JD 855 Transmission Seal Leak

suchaski · Feb 19, 2011

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?

David-Davies · Feb 19, 2011

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 · Feb 20, 2011

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?

suchaski · Feb 20, 2011

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 · Feb 20, 2011

suchaski said:
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.

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.

suchaski · Feb 20, 2011

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 · Feb 20, 2011

suchaski said:
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........

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 · Feb 20, 2011

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?

suchaski · Feb 20, 2011

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)

Gary Sweat · Feb 20, 2011

suchaski said:
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)

Disregard what I said. I too thought you were talking about the front seal.