2910 Steering problem

[Alan L.]

My tractor is a 1999 model B2710HSD, serial number 11391. I bought the tractor in May of '99. Since my 2-year warranty will run out before the heat of next summer I am very concerned about the steering problem.

My problem was that my power steering pretty much shut down both directions in 98 degree heat mowing with a 5' rotary cutter in medium range. The heat guage never got over half-way, but usually runs way down in the cool range. I cleaned out the screen and the radiator itself but it didn't do any good. I spent 7 hours one day wrestling with the steering. I found that I could idle it down for a few minutes and the power steering would return for about 20 minutes, then it would act up again. Moving to low range helped the problem.

I had recently done the 50-hour service on the tractor myself, using super UDT. My dealer picked up the tractor and was able to duplicate the problem. They changed all the fluids again and stated to me that they had not fixed the problem and would be trying to get information from Kubota on the problem. I needed the tractor and they brought it back. I mowed with it the rest of the summer without problems, but it was never as hot after that.

This year I mowed with the cutter only once - back in May. I did not encounter a problem, but our summer was so dry I have not had any growth to cut since then, and have only used the tractor for light loader work and finish mowing the lawn. I have experienced only brief, isolated binding of the steering - but hard to duplicate.

I am not convinced the problem has really gone away and that my warranty will expire with the problem still lurking. I expect my tractor to last 20 years need to have this problem solved.

I was encouraged by the "fix" that has been posting on here and was planning on showing it to my dealer.

 

[hayden]

I'm still a bit confused about the oil filter(s) and strainers on the hydraulic circuits (not the HST circuit). I also have a theory.

The original 2710 WSM shows only a strainer on the suction line, and no filter at all in the steering/service circuits. The suction line is common to the steering and service circuits. The outflow from the steering circuit dumps right back into the suction line, and the outflow from the service circuit dumps into the trans case resevior. This is all prior to the addition of any "second filter".

The scan of the parts manual that someone provided shows the retrofit that was done to a 2710. The retrofit looks to me like it replaces the strainer and common suction pipe with a filter and new suction pipe presumably drawing oil through the filter instead of the old strainer.

I'm not clear on whether this is what's shipping in new tractors or not. Only careful tracing of the oil lines will tell. I'll check my 2910 and report back.

Why does this matter? Well, in the old strainer arrangement, the only filtering provided for oil passing through the steering and service pumps (and items they respectively power) is the strainer. If the strainer is inadequate, then crud could get into the pump and other equipment and cause damage. The replacement of the strainer with a filter appears to be an attempt to provide improved filtering on oil entering the pumps. This theory of crud getting past the strainer and doing damage is consistent with the observations, repairs, and resulting performance change described in the Kubota-mech note. No proof, just facts consistent with a theory.

I looked back at my 2400 WSM and see that it too draws oil solely through a strainer. So why hasn't this shown up on that family of machines? Well, remember the dual pumps in the 2910 and 2710, with one dedicated to the steering? Well the steering pump is a much smaller displacement pump than the previous single pump. Maybe the new smaller steering pump is more susceptable to crud that previously passed through the larger pump without incident?

People have reported particles totalling the size of a coin in their strainers when cleaning them, so there clearly is a presence of crud to cause such damage should it escape the strainer. High speed, sustained operation (the situation consistently associated with the problem) means max oil flow through the strainer and pumps, and highest probability of dislodging any crud. Dislodged crud causes pump damage and results in funky steering problem.

So, lets test this theory on people who have experienced this problem.

What maintenance schedule did you follow on your first oil changes etc.?

Did it include cleaning BOTH strainers? If so, how much crud was in them?

After the first strainer cleaning, have particles shown up again in the strainer, or were they only there in the first cleaning?

We still need to sort out the second filter on new factory shipments and confirm where in the circuit the filtration occurs.

Peter

 

[Bird]

Peter, I changed my hydraulic oil & filter & cleaned the two strainers at 46 hours. There were certainly some metal shavings on the strainers, but the shavings I got from both of them wouldn't have totalled a teaspoon full. And I haven't changed the oil or filter since, so I don't know whether there will be any shavings on the strainers next time. And I'm using UDT; not Super UDT oil.

Bird

 

[DaleW]

Peter,
I have a 2710 and have not experienced any of these problems. Changed oil and filters at 50hrs. Very very slight amount of metal in the strainers. Refilled with UDT and still no problems.
DaleW

 

[ronjhall]

Peter: After reading your message I got my parts list out. I did a couple of scans that show how the lines for the return run. It looks like the return line from the power steering goes to the front case of the trans. It still goes to the main return line also. I tried to trace the lines from the power steering pump but it is covered up by the panels around the steering. Any way look at these scans and see if it makes sense to you. I don't think the filter would be on the suction line. Every system that I have ever worked on alway has it on the return line. My tractor had my 50 hour oil and maintance done at 43 hours because of this problem. My dealer di not find anything in filters, oil or strainers.
ronjhall

ronh

 

[ronjhall]

Here is the other scan.

ronh

 

[hayden]

The parts scans show the pump and steering mechanism, but not the filter/strainer, so I think it's inconclusive.

I'm not sure a filter on the suction side is all that odd. It clearly provides maximum protection by only passing filtered oil through the system, where filtering on the pressure side leaves everything before the filter, including the pump, susceptable to damage. I checked and my backhoe, for example, filters on the suction line.

The parts post from an earlier thread on the 2710 shows the "modification" made to "Ian"'s tractor. It's identical to my 2910.

I just went out to confirm and my tractor is set up as foillows:

- The suction line for the HST has a strainer only and is on the left side. The line feeds directly into the pre-charge pump on the HST, which is consistent with the WSM drawings.

- From the charge pump, the oil flows through the oil cooler and then passes back through the filter for the HST (left side). From the filter it goes into the HST to do it's duty.

- There is NO strainer on the suction line for the service/steering pumps. The 2910 has only one strainer and it's for the HST oil pickup only. The service/steering suction line instead is attached directly to the body of the second filter housing (on the right side), presumably drawing oil through the filter.

- The diagram of the hydraulics in the 2710 WSM (page 3-M5) clearly shows that the 2710 has a different service/steering setup than what I've described for the 2910. The 2710 has a second strainer for the service/steering and no filter. This is what's been reported by 2710 owners.

- The parts drawings posted a while back shows the exact config that I have on my 2910, and also indicates that B2710 models beginning with SN 50101 are configured the same way (with a filter in place of the strainer).

So what does all this do to my theory? The only part that doesn't fit is the fact that B2910 owners who have a filter rather than a strainer on the suction line are still reporting the problem. This either means that crud is getting through the filter too, or it means that my theory is trash and I should go back to engineering high-tech products where I belong.

What am I going to do? I think I'll change my oil and filters at 10 hours then again at 50. I still quite frankly am surprised at the amount of metal particles reported in the strainers at the 50 hr service and would rather get that manufacturing crud out early before is has a chance to get free and do damage, because after all, I still believe my silly theory.

 

[ronjhall]

Peter: I don't disagree with your analysis of the system. Just find it interesting that an additional drain line has been added. Why? To help with the Power Steering, HST or both? There is another thread here where questions are being asked about trans noise. I have been a tractor owner operator since I was a kid; I'm well a wear of the noises that comes from a gear trans. The newer 2710's and 2910's do not have a hydraulic line running from the top of the rear to the front trans cases. The return line from the power steering seems to have replaced this. Also noticed front trans case parts that were changed in March and April of 2000.
Looks like I'm going to have too breakdown and putout the $100.00 plus for a WSM. I had one for my B7100HST and only used it one time in 15 years of owing tractor. But the parts list does not show flow or a complete assembly of all systems very well.
Using kub-mech"s report on how he repaired a 2710. I wonder if some other item such as pump, relief valve, or steering valve may have some internal damage.
This thread has been out for 3 weeks now. I have only seen 1 other 2910 with this problem. I'm hoping that the 50-hour service was required and my problem never shows up again. Warranty is still good for another 1½ years. I will be bush hogging about 2 ½ acres in the next week. Should get everything hot enough to checkout system.


ronh

 

[hayden]

Humm, I missed part of your original point about the plumbing.

When you say front trans case, do you mean the front axle or do you mean the front part of the rear assembly? What changed in the PS plumbing return lines?

I've got a B2710 WSM from 2/99. It does not cover the 2910 and the 2410. This is where most of my data is coming from. THere is a newer WSM that covers all tractors but I don't have it yet.

Anyway, the split return from the PS unit is shown in my older manual. Are you saying the split return has not always been there?

Sorry I'm being dense here. Can you explain again what the changes are that you've seen in the plumbing (aside from the strainer/filter part)?

 

[ronjhall]

Peter: I have a similar problem understanding things. That why these forums help. I'M referring to the transmission case not the front axle. Along with the filter strainer changes the return line from the Power Steering now goes to the main suction line and to the front trans case. In the scan powersteering1910.gif both the inlet and return lines are shown. The line just to the left and below 050-detail number is the new return line. In the Scan powersteering2910-1.gif, the new line is shown. I have included a scan of the old line that is not on newer 2710's and 2910's. Hope this clears up confusion.

ronh