2910 Steering problem

[hayden]

OK, now I see what you mean.

Is the -2 image really the PS return line? It looks like it may be a different return line for a different purpose.

The 2710 WSM that I have only shows the split return line, even in conjunction with the strainer. I've been under the impression that the return line has always been split and has not changed.

Peter

 

[Anonymous Poster]

Hey guys,
I was away from the computer for a few days, catching up tonight. A few thoughts on the contamination theory. With just the srainer set up on (lets call it the first generation B2710) there's a good probability when removing the strainer that some of the "crud" will drop into the suction line, if it's not cleaned out it will go directly into the pump, wich may be the reason for the new spin-on filter to alleviate the possibility of this happening, may be the only reason other than ease of maintenance or a higher micron rating. But I feel the different filter point of solving the problem really is'nt a factor in determining
the cause of this failure due to the fact that the problem is still occuring regardless of the filter set-up. Fluid type also doesn't seem to figure into the equation. So far the only common denominator appears to be fluid temp at time of failure. Possibly pointing toward mechanical tolerances in the pump or more likely in the steering assy. itself. Thermal expansion creating a negative pressure in the wrong place inside the steering valve assy. causing the temporary loss of pressure. Basically the way the steering valve is actuated is through the torsional deflection of the steering shaft itself (twisting moment). Probably the best piece of info required for this problem would be fluid temp at time of failure. Keep in mind the temp would have to be measured at the same location in the system on every machine. I would suggest using temp tape at the line coming directly out of the pump.

 

[Anonymous Poster]

Peter: Checked with my dealer yesterday. He confirmed that the return lines do run as I described. The split line is only on the newer design. Kub-mech has posted a message since your last reply. His comments about heat are pretty much what I feel is the problem. By adding a second return line. Some Oil from power steering is returned to the trans instead of heating up the suction line oil.

 

[hayden]

I agree that failures on 2910's (with the dual filter arrangement) runs against the contamination theory.

But the other important piece of data we have is a somewhat scored pump followed by pump replacement that had a marked improvement in steering performance and at least the appearance of eliminating the problem to the extent it was reproducable on that machine.

This is the most meaningful clue so far in my opinion since it's the only direct cause and effect thing that we have.

The other piece is to look at what's changed. Not so much what's changed in the 2710 design during its life, but what's changed between the 1700/2100/2400 series and the 2710/2910. The big change is the replacement of a single pump and diverter value with dual pumps. This problem has only been reported on 2710 and 2910 machines. Do you know if the steering unit changed with the introduction of these machines compared to the B2400, for example. That might yield a clue.

Another question. I'm still not clear on whether the B2410 has the dual pumps or if it's only the 2710/2910. If the B2410 does not have dual pumps, hat would be a significant clue since the problem has not been reported on those machines as far as I know.

At this point I think the problem is related in some way to the dedicated pump and/or different oil filtering and plumbing, since that's what's changes with the intro of these machines. Whether it's overheating oil, cavitation (although I think we're mostly ruled that one out), or component damage is not clear. But the only case on hand of the problem being reproducable, changing something, and the problem going away is when you replaced the pump. That's the best hint we have so far.

 

[Anonymous Poster]

The B2410 has a dual pump just like the rest of them, in fact my first thoughts on the problem I experienced, due to the fact that all three model pumps look identical but have different part numbers and flow specs, was that maybee some B2410 pumps found thier way onto 27+29's especially due to the fact that the manual depicts two different flow ratings
for the PS side between 27/29's and the 24. But I was assured by my rep that, that must be a misprint in the manual. Just to be sure I checked the parts manual, and the gear pump section of all three tractors is the same on the steering side. The steering system on the B2400 is different. I believe (let me check) that the unit on the B21
is the same.

 

[Lloyd]

I have a B2410 and it has the same problem of hard steering after an hour of mowing at high speed. After a straight run if I try to spin the steering wheel with a spinner to make a tight turn the spinner jumps out of my hand.(also known as a necking knob, in my time.)

 

[Anonymous Poster]

B21 same basic design, different part number. B21 hyd cooler cools entire sytem including steering and has much larger resevoir (oil stays cooler) B24,27,29 cooler only
cools HST circuit. Much smaller reservoir.
B21 uses single hyd pump for all functions, rated at 8.2 gpm with priority valve. B24,27,29 has dedicated steering pump rated at 3.1 gpm.

 

[Anonymous Poster]

Uh-Oh, do I see our first 2410 with the problem?

 

[hayden]

Today I finally got the correct parts and WSM for the 2710/2910.

Here's the explaination for the return line, as I see it.

In early model 2710's, the return from the PS dumped into the pump intake only. The reduction gears in the clutch housing are tied to the rear trans case with two oil lines that allow non-forced free flow of oil between the rear case and front reduction gears,

In the 2910 and later model 2710, the PS return is forked so some of the oil goes to the reduction gears. One would presume this is to force some oil exchange between the reduction gears and the trans case rather than just rely on convection flow.

In general, it looks like there were a bunch of design mods made in the 2910 that we then rolled back into the 2710 beginning with SN 50101.

 

[kubmech]

Here you go wheeldog