I've got a 76y 953 that has a pretty significant transmission leak. Right now I'm losing about a gallon of fluid in a 10-12 hour period. It's coming out of the weep hole on the bell housing, and leaking out of the bottom of the bell housing. So I'm pretty sure it's the seal where the input shaft goes into the transmission. So my question is, how long can I continue to operate like this? I really want to get this fixed but I'd like to wait until winter time when I don't have as much work. But I'm just not sure if I might be causing unnecessary damage.
Something may be damaged that is causing the oil leak and further running the machine could result in a much more expensive repair. When I had a leaking wheel motor on my skid steer the hyd. shop said it's usually internal damage that causes the seal to leak. I replaced the motor because in most cases it's not cost effective to repair a drive motor and it costs $275 just to disassemble the drive motor. On a 953 I'd bet it's very pricey if you have to replace a drive motor or other trans. component. Better to investigate it as early as possible to avoid further damage or extra expenses.
When it runs out and something locks up is definitely too long
Thanks for the replies, I completely agree. I was really curious if anyone else has had a leak in the same spot on their machine and what they ended up doing.
As Welder Dave mentioned leaking seals is a symptom but not the cause. Worn bearings maybe the cause but running it to long will damage the shaft and that will be big bucks to fix or replace. The pump will have to be stripped so it's time to find someone with a lapping table so any scratch marks on the slippers, lenses plates and swash plate can be fixed. New bearings and seals could be the only items that need replacing .
I forgot to mention, I had the motor out last winter for a new rear main seal and fixing some leaks. I did change the outer seal on the transmission because I was right there. Up until this point, the transmission never leaked a drop but I was afraid if I didn't go ahead and change it, I'd regret it. When we put the motor back in, I had to have some help and I felt like we were a little rough with getting the motor back in, it's a really tight fit with the front engine mount. Shortly after this, the bottom of the bell housing was damp but I wasn't really losing much fluid so I put the belly pans back on and went to work. I worked all summer and would have to top off the transmission fluid every 40 hours or so but that was it until recently when it really started leaking. So that's what led me to believe it was most likely that seal giving out but I definitely agree that it could have been some bearing material or something taking it out. There hasn't been any unusual bearing noises or anything but that's obviously hard to tell on a running machine. Thanks for the reply.
The seal was more than likely damaged during installation of the seal, or during the install of the engine
Where the seal runs on the yokes, The wear groove will often start a new seal leaking. I have installed a super thin Speedy-Sleeve on many yokes when changing the seal. Also make sure the transmission breather is not plugged as the pressure will take the path of least resistance to leak out. Hope this helps. Simon C
Use of a Cat Seal installation tool keeps geometry of seal correct to shaft and housing, sets to correct depth, was one used here? Next up was alignment Engine to Pump Case checked as went back together, as running off align will eat seals.
That's what I was thinking too, and why I was less afraid to run it for a little while as is. I still really want to pull it out as soon as I can to figure out what's going on in there but didn't know how urgent I needed to be.
Good to know, that definitely helps. If I remember correctly there's an o-ring or two on the yoke that seals up to the seal on the transmission, is that what you are referring to by adding a speedy-sleeve or sleeving the yoke itself? I also didn't think to check the breather tube, I guess that could be clogged and could explain the sudden increase of fluid coming out?
No, I didn't use the correct tool. I just drove it in flush if I remember correctly. I should have definitely taken more time to do it right. I also did not realize you had to do an engine to pump case alignment, I'm going to look that up in my book, but do you have any tips for that?
Follow service manual guidance, easiest and less painful.
You can double check but I think I am right in saying that the Case Gp of the hydrostatic drive bolts direct on to the engine bellhousing using a ring of 12 bolts. In that case provided the bellhousing was pulled up snug there is no alignment procedure.
I was looking in my book this morning and it shows just driving in the outer seal. I was loading my loader on my trailer this morning and it was leaking worse than it had been so I'm going to start tearing into it this afternoon.
That's how I remembered it going back together but wasn't sure if I missed something. Now I'm trying to decide if I should pull the motor or pull the transmission, in case I have to pull the outer housing to work on anything further in the hydrostat.
I have found Vent Caps completely buried in dirt before. You need to find the vent if it has one. The speedy-sleeve is installed with loctite under it onto the yoke that is grooved. Have to push it in the correct distance so that the lip of the seal rides on the middle of it. I have installed a good number over the years. Easy to buy from a bearing supply store. You tube videos about how to install. Simon C
I glanced through the book yesterday to see if there was anything on a breather or vent and didn't find anything, I will look for one again on the machine. But that's a good idea for the sleeve, in case there's any imperfections on the yoke that might cause the original seal to leak.
So I've been thinking about this leak this weekend and I'm trying to figure out how I'm going to know if it's the outer seal only or if the leak originated in the splitter box? Does anyone know how to tell for sure? I assume the outer seal is really just to seal the oil bath bearing where as the inside is under pressure but that's just my guess for now. Maybe @Cmark can get in here and give me some pointers, I know he's really sharp on these.
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?
No. It probably got damaged when it was running misaligned.
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.
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.
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.
They are listed in catalogue which is a PDF and downloadable, page 370. You'll need the shaft diameter and number of splines.
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.
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.
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 ?
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.
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?
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.
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.