Gary Sweat
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I looked at the breakdown and have a question. When the seal moves, does the shaft (7) also move out a little bit?
JD 855 Transmission Seal Leak
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I looked at the breakdown and have a question. When the seal moves, does the shaft (7) also move out a little bit?
Mechanos
Veteran Member
It should be able to, Gary. The u-joint that splines onto this shaft is the split design that has as pinch-bolt to lock the yoke to the shaft. Since the other end of the d-shaft is bolted to the flywheel, there shouldn't be any way that the shaft can move.... unless the u-joints are totally shot.
Mechanos
Veteran Member
Kind of sounds like one of the relief valves on the hydro trans unit is sticking and causing the trans to over pressurize. This could explain the randomness of when the seal decides to blow out.
Gary/Mechanos, correct, the shaft does not move laterally since it is prevented by the splined shaft that is a direct connection to the flywheel. The only solution that remains is for me to spring for the parts from JD since the housing it shows has a groove for a retaining spring clip. Since I am not overpressurizing, it stands to reason that the new parts SHOULD solve the problem. A bummer at $300 to keep a $7.50 seal from blowing. Have checked the vent tube and there are no obstructions. I also ran for awhile with the filler cap almost completely removed (to eliminate overpressure) to no avail. It still blew.
Gary Sweat
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I don't think in this case, removing the filler cap will have an effect on relieving pressure behind the seal. If pump pressure is putting pressure on the seal, it will still be there even if the cap is open.
Has the tractor always had this problem? I ask because it it didn't, then a snap ring will not fix the problem, only change it to a different problem. The reason the seal is being pushed out needs to be found and corrected. This type of seal is made to fit pretty tight in the housing and usually takes some effort to remove them. They are not designed to hold back pressure, only act as a wiper seal for oil that gets onto the shaft.
Mechanos
Veteran Member
I agree with Gary. There is no filler cap or vent tube on the transmission, anyway. The vent tube and filler cap at the rear of the tractor is on the transaxle which is nothing more than a reservoir to hold the oil that the transmission's charge pump suck up and sends through the transmissions circuits. There is something not right in your transmission. You can't make it going away by putting a snap ring on the seal.... you need to identify what is causing the transmission to intermittantly overpressurize and blow the seal and fix it. I'm still leaning towards a relief valve that is hanging up.
dfkrug
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I have parts diagrams from my 955 projects, and you definitely have to
have a snap ring to hold the seal in there (item #61). Maybe your
groove is there, just filled up with detritus?
If it is easy to get the new seal in there, it is not going to take much for
it to work itself out.
What is costing $300?
Gary Sweat
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Goes back to my question of "has it always popped out" or did it just start lately. There may have been two types of seals (possibly a mid model change), one that fit very tight (like axle seals) and one that doesn't fit tight and needs the snap ring. Could be there is an older style seal that is not showing up in later drawings or parts manuals.
David-Davies
Silver Member
Sorry but I too thought that you were talking crank shaft front seal. Your broblem has nothing to do with vents or caps. Your seal is poping out from a lost snap ring, or over pressure, or your pump needs a rebuild, as it is leaking pressure internally. I'd would start looking at the pressure relife, for sticking, foreign material, scoring, rust, ect. pressure test for proper opening, pressure.
Dave
Dave
Hi all, I just joined this site after finding this thread in a web search.
My JD 855 has a similar problem, it blew out the front hydrostatic drive input seal, first noticed while plowing snow, backed up and noticed a trail of brown/yellow leakage on the ground. I have had the tractor since 1993 but bought it used, so it is probably about a 1991 model. Still shows under 600 hours for a 20 year old machine but is kept outside and uncovered so shows some age. I use it to mow with a 60" belly deck in summer, to plow with a 5' snow blade (JD 380) in winter, and occasionally run a brush hog (JD 403). All those attachments came with it as a package deal, then I added a no-name back blade for spreading driveway gravel.
So back to the seal - it popped while plowing the Groundhog's Day blizzard. It was a few days before I finally had time and warm enough weather to start trying to find the source, but it ended up being that front seal which was sitting cockeyed in the housing. I thought it would be an easy fix to simply tap it back in without tearing it apart much, so with the input shaft still connected, I used a socket extension as a punch to gently tap it back flush, working my way around the edge that was pushed out. As you might guess, that didn't hold for very long, I plowed for maybe 15 minutes before it started peeing hydro fluid again (don't eat yellow snow :licking: ).
So now I'm looking at this thread and see the talk of the snap ring, #61 in this diagram:
But like the OP, I don't think mine has that snap ring and if it did, wouldn't I have likely found the ring captured by the input shaft? Unless it broke in half and fell away in sections?
But my real question is about removing the driveshaft from the input shaft. I know that at minimum, I am going to need to replace the seal. So to do that, I will have to remove the coupling shaft which is connected via the U-joint to the driveshaft. There is no sliding expansion section like a car driveshaft (or the driveshafts on my mowing deck and brush hog), so I am wondering if I need to unbolt the front of the driveshaft from the engine flywheel and work the U-joint around to where there will be enough clearance to pull the whole assembly away from the hydro input shaft? Or is there not even enough clearance at the flywheel to get the front free? In which case, it looks like the only way to get it out would be to press apart the U-joint?
We've had so much snow this year that I'm running out of room to put it and both times the seal popped, it was while slamming the front blade into a relatively immobile snowbank. That's not a new practice for this year, I've always been pretty rough on it while plowing. So I'm wondering if that impact force might have, over time, translated from a longitudinal force to a slight lateral force at the input of the hydro to the point where it eventually wobbled the seal enough to loosen it up and now it just won't hold. I guess I won't know for sure until I replace the seal and then find out whether I have an over-pressure situation like the OP, or whether I'll be good for another 20 years of plowing.
Thanks for any insight!
My JD 855 has a similar problem, it blew out the front hydrostatic drive input seal, first noticed while plowing snow, backed up and noticed a trail of brown/yellow leakage on the ground. I have had the tractor since 1993 but bought it used, so it is probably about a 1991 model. Still shows under 600 hours for a 20 year old machine but is kept outside and uncovered so shows some age. I use it to mow with a 60" belly deck in summer, to plow with a 5' snow blade (JD 380) in winter, and occasionally run a brush hog (JD 403). All those attachments came with it as a package deal, then I added a no-name back blade for spreading driveway gravel.
So back to the seal - it popped while plowing the Groundhog's Day blizzard. It was a few days before I finally had time and warm enough weather to start trying to find the source, but it ended up being that front seal which was sitting cockeyed in the housing. I thought it would be an easy fix to simply tap it back in without tearing it apart much, so with the input shaft still connected, I used a socket extension as a punch to gently tap it back flush, working my way around the edge that was pushed out. As you might guess, that didn't hold for very long, I plowed for maybe 15 minutes before it started peeing hydro fluid again (don't eat yellow snow :licking: ).
So now I'm looking at this thread and see the talk of the snap ring, #61 in this diagram:
But like the OP, I don't think mine has that snap ring and if it did, wouldn't I have likely found the ring captured by the input shaft? Unless it broke in half and fell away in sections?
But my real question is about removing the driveshaft from the input shaft. I know that at minimum, I am going to need to replace the seal. So to do that, I will have to remove the coupling shaft which is connected via the U-joint to the driveshaft. There is no sliding expansion section like a car driveshaft (or the driveshafts on my mowing deck and brush hog), so I am wondering if I need to unbolt the front of the driveshaft from the engine flywheel and work the U-joint around to where there will be enough clearance to pull the whole assembly away from the hydro input shaft? Or is there not even enough clearance at the flywheel to get the front free? In which case, it looks like the only way to get it out would be to press apart the U-joint?
We've had so much snow this year that I'm running out of room to put it and both times the seal popped, it was while slamming the front blade into a relatively immobile snowbank. That's not a new practice for this year, I've always been pretty rough on it while plowing. So I'm wondering if that impact force might have, over time, translated from a longitudinal force to a slight lateral force at the input of the hydro to the point where it eventually wobbled the seal enough to loosen it up and now it just won't hold. I guess I won't know for sure until I replace the seal and then find out whether I have an over-pressure situation like the OP, or whether I'll be good for another 20 years of plowing.
Thanks for any insight!
