J.D. 335-P boom float problem

[SkidTracks]

Wondering if anyone has seen boom float problems with John Deere skid-steer or compact track load?

When I first got 335-P, boom float worked without problems. After about 50-hours, boom float started having problems.

While stopped, the boom would float. But as soon as 335-P was driven forward or backward, boom would stop floating, go all way down, then release back to float position, and repeat cycle (boom all way down, release to float position). Even with right hand off joystick controlling lift and tilt, boom float problem would occur.

Found raising engine RPMs above idle would prevent boom float cycle from starting. As more use of boom float / increasing engine hours; it took higher and higher engine RPMs to prevent the boom float cycle.

Continuing to increase engine RPMs to prevent float cycle got to point of dangerous. With high engine RPMs (over 1,700) came hydraulic power to violently and rapidly shove boom down. Resulting in operator being thrown up/down in cab, only restrained by lap & shoulder safety belt.

Anyone experienced similar boom float problem, and knows what was replaced to fix the problem?

 

[SkidTracks]

John Deere had dealer replace the charge pump. According to dealer, it may have helped, but 335-P still has boom float problem.

The official J.D. 335-P repair manual (I bought via J.D.) does not have any drawings showing hydraulic flow, spools, pumps, reliefs, etc.

Does anyone know where I can find a schematic of hydraulic system?

 

[SkidTracks]

Took some effort, being CTL is construction (Yellow) and print materials have to come from different part of John Deere. But I was able to buy John Deere's Technical Manual (TM14841X019) which has hydraulic diagrams and information.

From what I can see, JD dealer didn't replace several parts which could cause Boom Float problem. After dealer replaced charge pump, they stopped working on 335-P. Even though Boom Float problem did not originally exist, and once problem appeared it got worse over time.

I am now looking to replace those parts and others parts out my own pocket.

Dealer is saying someone at John Deere told them Boom Float is "Working as Designed". Except there is no documentation to back up the claim. John Deere's construction support knows nothing about minimum engine RPM requirement. Neither does another John Deere dealer. The Owners manual and Technical manual do not mention any minimum engine RPM requirement. The operators control panel / 335-P's "brains", for operator safety, should have a restriction on enabling Boom Float when engine is below minimum RPMs.

Dealer is saying, minimum engine speed is 2,000 RPMs for Boom Float to work, without violent shaking. When 335-P was taken in, surprise-surprise, Boom Float problem was not happening above 1,850 RPMs. Originally, Boom Float worked from idle on up.

 

[SkidTracks]

Video taken back in mid-April, showing Boom Float problem when it first started happening.
In video engine is at 1,210 RPMs. Going above 1,250 RPMs, Boom Float problem did not occur.

Sorry for long lead in to Boom Float problem occuring, but I wanted to show Operator display and box blade attachment with front wheels.