?
 

mg2361

Senior Member
Joined
Jul 5, 2016
Messages
5,057
Location
Pennsylvania
Occupation
Equipment Mechanic
Welcome to HEF Southshore1;)!

You need to check system relief pressure. Check at fast idle with boom up stalled. Curious to see what you have. When propelling while booming up removes the system relief valve from the equation and the propel relief takes over which is a higher pressure.

Another question, how were you lifting. Over the front, over the side, height of the load being lifted and how far from the centerline of the machine was the lift?
 
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