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

[joshbowling45]

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.

 

[Welder Dave]

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.

 

[Vetech63]

When it runs out and something locks up is definitely too long

 

[joshbowling45]

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.

 

[Tones]

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 .

 

[joshbowling45]

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.

 

[Vetech63]

The seal was more than likely damaged during installation of the seal, or during the install of the engine

 

[Simon C]

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

 

[DMiller]

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.

 

[joshbowling45]

The seal was more than likely damaged during installation of the seal, or during the install of the engine

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.

 

[joshbowling45]

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

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?

 

[joshbowling45]

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.

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?

 

[DMiller]

Follow service manual guidance, easiest and less painful.

 

[Nige]

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.

 

[joshbowling45]

Follow service manual guidance, easiest and less painful.

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.

 

[joshbowling45]

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.

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.

 

[Simon C]

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

 

[joshbowling45]

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.

 

[joshbowling45]

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.

 

[Cmark]

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.