Hi all, I'm looking for ideas on what could cause the shaft splines on my hydraulic pump to shear twice in as many weeks. I bought this JD 310D this year and have only put about 20 hours on it (has about 4500). The pump went out at about 15 hours; turns out we had stripped the splines on the pump drive shaft. Had it fixed, and within 5 hours it happened again. So I'm wondering what would put that kind of shear force on the shaft. Reading around, possibilities seem to be cavitation due to a clogged intake screen, or fluid corrupted by dirt or water. But if anyone has seen this before or knows of other possible causes, I'd sure appreciate hearing it. Other info: I had the seals replaced on two of the cylinders after about 10 hours, and have replaced two leaky hoses. I also think the hydraulic pressure might be a bit low in general, as I can only pull both the boom and the dipperstick at the same time if I just pull slightly; otherwise only one or the other moves (or is that normal for this model?). I am about to have it fixed again, so any advice would be appreciated; don't want to strip the splines a third time. Thanks.
Did you replace the splined tube that the pump shaft slides into ? If you did, did you check them for fitment before reinstalling the pump ? Were all the bolts associated with the pump and the front engine mount tight ? There is an outside chance that one or both of the dowel pins is missing on the front engine mounting bolts. It is critical that they are both in place to maintain precise alignment of the pump and drive coupling.
That's a volume issue, but it's probably normal. The pressure is how hard it will pull. Could the hoe lift the machine off the ground? Somebody could have set the relief too high, say if the pump was failing and they thought it was the relief.
Like Tinkerer said, if the splines aren't new in the coupler, or if the pump to engine is misaligned. I don't know if this machine has a little short shaft or not, but if it does it could be bent. And, (now I'm copying Delmer) check the reliefs.
We did replace the splined tube, as that was actually the part that had sheared. We also replaced the flex coupling disk, since it was old. The fitment on the tube was very tight; no apparent movement. The two bolts holding all this to the engine were torqued tight. There didn't appear to be any place for dowel pins to secure the alignment of the pump; just two bolts and a flex coupling. Or you probably mean dowel pins at the engine mount itself; that is an interesting idea to check.
So you replaced the female splined tube, and the rubber coupling disk. How did the splines look on the pump shaft? and what stripped out the second time? Also what were the conditions when it broke each time?
The splines on the pump shaft looked good (the first time; I assume still true). I believe the pump shaft is a harder metal than the tube, so I expect to find the failure in the splined tube again. We will know for sure when we get the tractor into the shop tomorrow. The rattling noise sounds the same as the first time. Conditions at time of both failures: digging topsoil, no rocks, 22' wide, 18" deep, spoil to the right, backing up about 5' per strip.
Was it a John Deere part you installed? I have spent several hours today working on a brand new steering shaft for a **. My customer bought it online and it is made in Turkey. They turned the bushing journals and then broached the splines. The journals are .021 out of round.
Yes, authentic part, purchased from local Deere dealer. At least my wallet was a lot lighter afterward, so at least the price was authentic ...
The dowel pins are pressed into the block. They are an interference fit when the front engine mount is pulled over them when installing the front engine mounting bracket. The bore for the pump is precision bored at the factory for an exact pump alignment. That is why the dowel pins need to be in perfect condition and in place.
It looks like the problem stemmed from a faulty threaded insert in the pump mount. There are two inserts, which apparently aren't original equipment, and one has slipped out slightly. The theory is that it allowed enough pump movement to wear down a new spline shaft collar in just five hours. Apparently it was also like this before the first repair was done, and had been pressed flush with the surrounding metal and secured with dimples. So that didn't last very long. At this point, I would replace the pump mount, but it's not so easy to find one. The Deere parts catalog says it's unavailable, and to contact a certain vintage parts supplier, but they don't have it and neither do the used equipment yards the dealer has checked for me. Also, the spline shaft on the pump has been worn down to have a slight hourglass pattern; dealer says the pump should probably be replaced too (ouch $$). I'm interested in opinions here: Would you guys replace the pump? I'm sure replacing it is "best", but don't want to do that if fixing the mount would be sufficient. How would you fix the mount? We've discussed larger inserts, using a helicoil, and tapping new threads (would be a large diameter increase though). I'm attaching photos of the mount and the worn pump shaft. You can see the slight hourglassing on the shaft. Thanks for any advice you can give.
Yair . . . Colorado_ken . That looks to be a horrible set up. From the pictures it seems the pump relies on the bolts for alignment could that be right? . . . a more conventional arrangement would be to have the pump locating on a shoulder or spigot on the housing. With out knowing and seeing the full story I suggest the first thing is to get those thread inserts repaired properly by milling out and welding in some new ones. I would then bore out the mounting bolt holes in the pump flange to give a bit of come and go and spend some time mounting the pump with the bolts just nipped. Tap it around to get it as central in the bore as possible. On new components I would use a dial gauge but in your case with the worn shaft, a steel rule and a scriber will probably be as close as you can get. When you are satisfied its as good as you can get it torque those bolts down tight. Next stage is to get hold of a tapered reamer and I'd suggest about 3/8" matching pins. You may not be familiar with the technique as it is not used much these days in earthmoving gear but I believe still quite common in maintaining alignment in various marine and power station applications. The idea is that you drill a suitable sized holes at any old angle through both the pump flange and the mount, you then ream them out with the tapered reamer and hammer in the pins. The system has been around since the dawn of engineering and a quick Google should reveal a local source of a reamer and the pins. I'm sure other folks will have other ideas and that's the strength of this forum. Best of luck with it, I'm sure it can be fixed. Cheers.
Scrub Puller - G'day mate! Actually the alignment is provided by the pump sliding exactly into the large round hole on the mount - which means it should have stayed aligned pretty well even with one insert being loose. But I guess that small movement of the insert was enough to cause the problem, unless there's something else at work too.
I would check the drive part of the coupling that is on the engine damper for run out. Don't be too hasty and blame all of the problem on the pump mount.
Possible repair idea If it were mine, & since you can't readily get the part(s) ,I would take the mount itself off ,have the hourglass area built up(welded)@ a machine shop & turn it back to original spec's(if not too costly for you) & fix the threaded inserts , while out of machine. When re-installing, I would use slightly(1/2-5/8)longer mount bolts on pump,& put a nut on backside , so that it can't vibrate loose again. Just a theory,& possibly not useable in your situation. Good luck.
Tinkerer - It does seem the problem should be more in the area you mentioned. Are you talking about one of the parts on this diagram?
Hi Ken, I liked what Scrub Puller figured on how to go about fixing this. I'm focusing on the hole in the pump housing above the splines, I would believe if the pump was seated properly then you won't see the top edge of the bolt hole in the pump housing chewed up like the picture shows. If I'm seeing this right then more proof about what Scrub and everyone is saying. If you just bought the machine then the guy before you must have been going through the same thing.
I have a hard time believing the pump mounting bolts being out of alignment would do anything, unless the pump is obviously loose in the collar/sleeve. Did you look at the bracket to engine bolts (in post #10), check the torque even. Maybe put together a bracket on the crankshaft to use a dial indicator to check the bore alignment, in case the bracket got bent. I wouldn't hesitate to reuse the pump with the splines in that shape. Couldn't hurt to check the shaft for play, or bending. I'd replace #2 and #5 before I'd replace the pump, they're relatively cheap and wear out pretty fast when grit gets in the rubber and works away on the aluminum(?) I'd think if it was wearing out in 5 hours something is pretty messed up.
I would also pay heed to what that other feller said about a possible restriction or relief valve problem on the pump high side. That could restrict the volume (slow cylinder movements) and/or overload the pump causing the splines to shear, especially when the fluid is cold. Definitely get a gauge on that high side before you go much farther.
It looks like an aluminum mount that has thread insterts from the factory. Obviously they forgot the thread locker LOL The whole pump does not need to be replaced just the shaft can be. However there is still plenty of meat on there that I would not worry about it as you only put 50-100 hours /year that will go 20 years from an owner operator You really need to make sure the relief valve is set correctly. With a used machine you don't know the last "mechanic". It may also be scored and not opening fast enough. I believe this is also a piston pump so you may have a displacement control problem?? which would be protected by the relief anyways.
I think that same frame that the pump mounts to is the front engine support, so it better not be aluminum, but even cast iron could be bent. And that sure looks like a gear pump to me (and in jdparts).
Did you all happen to notice that the threaded inserts Colorado_Ken has holding the pump on are NOT in the JD drawing or the online parts book ? That machine obviously has had this problem for a long time. If the pressures the pump is putting out are within specs. I would be looking for a replacement front engine mount.
If that RH insert is holding the pump from seating back against the casting flat that would introduce a great deal of misalignment between the centerline of the crankshaft and the pump shaft centerline and the coupler cannot accomodate that much misalignment. I would take another posters advice and get rid of that inserts protrusion, if possible screw bolts through from the back and make sure the insert cannot pull front again, the bolt head against the casting. Check the pilot in the casting and the pilot on the pump. The shaft wear is not ideal but should not fail a new splined coupler on that short of a time frame. After the proper repairs are made and alignment checked and verified install the pump with Molycote or a similar moly based spline lube.
Did you find the answer to this problem?
Thanks for asking; sorry I didn't reply sooner. Once we got the backhoe working, my attention went elsewhere. The repair job has been working okay so far, but I suppose it ought to, because we ended up replacing both the pump mount and the pump. We did find answers to the various suggestions that everyone offered, and everything checked out okay. The dowels were not missing between the mount and the engine, and the relief valve pressures tested okay. Since the threaded inserts were known to have shifted a bit between repairs, everything pointed to them as the main problem. Actually, I suspected that just replacing the mount would have been enough, without replacing the pump. But when I compared the worn spline to one on a new pump, the difference was enough that I decided not to take the chance. I had also hoped that a new pump might produce more flow too, but I didn't notice any difference in operation, so I suppose the old one had plenty of life left, aside from the worn spline. So now I have a spare old pump that I will probably never use (I hope). By the way, the mount wasn't easy to find; new ones aren't available any more, and we had to search out of state just to locate a used one. On the bright side, I suppose I've learned at least one lesson from this experience: when I crack open the piggy bank to buy an old machine, that's not likely to be the last dollar I'm going to spend on it...
Thanks for coming back and posting the final results for the problem. I am sure that I am not the only one that wondered what you did to fix it. You did the right thing when you replaced the pump. A worn spline will eventually fail at the worst possible time.