How long is too long to run a leaking hydrostat main seal on 953?

[joshbowling45]

The splitter box and pump case share a common oil supply so the transmission input seal is sealing in case pressure only. There is no breather on the transmission case, only the flywheel housing. Unless there is some physical damage to the case, the leak can only be from the seal or the O ring on the splined shaft from the drive coupling.
When you take it apart, check the input gear for excess play. There should be about 0.015" endfloat.
If you think the seal is running on a worn portion of the shaft, you can drive the seal in a little further.

*Edit*
This the one where the housing got broken, right? You should also check if the input shaft and flex drive coupling are running true.

Okay good to know. I think when I changed the seal the last time I forgot to get the o-rings for the coupler, that could very well be where this leak is coming from. And yes it is the same one. I will definitely check that, I assumed they were running true because previously it never leaked from the transmission, I only changed the seal as a preventative measure. I also remembered that the splined shaft seemed to have a fair amount of wear on the splines, is that normal?

 

[Cmark]

the splined shaft seemed to have a fair amount of wear on the splines, is that normal?

No. It probably got damaged when it was running misaligned.

 

[Tones]

There is a company here in Australia who sell spline shaft ends (Southcott) for hydraulic pumps and motors which are welded onto the original shaft. There maybe a business in the States who does the same. As to the viability of doing this I'll leave that to the guru's here to comment on.

 

[joshbowling45]

No. It probably got damaged when it was running misaligned.

That's what I was afraid of. The good news is the engine stayed bolted up tight, no problems there. I'm hoping to have the motor out tomorrow afternoon, I'll get some pictures of the coupler and see what's going on in there. Really making me consider getting a new coupler just to be safe.

 

[joshbowling45]

There is a company here in Australia who sell spline shaft ends (Southcott) for hydraulic pumps and motors which are welded onto the original shaft. There maybe a business in the States who does the same. As to the viability of doing this I'll leave that to the guru's here to comment on.

Interesting. I will do some checking on that, but I might just try to come up with a new coupler. I'm actually going on vacation to Australia here in a couple months, might have to just bring one back with me. Haha.

 

[Tones]

They are listed in catalogue which is a PDF and downloadable, page 370. You'll need the shaft diameter and number of splines.

 

[joshbowling45]

I've got the motor out and after closer inspection, I think it was the o-ring that was leaking. It looks to have a flat spot on the o.d. The input seal could have possibly been leaking as well, I don't think I drove it in far enough the first time around, I think it was sitting just on the inside of the tapered part of the shaft. I attached a picture of the drive shaft, it actually didn't seem to have as much wear as I thought, I still need to verify that it's running true, not really sure how to check that though? I did go ahead and order the flex drive coupler to bolt to my shaft, don't want to put this back together for that to give out. I also figured out that for the early model 953s, in order to pull the motor out, you have to pull the oil pan off while it's still in the machine or it won't hardly clear the motor mount. That's why we had a hard time getting it back in the first time around. They must have updated the design thankfully because pulling the oil pan off to expose the bottom end of the motor to all the nasty grime is a terrible design.

 

[Nige]

Would you like to post up a better close-up photo of the shaft splines. When I enlarge the image they look awful worn to me, and in a weird wear pattern, but maybe the photo is deceiving.

 

[joshbowling45]

Here's a couple better pictures. The shaft definitely has some wear, don't get me wrong. But it probably looked worse in the previous picture because I hadn't cleaned it off yet. I priced a new shaft from CAT and it's $1300 bucks, plus $450 for the flex coupler. I did go ahead and buy a new flex coupler because the rubber bushings were starting to show some cracks and I'd hate for that to go out and have to pull the motor back out. But I'm pretty sure my leak was coming from that old yellow o-ring, I put my new o-ring on the shaft and you can tell a major difference just sliding your finger across it. I went ahead and slid it into the input gear on the transmission, and you can feel it seal up. Only issue that has me a little nervous is with the wear on those splines, there is a little bit of play from the flex drive coupler shaft into the input gear. I think it will be alright, I think the flex drive coupler itself actually is engineered to have some flex? But I can't say that with certainty because this is the only machine that I have any experience with. Any ideas @Cmark and @Nige?

 

[Cmark]

There will certainly be a bit of give in the flex coupling. I would still be checking the shaft though. Do you have access to a lathe where you can mount it in the chuck and check for runout with an indicator?

 

[joshbowling45]

There will certainly be a bit of give in the flex coupling. I would still be checking the shaft though. Do you have access to a lathe where you can mount it in the chuck and check for runout with an indicator?

I chucked the shaft up in the lathe, on the splines and spun it around and set the bit on the plate that bolts it on to the coupler and spun it around. It's definitely running true, I only had the slightest variance but that is most likely from the splines being a little worn. There was a centering indention that I could have used, but I felt like the splines were a better indicator of the condition of the shaft because if the wear on the splines were causing it to run egg-shape then I'd know where as the centering ring would be true regardless unless the shaft was bent really bad. I got the motor slid back in today after fixing a bunch of other shoddy mechanic work done by someone along the line. Someone twisted a bolt off in the injector pump, then drilled it out, put a 9/16 keensert threaded insert, then crossthreaded a metric bolt up that. All while managing to break out the channel that an o-ring sits in from the injector pump to the oil manifold. Then for the grand finale, they smeared gasket maker all over the face of the housing and bolted it back up but since that channel was broken, the o-ring smashed out and tore. What a mess. But anyhow, I've still got to finish bolting it up, torquing everything, and putting everything back on but I think we should be in good shape. I will update after I run it for awhile.

 

[joshbowling45]

Well so far so good. I've got about 12 hours on the machine and haven't lost any fluid so I think we are good. This is a pretty good old loader outside of the issues I've had, the engine doesn't use a drop of oil in 200 hours and it'll spin the tracks on a hard push, it has really good power in my opinion but I've never ran a newer machine. I've got new pads and rails on it and pretty much all new drive hoses, a whole bunch of hoses for the loader. But I've got a chance to trade up for a real nice 953B, has all the factory books and maintenance records, apparently has been a one owner machine before making it's journey across the country. I'm having a hard time making the decision because I've done so much work to mine and I feel like it's a good machine, just old and has the old machine problems. So I don't want to buy something and have to start over going back through everything. But the clean 953Bs are getting really hard to find so I'm really considering going for it. I know it's unrelated to the original topic but anyone have any suggestions for me?

 

[Tones]

Ask yourself, will the newer machine work any better than your current one? All the other questions you have already answered .

 

[joshbowling45]

Ask yourself, will the newer machine work any better than your current one? All the other questions you have already answered .

Well that's what I'm not sure about. Was curious if anyone else had upgraded to a B model and if it was worth it in terms of reliability and performance. I'm pretty happy with mine but I do work on it alot, would be nice to have a more original machine with less hours. More time in the seat making money instead of time with wrenches spending it. Lol.

 

[Welder Dave]

How many hours on the B? Has it had oil samples taken at regular intervals? It might help tell you if it could be a great machine or a few hundred hours away from needing some major repairs. If you could do blow by and other tests on the engine and drive train such as pressure checks would be great for helping to determine the life left in it. Just being lower hours doesn't relate to better condition.

 

[joshbowling45]

How many hours on the B? Has it had oil samples taken at regular intervals? It might help tell you if it could be a great machine or a few hundred hours away from needing some major repairs. If you could do blow by and other tests on the engine and drive train such as pressure checks would be great for helping to determine the life left in it. Just being lower hours doesn't relate to better condition.

I did some oil samples on the last semi I bought and was really glad that I did, gives some piece of mind. I don't know for sure, I haven't went and looked at it yet, this was purely testing the waters to see if anyone thought upgrading to a B was well worth it over a known A model. I'm probably leaning more towards keeping mine, but the thought of a more original machine is definitely tempting. Almost everything that I've had to fix on mine has been something that was repaired incorrectly and that gets aggravating after awhile.