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

 

[Wheeldog]

Thanks Kubmech/w3tcompact/icons/smile.gif. Sorry if I put you through the wringer to get there.

I haven't experienced the PS problem yet, and my mowing jobs usually take 1.5 - 2 hours at a pop. However, it has been a cool Spring to this point in CT, so the problem just may be waiting to show up at the same time as the hot weather.

Rob

 

[Wheeldog]

Kubmech,

I read through this thread after you bumped it to the top for me. I understand the gist of what you are saying, about the smaller reservoir in the PS circuit and the possibility of keeping too much heat in the fluid under certain conditions. You had said that the B24,27,29 all share the same (3.1 gpm) pump, but isn't the B2410's a lower capacity instead? (2.6 gpm PS / 4.4 gpm HST). I can't say as to how this would change things - smaller pump flow means less heat generated but smaller system volume (?) may make things worse? I just think its curious that we've only heard from one B2410 owner with this problem, and I know we have a few out there.

Rob

 

[ronjhall]

Wheeldog
Since I started this line. I thought I should respond on how my tractor is performing this year. I have not had a problem since transmission oil was changed last fall./w3tcompact/icons/smile.gif I haven't had to cut grass in temperatures above 80 degrees yet./w3tcompact/icons/tongue.gif I should get a chance this week. I will let you know how it goes after it is done. My dealer say that some of the 2710 and 2910 have had more than one oil change before problem goes away. These are tractors that are used by commercial owners.

 

[Wheeldog]

Thanks, Ron. We've got some 90+ F days coming by the end of the week, supposedly. I'm not overly concerned about the potential for a problem, just curious really

 

[kubmech]

Rob, I was informed that the flow rates in the manual "can't be right" when I asked the question. They should be 3.1 across the board. The 2410 pump is a different part number, that's why I asked the question, see my previous post in this thread(may have missed it). When I looked up the part numbers for the internal pump gears they were the same part number, which tells me, same size same flow rate. I kind of let it drop at the time, maybe when I get a chance I'll look into it more.

 

[Wheeldog]

Kubmech,

If you went to the trouble of looking up the part numbers of the gears then it sounds like you've already gone above and beyond the call. This is interesting to me first because I have a B2410 and second because I work for a company that designs and manufactures pumps (for aircraft, not tractors though /w3tcompact/icons/wink.gif). I agree that if the gear p/n's are the same that it should put out the same flow, unless the drive speed is somehow different or part of the discharge flow gets routed someplace else. I guess the answer lies somewhere in the difference between pump assembly p/n's.

Thanks for doing the digging. Meanwhile I have to go celebrate cause' my tractor just gained .5 gpm of pump flow/w3tcompact/icons/smile.gif.

Rob

 

[DarinRay]

Rob,

Congratulations on your new find. Hey that is quite a bit of improvement if you ask me. Here's an improvement for me too- my dump truck hyd pump had a pressure of 350psi and now just got a new pump installed after this one layed down and now I have 3600psi.wooooohoooooo /w3tcompact/icons/smile.gif

Darin

 

[Wheeldog]

Darin,

Congrats to you too. Sounds like you may have a catapult instead of a dump body now /w3tcompact/icons/wink.gif.

Rob

 

[ronjhall]

Rob
Well today was the first day over 80 degrees and had to cut the lawn./w3tcompact/icons/smile.gif Power steering started to act up again, just like last year./w3tcompact/icons/frown.gif Called the dealer. He is going to talk to <font color=orange> Kubota</font color=orange> and try to get a Field Service Tech out to look at problem. Will keep everybody up to date when problem is repaired.

 

[Wheeldog]

Ron,

Sorry to hear that the problem remains. I did some mowing last night - 2 hours straight in my neighbor's overgrown yard, and no sign of this problem on my B2410. The outdoor temperature was probably 75-80 F, so I don't know if this was enough of a test.

Good luck with your dealer and Kubota.

Rob