7117 Transmission Leak

[Snojetter]

This may be too broad of a question, but I'll try casting the line anyway and see what happens.  I just purchased a 1989 7117 that has a leak in the transmission somewhere.  The machine is fairly clean - the hydro and transmission final drive/gearbox are not completely caked with grime as I've often seen.  But there is some grease and chaff build-up.  I can't pin-point the location of the leak exactly.  I can see where the drip is collecting at the bottom of the transmission, but there isn't an obvious stream of oil leading to a seal or gasket that I can see.  Are there some typical locations that spring a leak on these tractors?  Is there a method to finding that elusive leak you've used successfully?  Does the leak tend to show itself more while in operation (under pressure)?

Do the hydro and transmission gearbox have separate oil reservoirs?  In other words, will a leak in one affect the other?

Kyle Sands <>< Brandon, MN

[Tom45]

The hydrostatic and transmission are one single reservoir.  There should be a spring loaded vent on the left side that must have the small plunger pulled up when the oil level is checked or filled.  There is a center gasket on the transmission case, a seal on each side axle shaft, a seal on the brake shaft, and a seal on the hydrostatic input shaft and opposite at the charge pump side. 

Tom

[Brettw]

Usually a good cleaning and degreasing / washing will expose where the leak may be coming from.  If it's a weep vs. a gusher, I wouldn't be overly concerned.

[Snojetter]

Ok, that's good news there isn't a huge number of places for the leak to be originating from.  I can eliminate the axle seals, so that narrows things down further.

What would constitute a "gusher?"  I'd say I lost a couple ounces over the 4 day weekend when I parked it.  There was a large wet spot under the transmission, but no thickness to the film of oil.

[ShaunE]

Even though there was no thickness to the oil on the floor, check the level in the BGB to be on the safe side.  Also, if the BGB is the culprit on either of the driven shaft seals, you may have a definitive oil spray line on the underside of the seat pan.  It will become apparent where the leak is once it is degreased & clean.

[george116]

12 hours ago, Snojetter said:

What would constitute a "gusher?"  I'd say I lost a couple ounces over the 4 day weekend when I parked it.  There was a large wet spot under the transmission, but no thickness to the film of oil.

I had a leak from the input shaft seal on mine.  It did not leak while sitting unused -- part of the reason being that the fluid level I don't think is high enough while it's not under pressure.  I bought it with a small leak (based on oily grimy buildup in the area) that eventually turned fairly significant with one season's use.  I think I was losing about 1/3 quart every time I mowed my acre of yard.  It got to the point where I had to fix it because I was worried the seal was going to lose all integrity while in use and then I'd have a worthless transmission if it put all the fluid on the ground.

So since yours is leaking while just sitting there, I'd guess that it probably isn't coming from the input shaft seal.  As high up as that seal is, I would think you'd be able to see evidence of the leak on the parts of the case in that area if that was the culprit.

[PhanDad]

BGB fluid level is tricky. 

Many people overfill them and they blow fluid when running.  On the opposite end, since the fluid level isn't the easiest to check, many times they are run low on fluid and the roller bearings fail and take out the seal, usually the front first .  I've seen the front shaft bearing completely go and the shaft rotates eccentrically and take out the case.

[Snojetter]

The leak isn't coming from the BGB.  That unit is dry as a bone...on the outside.  But that was a good reminder to check the fluid level.  I found the oil was low, so caught that before anything catastrophic occurred.

I don't know that the transmission/hydro leaks while sitting idle.  This was a purchase I made just last week, so I have no experience with it.  I drove it around the yard for about 20 minutes before parking it in the shop and I later found the leak.  So it certainly could be that it leaks when running/under pressure.  I wiped the bottom of the case dry and moved it to a clean spot on the shop floor; I'll find out tomorrow if it's a static leak.

I also did a little more reading on this site and discovered that the relief valve could be an issue.  I pulled that fitting off and found that it was stuck (couldn't pull it free when grasped between my fingernails).  When I pushed the valve from the underside, it popped free quite easily.  But I really pulled on it from the top and it wouldn't move so it seemed genuinely stuck.  I guess I'm not really sure about whether or not that may have contributed to the problem.  I'm letting it soak overnight to make sure all the grime is cleaned off.  If I find oil on the floor tomorrow, it's safe to say there's another issue beyond the relief valve.  If the floor is clean, then I'll reinstall the valve and take the tractor for another joy-ride to see if the leak reappears or not.