JD 3120 with 300CX loader lacks lifting power

[PahrumpBill]

Tractor is 2006 John Deere 3120 and has 1800 hours on it. 1000 by me. Hydro drive. No leaks or loss of fluid. High gear road speed has not changed...9.1 mph at 1500 rpm. I always run the tractor at 1500 RPMs. Several irritating problems with loader functions. Always at fresh start, when lifting bucket it pauses or jumps badly. As it warms up it is less noticeable. Over time I find I can not lift as much weight (pallet of bricks that was easily lifted before) or even when pushing into a pile of dirt the bucket lacks curl power. I have to stop forward motion and back out a little to complete the lift. During this action there is a slight lugging on the engine and drop of rpm but nothing like if I just deadhead into the pile without bucket action. I have noticed that the stick control of SCV is getting sloppy and sometimes I have to jerk a couple of times to get response. Not fully understanding the hydraulic pumps and system, I feel like I am getting bleed by or relief valve failure somewhere. Also the bucket and loader will drop off quickly 6 inches in an hour with bucket full of gravel. Also the 3-point will drop down a little over night. Another problem (not sure if normal) is that the bucket has a lot of free slop so when dropping to level on ground and trying to skid along surface, if the bucket starts to dig on its own, it will continue to dig deeper and suddenly you have very little control of angle unless radical changes to control is made. I do a lot of back dragging with bucket and float works well after you adjust for angle slop. I have checked and reconnected QCs - no help. Changed Hydraulic filters and fluids - no help. I am 180 miles from dealer where purchased and no means of transport. I am an older gentleman with good mechanical skills and equipment. I have the repair manual for 3120 but at JD prices I can't just start slapping parts to it without some educated starting point.
Any help will be appreciated.

 

[swines]

When is the last time ALL of the hydraulic filters were changed and the hydraulic fluid? If the filters are dirty and the hydraulic oil is starting to break down, they will both affect hydraulic performance.

 

[PahrumpBill]

Not sure, but over 500 hours ago. I did NOT use JD fluid. Napa with same specifications. Am getting ready to change again but wanted to wait incase I have to drain to get into system. However, you reminded me of a strange situation. I inherited the tractor from my father who has deceased. When I changed the filters and fluid I realized the suction filter had never been changed - canister was still painted closed and had a devil of time taking can off. I was assuming my father had never changed fluid but now not sure. He could have changed fluid but not filter. That was around 800 hours. Now that I think about it, the hydraulic whine is much louder than I remembered when I got the tractor. I know there is a lot of controversy about using JD fluid or not. Just maybe it is worth the $200 investment to get J20C fluid, filters and see what happens.

 

[Dave M7040]

Back dragging may be the clue. It is a method of operation with a long history of bending and breaking bucket cylinders.

The linkage, which allows more bucket curl back, also works to amplify the forces bucket can put back into bucket cylinders causing damage such as bending of push rods and separation of piston from push rod.

When the loader valves are in the middle position, the loader relief valve is no longer in the circuit and unable to protect the loader.

To understand the above, picture picking up a bucket of gravel with the loader just managing to get the bucket off the ground.
Now go and shovel more gravel into the bucket. You can keep adding weight until a hose or something else breaks in the hydraulics.

If one of the two bucket cylinders are damaged internally, the result can be the erratic operation you are experiencing.

The cylinder test procedure I will attach enables a comprehensive cylinder test at minimal cost.. just need a few hydraulic caps and plugs to seal hoses etc.

Dave M7040

 

[PahrumpBill]

Thanks Dave and swines. I printed the cylinder test and will perform in near future. I am also going to go ahead and do a hydraulic filter and fluid change as well as engine oil and filter change. I know the tractor has been used hard and abused. Time to make amends before it is too late.