720 noisy chattering

[baumercase]

Hello, I am looking at buying a bobcat 720. However, it makes me nervous since when the controls are moved there are loud noises ,,the same noises as it makes when the controls for the aux hydraulics are moved. (the aux hyd are deadheaded, nothing hooked to them) Also, when operating the machine, once in a while the control levers started to shake in my hands,,??? I have very limited experience with skidsteers,,but lots of experience with forklifts,,and a hydrostat drive Lull high reach forklift..none of them have ever made this much noise under any condition....also,,my 580ck backhoe, which is very old and tired, makes very little hydralic noise,,, The dealer who has this machine says the drive motors were recently "gone thru"... the machine seems to function,,but feels ,,,uncomfortable,,,,jerky,, Any thoughts from you guys who know? cause I dont!! No experience,,from indiana,,lol Thanks!

 

[Tazza]

What kind on noise is it? a squeal or more of a grind?
Does it make the same sound when you bottom the lift or tilt rams out? like push the arms down and hold the pedal down and see if it does the same. It should just make a whistle as the oil runs over the relief valve.
The steering lever shaking may be because the suction line filter is blocked causing it to starve of oil, this will make the machine howl and it will have a serious lack of power. This filter doesn't affect the list and tilt functions though, ONLY the hydro drive.
The problem is this part of the machine if bad is very costly to repair.....
The "going through" of the hydro motors may just be a few O rings. These motors don't need touching unless there is a problem, they are very tough!

 

[baumercase]

What kind on noise is it? a squeal or more of a grind?
Does it make the same sound when you bottom the lift or tilt rams out? like push the arms down and hold the pedal down and see if it does the same. It should just make a whistle as the oil runs over the relief valve.
The steering lever shaking may be because the suction line filter is blocked causing it to starve of oil, this will make the machine howl and it will have a serious lack of power. This filter doesn't affect the list and tilt functions though, ONLY the hydro drive.
The problem is this part of the machine if bad is very costly to repair.....
The "going through" of the hydro motors may just be a few O rings. These motors don't need touching unless there is a problem, they are very tough!

the sound is different than when you bottom out the lift arms,but about the same as when you operate the controls for the aux hydraulics..I did forget to mention,,when you are just sitting still or coasting forward it is quiet,,the noise is loudest when you try to turn,, As far as the shaking controls,,I am not sure whether there was a loss of power or not,,I dont think so,,but not sure,,I just drove this thing today,,havent operated a skidsteer in yrs,,and not much then...the shaking startled me so much that I let go of the controls,,lol Are there seperate pumps for the forward motion and the lift hydraulics? And are the pumps variable displacement? or the motors? or niether? I do appreciate your reply, Thanks!

 

[baumercase]

the sound is different than when you bottom out the lift arms,but about the same as when you operate the controls for the aux hydraulics..I did forget to mention,,when you are just sitting still or coasting forward it is quiet,,the noise is loudest when you try to turn,, As far as the shaking controls,,I am not sure whether there was a loss of power or not,,I dont think so,,but not sure,,I just drove this thing today,,havent operated a skidsteer in yrs,,and not much then...the shaking startled me so much that I let go of the controls,,lol Are there seperate pumps for the forward motion and the lift hydraulics? And are the pumps variable displacement? or the motors? or niether? I do appreciate your reply, Thanks!

forgot to mention,,about the shaking controls,,,the control levers literally moved in my hands,,,I have NEVER had that happen on any other machine,,hmmm...

 

[Tazza]

forgot to mention,,about the shaking controls,,,the control levers literally moved in my hands,,,I have NEVER had that happen on any other machine,,hmmm...

OK, there are 2 pumps BUT they are in the same unit. One end does the left side, the other does the right side. It also has a charge/hydraulic pump attached to the front. The 2 pumps that control the hydrostatics are variable displacement piston pumps.
I think with my blocked filter my control levers shook around a bit too, but not do bad that they flew out my hands.
Any one else have any ideas?

 

[skidsteer.ca]

OK, there are 2 pumps BUT they are in the same unit. One end does the left side, the other does the right side. It also has a charge/hydraulic pump attached to the front. The 2 pumps that control the hydrostatics are variable displacement piston pumps.
I think with my blocked filter my control levers shook around a bit too, but not do bad that they flew out my hands.
Any one else have any ideas?

The steering levers should'nt shake though should they. Do these earlier machines have shocks on the steering levers to dampen movement?
If this guy is a dealer he should let you rent, or demo the unit for a day or so if it supposed to be in operating condition. It nomal for the drives to make more noise as you increase the load on them, but I'm not sure it should be shaking in you hands, if nothing else it would quickly play the opertor out.
Ken

 

[Tazza]

The steering levers should'nt shake though should they. Do these earlier machines have shocks on the steering levers to dampen movement?
If this guy is a dealer he should let you rent, or demo the unit for a day or so if it supposed to be in operating condition. It nomal for the drives to make more noise as you increase the load on them, but I'm not sure it should be shaking in you hands, if nothing else it would quickly play the opertor out.
Ken

There aren't any shock buffs as such on these. Just rubber bushings to take a little of the vibration out. I can't remember if cavetation shook the levers or not, i do remember they didn't want to move and were pulling away from me.