Help! I love my JD 855 but am having a problem with the front shaft seal where the crankshaft hooks up. The seal is pressed into the front of the housing and I have blown this seal right out of the case three times. There is no rhyme or reason I can figure. Today it blew out again while trying to get ready to do a controlled burn. Had to get it out of the woods before I could do anything. I have bought two new seals and replaced them. There is no groove in the housing for a snap ring and John Deere says it doesn't require one. I am at a loss, and so is the John Deere dealer I get my parts from. Any Ideas?
JD 855 Transmission Seal Leak
- Thread starter suchaski
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David-Davies
Silver Member
Hello suchaski. I'm not really familler with J-D. Whenever I've had a seal that blowes out, it's usually from excessive internal pressure. Your positive crankcase ventulation may not be working. I'd remove the oil fill cap and see how much air [blow by] you have comming out.
Gary Sweat
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I am not familiar with this particular engine but most engine front seals work the same way. It sounds like oil pressure is building behind the seal from the front main bearing and can't get back quickly enough to the oil pan. I would look to see if the oil drain hole just behind the seal is blocked.
Is there signs of oil leaking from the seal before it gets pushed out of the housing?
Is there signs of oil leaking from the seal before it gets pushed out of the housing?
I am checking out the vent on it this morning. I am not sure but I think it is the tube that is an upside down "U" shape on the back by the fill hole. As far as leaking before it blows, there is no indication what so ever. I can say that in one of the previous times before I bought a new one, after pushing it and cranking up, as rpm increased you could watch the seal creep out of the retainment.
Gary Sweat
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The seal should take a bit of pressure to get it into the housing. Usually done by tapping it in with a hammer and piece of pipe or something the size of the outside of the seal. If it goes in by hand pressure alone, the seal is not the correct size.
Ok, so I checked the vent tube...all clear. Even took the fill cap and loosened it to see if that would have any affect. No Joy....blew the darn thing again. I have put two new seals in it that were ordered from JD (took forever to get them each time). When installing I used a socket the circumference of the outside edge of the seal to push it in. Only took mild tapping with a mallet to seat it each time. Just looked up the parts on JD, and there is another housing that DOES have a seat for a snap ring. Wow, $300 worth of parts to fix this problem. Oh well, I am at my wits end........
Gary Sweat
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I would be concerned about what is pushing the seal out. If the seal fits pretty tight in the housing then either oil is getting trapped behind the seal and the 50psi or so from the oil pump will build up. An overfilled crankcase can sometimes cause front seal leaks but I don't recall ever seeing it put enough pressure on them to push one out. If the seal fits too loose, the spin of the crankshaft can walk it down the shaft.
Those type of seals usually take a fair amount of prying to get them out of the housing.
Mechanos
Veteran Member
OK.... I'm confused. You say transmission in the title of the post, then you're talking about the crankshaft (which is in the engine), bunch of people here are talking about engine related causes, then you're talking about checking things on the transaxle. Just what seal is it that keeps blowing? Engine seal, transmission seal or transaxle seal?
The seal for the front of the input shaft to the hydrostatic transmission. On the 855 there is a drive shaft from the flywheel that splines onto the input shaft of the transmission and hydrostatic pump assembly. It is the seal that is on the front of this hydrostatic pump that keeps blowing. It is item 44 on this breakdown: John Deere - Parts Catalog
I saw earlier that on this one there is a snap ring and my housing does not have a groove for the snap ring (61)
I saw earlier that on this one there is a snap ring and my housing does not have a groove for the snap ring (61)
Gary Sweat
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Disregard what I said. I too thought you were talking about the front seal.
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?
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!
