955L transferring fluid from transmission to bevel gear case

[leadfarmer]

I decided to make this a new thread for the purpose of future people searching this topic, so more people see it, and because my other thread is on various topics.

Caterpillar 955L SN: 85J10466

Alright, back to the oil level issue that I thought was myself incorrectly adding fluid to the bevel gear case instead of the transmission.

After some more hours of seat time, I can confirm with certainty that the transmission fluid is transferring to the bevel gear case. It is doing so at a fairly high rate. Several gallons over a few hours.

I have been removing oil from the bevel gear case through the filler tube and adding fresh fluid to the transmission so I can accomplish the work I need to get done. I need to finish a few more projects and then I will have some downtime for a repair.

I did some more research and found several other places saying the steering clutch pump can suck oil out of the transmission if the pump seals are bad or the steering clutch oil screen is clogged. Here is one: https://www.yesterdaystractors.com/cgi-bin/viewit.cgi?bd=crawlers&th=53142

Is it worth checking the steering clutch pressure to try and confirm this? It sounds like the steering clutch pump is getting fluid one way or another if the seals are bad. I also read in the service manual that the fluid pressure won't be at maximum condition unless the clutches are new. Given that the steering clutches function without issue, I'm guessing there isn't much value in checking the pressure.

I will pull the steering gear oil screen again and clean/inspect it first.

How difficult is it to service the steering clutch pump? Any tips and tricks for removal, overhaul, and re-installation? I didn't find anything in the 85J 955L service manual I have about servicing this pump.

If it ends up that the actual problem is the pinion seal leaking directly between the transmission and bevel gear case (multiple sources say this is unlikely to fail) then I will just have to live with it and keep playing the oil shuffle game as I am not up to pulling the transmission at this time or in the near future. A few gallons of oil will just be the cost of getting work done. Given the high rate of fluid transfer, that makes me suspect the issue is with the pump rather than the pinion seal.

 

[leadfarmer]

No one has any thoughts on this conundrum?

 

[DMiller]

Not gonna like them. Strip and reseal is Only alternative.

 

[kshansen]

Not gonna like them. Strip and reseal is Only alternative.

Not familiar with the 955L but unless I'm not looking in the wrong place on SIS I'm not seeing how a pump seal would get oil into the bevel gear case. don't the pumps drive off the converter housing? Maybe I'm just thinking about how I recall a D6C being set up somewhat similar to a 966C?

 

[leadfarmer]

I think I need to check my transmission pressure after reading this thread: http://www.acmoc.org/bb/showthread.php?4448-Cat-955L-won-t-push-under-heavy-load/page10

I definitely have these issues:

1. Some fluid leaking into the belly pan. Previous owner welded my belly pan on so removing it to clean out and inspect is not something I can tackle anytime soon. Does anyone know more about why and from where the torque converter leaks?

2. Tracks won't spin all the time when I'm pushing into material. Seems like when the machine is between cold and top operating temp it will keep spinning the tracks while pushing but once it gets warmed up completely they will stall.

3. When the machine is warmed up from use, turned off, then restarted (while still warmed up) it takes a few minutes for the machine to move, like it needs to build up pressure. It will start to move slowly and then after a minute or so it's back to moving around just fine.

I am still maintaining fluid levels and using the machine because I have a tight schedule to get dirt moved for a new barn. Once that is done I can tear into it.

 

[kshansen]

I think I need to check my transmission pressure after reading this thread: http://www.acmoc.org/bb/showthread.php?4448-Cat-955L-won-t-push-under-heavy-load/page10

I definitely have these issues:

1. Some fluid leaking into the belly pan. Previous owner welded my belly pan on so removing it to clean out and inspect is not something I can tackle anytime soon. Does anyone know more about why and from where the torque converter leaks?.

Dam PO's!

Someone like that should be shot for doing that! Not killed just shot enough to cause major pain! Then they should be made to remove the pans with machine parked in a manure pit!

As for why and where oil could be leaking that is a tough one to say. Could be any place from a mounting oring, suction hose, pump housing or seal and so on guess it boils down to any place where there is oil inside that is getting outside. Seals hoses, gaskets crack in a housing, loose bolts...................................................

 

[leadfarmer]

Reading that thread on ACMOC it sounded like the torque converter had a designed means of intentionally leaking, but maybe I misunderstood that.

 

[kshansen]

Reading that thread on ACMOC it sounded like the torque converter had a designed means of intentionally leaking, but maybe I misunderstood that.

Could be something in the terminology someone is using. Maybe something like a hole somewhere to vent off trapped air? But I would have to read that thread to see if it makes any sense.

Well did not read 1005 of the 96 post there but did see this remark in one of them:
"A cat torque leaks about 2 GPM so if you get more than half a pail you have trouble."

As I read that it's just saying that the converter leaks that much oil into the converter housing and it drains back into the transmission. It would not be going into the bevel gear housing,

I'm attaching the Systems Operation manual for the 955L might be some information there that will help.

 

[kshansen]

One more attachment:

This one is from parts book on the 955L, if you look at the gear there is an oring #27 that appears to seal the pinion shaft to coupler #9
and there are also two lip type seals #16 that seal the transmission end of the coupler. Just looking at that drawing I could see where either of those two places could be a source of transmission oil getting in to the bevel gear housing. Neither of which look to be an easy repair to make.

Also one could find that the reason one or both those sealing points could be leaking due to problems in any of the bearings or other parts in that picture!

 

[leadfarmer]

To update this thread:

I happened to meet a local fellow who was very experienced with 955L ownership. He had a 955L that was doing the same thing with fluids. He said the steering pump was sucking fluid from the trans pump, so that is the third place I had gotten that explanation for fluid migrating from the trans to gear case.

I checked the trans and gear case screens and found nothing.

I removed the steering pump and it had no concerning wear. Resealed and re-installed.

I removed the transmission pump and it was worn to the point of needing replacement. Replaced it with a CGR made aftermarket pump from Amazon (12 month warranty). Photos in post #174 here: https://www.heavyequipmentforums.com/threads/happy-new-955l-owner-with-questions.80272/page-9

Assembled both pumps with lucas engine oil additive (very thick and tacky) and then primed both pumps for start up through the pressure gauge ports with the same oil.

No issues running it for a few hours of stump removal.

Now to get back to serious earth moving this spring and see what happens with the fluid levels.

Tip for anyone changing the pumps: there are more bolts than the CAT service manual showed. A cruel joke. I think 3 on the steering pump and 4 on the trans pump. The 4th bolt on the trans pump will require you to tackle it from below using a variety of extensions, a wobble joint, and a crow's foot. It was hell. I see now why "some guys leave that bolt out" but I had to put it back in and declare victory.