425 again…movement problems…

[Modrob]

Depending on the control system you have, they all can go out of alignment.

As @m5040 mentioned a certain amount of whining at low oil temperatures is to be expected to happen due to higher oil viscosity, but try to minimize it by letting the oil warm up. I believe that @MossRoad starts his and lets it run for a while (15 min?) while he does some hand shoveling. If your pump is not in trouble, the whining sound is the oil cavitation as it is being pump and the cavitation is very hard on, and damaging to, surfaces.

All the best,

Peter

Thanks again. I started reading about cavitation. One site mentioned this, concerning viscosity and cheap to expensive fluids:
“Therefore, most hydraulic systems should not be started up with the oil any colder than 40°F and should not be put under load until the oil is at least 70°F.”
Wow! The article was dealing with factory-type equipment and systems but I believe some of it extends to our equipment…

 

[ponytug]

Thanks again. I started reading about cavitation. One site mentioned this, concerning viscosity and cheap to expensive fluids:
“Therefore, most hydraulic systems should not be started up with the oil any colder than 40°F and should not be put under load until the oil is at least 70°F.”
Wow! The article was dealing with factory-type equipment and systems but I believe some of it extends to our equipment…

It does, and it may/is probably one reason why Power-Trac recommends 10W40/15W40 instead of the usual 30W hydraulic fluids used inconstant temperature settings like factories. Some other tractors with hydraulics actually have heaters, electrical or diesel powered, to warm the oil before the tractor can be operated.

Eberspacher is a well known brand of diesel fuel heaters used to heat trucks and heavy equipment. They are high quality, but it does take time to warm hundreds of pounds of metal and oil... Here a video of a creative guy, living north of the arctic circle on the Sweden/Finland border installing one in his excavator;

All the best,

Peter

 

[Modrob]

It does, and it may/is probably one reason why Power-Trac recommends 10W40/15W40 instead of the usual 30W hydraulic fluids used inconstant temperature settings like factories. Some other tractors with hydraulics actually have heaters, electrical or diesel powered, to warm the oil before the tractor can be operated.

Eberspacher is a well known brand of diesel fuel heaters used to heat trucks and heavy equipment. They are high quality, but it does take time to warm hundreds of pounds of metal and oil... Here a video of a creative guy, living north of the arctic circle on the Sweden/Finland border installing one in his excavator;

All the best,

Peter

I was adding yours and more info to my ongoing file and reread MossRoad’s details and pic about hydro back. It seems I didn’t remember, but it appears the only adjustment would be the cylinder and mount that can be slid in its bracket. Since I had lifted the unit on all fours and found no movement when started, and the pedals operated as they should, then there really isn’t any more adjustment. So I believe I can rule any simple adjustments out. I’ll be out of town for several days but when I return I’ll start digging deeper into the cavitation route….

 

[ponytug]

I was adding yours and more info to my ongoing file and reread MossRoad’s details and pic about hydro back. It seems I didn’t remember, but it appears the only adjustment would be the cylinder and mount that can be slid in its bracket. Since I had lifted the unit on all fours and found no movement when started, and the pedals operated as they should, then there really isn’t any more adjustment. So I believe I can rule any simple adjustments out. I’ll be out of town for several days but when I return I’ll start digging deeper into the cavitation route….

Not a lot to be done about cavitation; slow the engine speed down, especially when cold, don't work it had while cold, and possibly change the hydraulic oil to fresh 10W40. How does the hydraulic oil look? Do you know when it was last changed, and what oil was used?

If the pump is worn it may be more prone to cavitation and there isn't much to be done about that.

All the best,

Peter

 

[Modrob]

Not a lot to be done about cavitation; slow the engine speed down, especially when cold, don't work it had while cold, and possibly change the hydraulic oil to fresh 10W40. How does the hydraulic oil look? Do you know when it was last changed, and what oil was used?

If the pump is worn it may be more prone to cavitation and there isn't much to be done about that.

All the best,

Peter

I did a change probably little more than a year ago, and filter. But it’s only been run maybe 10 hours since then. Still looks good. I can’t recall the exact oil but I followed recommendations from folks here.

 

[ponytug]

I did a change probably little more than a year ago, and filter. But it’s only been run maybe 10 hours since then. Still looks good. I can’t recall the exact oil but I followed recommendations from folks here.

Great! Was there any sludge in the bottom when you drained the old oil? Particularly anything magnetic?

I may have mentioned this, but one other item that can cause some cavitation is an air leak at the suction filter. The easiest way to check that is to run the tractor for a bit and then look in the hydraulic tank with the engine running (with the brakes on!), and check for bubbles or foaming.

All the best,

Peter

 

[oldnslo]

Mobile equipment if designed properly can and will operate well below 40 degrees F. This becomes a factor of pump inlet conditions like hose diameters, lengths, etc. along with oil viscosity.

If you are having issues with cold weather starts maybe consult with manufacturer to see if there is an option for lower viscosity oil like 5W-40 for colder climate vs 15W-50 for warmer climate. What is your ambient temperature in summer since you also need to consider that when selecting hydraulic oil for your equipment.

 

[m5040]

IMPORTANT, people with the hydroback cable to control fwd/rev on the Powertrac must make sure the connections throughout the control "chain" are in good condition. Especially the arm pined to the hydrostatic pump. If the pin was partially sheared, it would limit the travel from the foot control, and if you keep using it, the pin would shear, and you would have no way to control the drive system other then kill the engine. To check, closely watch the shaft on the pump as the treadle pedal is cycled. If you see any movement in the arm without corresponding rotation of the shaft, check/replace the pin that secures the arm to the shaft.

Also cavitation of a hyd pump can come from leaks in the suction side (from hyd pump intake to reservoir). A "leak" might not actually lose oil, (air is thinner than oil), but could allow air to enter the oil stream when the pump is drawing in cold-thick oil. The air causes the noise and damages the pump internals.

 

[ponytug]

Mobile equipment if designed properly can and will operate well below 40 degrees F. This becomes a factor of pump inlet conditions like hose diameters, lengths, etc. along with oil viscosity.

If you are having issues with cold weather starts maybe consult with manufacturer to see if there is an option for lower viscosity oil like 5W-40 for colder climate vs 15W-50 for warmer climate. What is your ambient temperature in summer since you also need to consider that when selecting hydraulic oil for your equipment.

While this may be generic advice, it does not apply to these machines.

It is worth examining an oil viscosity chart for the data.

There is almost no difference in cold weather viscosity between 10W40 and 5W40, and the exact same viscosity at higher temperatures. (The two columns on the right are cold, then high temperatures viscosity. A 10W40 oil might be 120SUS cold, and 70SUS hot, while a 5W oil is closer to 95SUS cold.

@Modrob don't use less than 10W40, per the factory. (And great advice from @m5040)

All the best,

Peter

 

[oldnslo]

Not trying to start a war but what makes a power trac hydrostatic drive any different than a skid steer or any other hydrostatic driven vehicle?

 

[ponytug]

Not trying to start a war but what makes a power trac hydrostatic drive any different than a skid steer or any other hydrostatic driven vehicle?

No worries.

I think that the design, and to lesser extent operational differences make Power-Tracs quite different from skidsteers and most other hydrostatic drive equipment. Power-Trac machines are wonderfully simple, solid machines that lend themselves easily to shade tree repairs. However, that means that they don't have the bells and whistles that you would find on a John Deere or Bobcat. In particular, the 425 that @Modrob is dealing with has a gasoline powered engine (similar to your x540) that usually runs at a fairly high throttle, ideally wide open due to air cooling issues intrinsic to the particular engine. That means that the pumps are running at full speed, when they are most prone to cavitate.

Bobcat, CAT, Kubota and others are generally diesels that in normal operation are running at low throttle most of the day. Many have mechanisms on their machines, or at least the ones that I am familiar with, that help get the hydraulic oil to temperature quickly, and many suggest in their owners manuals that the machine not be operated or moved in cold temperatures until the machine and its oil are up to temperature. That is also why many of those machines are designed for, and use, straight 30W hydraulic oil, as the manufacturer expects the machine only to be used when the oil is at temperature.

I'm not saying design version X is better, or worse, than Y, just that there are some significant differences between Power-Tracs and more common machines, and that experiences with other machines may or may not carry over to Power-Tracs. E.g. The only interlock on a Power-Trac are the starter key, and a PTO lockout during starting.

Over the years, I have operated a wide range of tractors, and I will say that for the purposes of our current property that has significant slopes, "There's nothing like a Power-Trac". Horses for courses. These are not your typical tractors, and that's why generic advice can be off base, but there are reasons why Power-Trac owners tend to be fans.

On the other hand, I would never attempt to pull a plow with a Power-Trac; low speed, high torque, ground traction isn't their design, nor is it going to haul a grain cart or a baler well.

Being a Swiss Army knife type machine that is excellent on slopes is what Power-Tracs excel at. A neighbor down the road was killed when he tried to operate a standard tractor on slopes.

All the best,

Peter

 

[m5040]

Not trying to start a war but what makes a power trac hydrostatic drive any different than a skid steer or any other hydrostatic driven vehicle?

Spin on suction filter for one, which is not a typical arrangement and requires adherence to the oil specs and service interval of 50 hours for a filter change.

 

[oldnslo]

Spin on suction filter for one, which is not a typical arrangement and requires adherence to the oil specs and service interval of 50 hours for

The suction filter is not that unusual since both the BX1850 I had and 2400H I have now had them.

The 50 hour filter change does seem unusual though

 

[m5040]

The suction filter is not that unusual since both the BX1850 I had and 2400H I have now had them.

The 50 hour filter change does seem unusual though

I am just trying to learn here. Why do you think the BX1850 trans filter is on the suction side? The parts diagram shows one filter integral with the transaxle and without a internal flow diagram, it most likely is filtering returning oil (it is easy to push unlimitedly through filter media, but vacuum to pull oil is limited to atmospheric pressure).

The 50hr filter change is due to PT using it on the suction side. I don't like this setup, but it works. I have seen neglected Power Tracs for sale that, at least appear, to not have had the hyd filter changed in years and yet the drive still works.

 

[oldnslo]

The reason the filter is on suction side on utility is that the return oil is typically from 3 point hitch valve which dumps straight into the transaxle. On my 2400H their is a suction filter for both implement and charge pump and also a spin-on filter for the pressure inlet of the charge going into the HST.

The suction filter or screen is there to remove contaminants generated by the turning gears in transaxle, particles from PTO clutch, wet brakes, etc.

I agree that suction filter is not ideal but sized properly they do work.

If 50 hour change is required I would suspect a design problem with either a component generating a lot of debris or a very undersized filter since as filters remove contaminants the pressure drop across them increases.

 

[ponytug]

The reason the filter is on suction side on utility is that the return oil is typically from 3 point hitch valve which dumps straight into the transaxle. On my 2400H their is a suction filter for both implement and charge pump and also a spin-on filter for the pressure inlet of the charge going into the HST.

The suction filter or screen is there to remove contaminants generated by the turning gears in transaxle, particles from PTO clutch, wet brakes, etc.

I agree that suction filter is not ideal but sized properly they do work.

If 50 hour change is required I would suspect a design problem with either a component generating a lot of debris or a very undersized filter since as filters remove contaminants the pressure drop across them increases.

The filter is a little on the coarse side (30 microns), but many machines have even coarser filters. My recollection is that the logic on the filter choice and size is that unlike other machines with 30W oil and warmer oil, the filter on Power-Tracs has to deal with cold oil without collapsing. The filter feeds the charge pump for the variable volume pump, so the flow starts on engine startup, again, not always the case on other hydrostatic machines. A filter collapse would probably be terminal to the main pump, hence the low hour filter change requirement.

Could things have been done differently? Without question. One could treat the hydraulic tank as "clean" and filter 100% of the return fluids, and many of the larger machines do exactly that. PT chose not to do that in the pursuit of lower engine loads. It was a design choice, and it seems to work.

As I wrote, PTs are a little different...

All the best,

Peter

 

[oldnslo]

Peter,
I don’t know of a hydrostatic system where charge pump does not turn when engine starts. All hydrostatic systems require a charge pressure to operate without self destructing. On some designs the charge pressure is used to stroke the pump so without charge pressure the machine will not move. I believe but not positive that PT uses a direct mechanical control to the hydrostatic pump so it will move without charge pressure IF the closed loop portion of system is full of oil. With charge flow system leakage empties this circuit and cavitation begins.

 

[m5040]

I don’t know of a hydrostatic system where charge pump does not turn when engine starts.

I have a Kubota powered Hustler Excell that starts without the charge pump or any other spinning.
The later model Power tracs have pilot control for the drive system.

 

[ponytug]

Peter,
I don’t know of a hydrostatic system where charge pump does not turn when engine starts. All hydrostatic systems require a charge pressure to operate without self destructing. On some designs the charge pressure is used to stroke the pump so without charge pressure the machine will not move. I believe but not positive that PT uses a direct mechanical control to the hydrostatic pump so it will move without charge pressure IF the closed loop portion of system is full of oil. With charge flow system leakage empties this circuit and cavitation begins.

Some models have mechanical control of the stroke. Mine doesn't.

Not all brands of hydrostatic drive machines support cold movement, per their manual, although it might be possible for some, I don't know.

To me the distinction is whether the system is designed with a warm, clean oil reservoir in mind, or not. If not, then the filter has to be able to deal with high viscosity oil without failure. I did the math a while back, and it turns out to be a rather big ask to limit the pressure drop to be within the filter's rating at low temperatures. I was surprised. One fix could be that one could use a high pressure rated filter suction filter ($$$), but while that helps not to have a catastrophic filter failure, it could (would probably) introduce degassing due to the large pressure difference across the filter, and air bubbles are really hard on pumps. So, I don't necessarily think that is a win, but might work if one was just warming a machine up.

I think it all comes back to design. Power-Trac seems to have designed for cold oil intake of not necessarily clean oil, putting a large filter (low pressure differential with cold oil), but needing to be changed frequently to maintain the low pressure differential.

All the best,

Peter

 

[Modrob]

Not a lot to be done about cavitation; slow the engine speed down, especially when cold, don't work it had while cold, and possibly change the hydraulic oil to fresh 10W40. How does the hydraulic oil look? Do you know when it was last changed, and what oil was used?

If the pump is worn it may be more prone to cavitation and there isn't much to be done about that.

All the best,

Peter

Hey Pete…back in town again and had a chance to look back at the oil I put in—it was 5w30, and that was what I was advised to put in at that time. (And new filter)