Skid Steer Severe Creep Lurch New Holland L445 Piston Pump Number 715313

[budyjim]

Has been an issue for the 20 years I have owned it. I am motivated to fix it as it is dangerous. the pump activation is unpredictable and unavoidable. It sometime engages at idle, some times when cold. Many times when trying to start it, the pump is engaged and I have to try and jiggle the control levers to get it to start. Both pumps (one on each side) misbehave, but one worse than the other.

I believe the the linkage to the activation shaft is wore and I would like to figure a way to repair it without removing the pumps.

should the pump "engage" when the shaft is in "nuetral"? Even though the shaft is worn, I am assuming it would not allow engagement until the shaft is activated.

1100 hours on machine.

I have included a photograph of a pump I think is similar. Also included diagrams of linkage.

I plan to work on this over the next few months, so not in a hurry for a response.

 

[oldnslo]

The skid steer should not move without a command from the operator. Once moving does it move smoothly in both directions or are speed & or direction changes erractic?

By design most hydrostatic transmissions default to neutral position. Either and external command like binding linkage or a stuck internal component in the pump will cause it make the machine move.

Do you have a parts breakdown of the pump?

 

[budyjim]

Once it is powered up and operating, it moves smooth and both directions. Most times when warmed up, it behaves as expected, but even then it sometimes engages without operator command.

some times when starting, a pump is "engaged" and when I jiggle or move one of the operating handles I can get it to "nuetral" to start it. Sometimes when I start it it is still engaged and I have to quickly take my hand from the key start to the operating handle to stabilize it. It also can "engage" by itself when the engine is idling and with no operator command. Just decides it is time to go. And as it is usually only one of the pumps that engages, it spins the entire skid steer. When it engages by itself, it fully engages, not a slow creep, thus the danger. both pumps engage at times, but I think one was worse than the other.

I remember when I purchased it at least 20 years ago, the prior owner telling me about it and advising that I be very careful.

I have included a parts diagram of one of the pumps, it is three pictures so the detail would be legible. I can also provide a hydraulic schematic if needed. Please ignore the three thumbnails at the bottom, I could not figure out how to delete them.

 

[oldnslo]

Budy,
From the parts diagrams it appears that the control linkage is directly connected to the pump swash plate (item 21) on the pump diagram. If this is true the first thing I would check is the linkage connection onto the pump control shaft. I suspect there is some form of key in the shaft. Make sure this is still in place and not worn. Then double check that your control arms always return to the same position for neutral.

If you can block the skid loader up so that none of the wheels touch the ground I would also try removing the control linkage from the pump and see if the wheels turn. They should not turn or should turn very slowly. If they turn fast there is a problem inside the pumps.

Good luck since skid steers are a pain in the butt to work on.

 

[flyerdan]

Normally that would be taken care of with a neutral adjust on the sticks, but since you're getting full engagement on one side that seems to indicate that something internal is amiss, especially since it will sometimes start in neutral and then suddenly engage.
You might want to also ask over at the skidsteer forum in the NH section.

 

[Ivan49]

I think there is an adjustment on those levers. But go over the other site and ask. I have an L 553 and mine was doing that but not as bad and I was told how to adjust it but that was many years ago and I don't remember how I fixed it.

 

[budyjim]

Curiosity killed the cat. I did not plan to work on this for a while, but could not help it.

I have included some photographs below. Please review the first photograph closely to see the damage to the shaft. The key groove in the pump control shaft is extremely wore. When disassembling, I did not even have to unloosen the bolt for the lever to disengage from the shaft.

The ID of the lever hole is .675 untightened and .658 tightened to extreme. The best I can tell the hole is quite round. the key shaft is a bit worn, but nothing like on the pump side.

The last photograph shows the lever when I have tightened the retainer bolt to the maximum. I think I bent it some, but plan to replace it with a SS bolt with two nuts. As there is a 1/4 welded chuck of metal added to the base lever, I also have the option to drill and tap three holes and add set screws.

Any other suggestions on how to fix this would be appreciated. I do have some experience working on customized shafts, pulleys and keys.


My hydraulic question: How much torque is on this shaft when the unit is at full operating RPM's, hopefully minimal?

 

[oldnslo]

Budy
How badly worn is the shaft and key way on the pump?

As far as torque on the shaft look at the control linkage to estimate operator input and mechanical advantage.

 

[budyjim]

I have re-posted the photograph of the shaft damage. Please review the photograph carefully, It shows the the wear of the shaft. It was dark in the garage, so I could not get a better photograph.

The damage is substantial, 24/4ths of the key way is worn away.

some parts of the linkage are heavy duty, like the linkage that directly connects to the shaft, but other parts are merely rubber bushings. Not much mechanical advantage, simply linkage from the shaft to the operator's hand, plus some shock absorption to, I assume, make for a smoother transition from forward to reverse.

 

[oldnslo]

Budy
You can try looking at the Eaton hydraulic or Sauer Danfoss website to see if they have the mechanical control option on their hydro pumps. Suspect your pump is in the 45 - 60 cc range. The data sheet should state torque requirements at pressure.

That pump shaft looks bad. Not sure how you fix that without dismantling the pump.