Seal blowby update

[Oaf]

I did what Texas! suggested and drained the trans to the level hole and ran it for a while. 3/4 quart came out, which is odd because I filled it to spec when I changed the fluid. So I assume that it is coming from the hyd case.

When I shut off the engine I could hear the fluid pushing past the Oring seal I put on the shifter and when I pulled the hyd dipstick there was a whoosh sound and the seal stopped leaking.

I unscrewed the trans level plug and a quart drained out the hole. The hyd dipstick shows only half full since I topped it off a last month.

I looked into the fill hole on the hyd top plate that was installed when the backhoe was put on and 3-point levers removed. I could see the PTO and nothing else. Does the stock hyd top plate have a vent on it? The replacement plate does not have a vent.

Since there is no hyd pump or pipes anymore, could the churning PTO alone cause a pressure differential between the hyd case and trans case?

Is the fluid level in the hyd case much higher than the trans so the fluid leaks by gravity from the seal between the two? My thought is once the hyd level drops below the seal it will quit tranferring fluid. Is there a danger to run the hyd case too low of fluid even when the 3-point gears and levers are removed?

Sorry for all the questions at once, but I must include all pertinent details.
o
 

[Dean]

The hydraulic lift cover needs no vent as there are several passages through which pressure can equalize. Perhaps you can simply leave the fill plug a bit loose?

If there is no vent in your blank cover, you need to create one to allow pressures to equalize.

Yes, oil can/will migrate from sump to sump past worn seals by gravity.

Dean
 

[Oaf]

Thanks much, Dean. I"ll try a loose plug and see if that takes care of my leak issue. If so, I can easily make a vent.

Is the PTO in the hyd case supposed to be bathed in oil at all times? Because the fluid level in the hyd case is getting pretty low.
o
 

[Dean]

Tractors with hydraulic systems have a hydraulic dipstick near the PTO engagement lever. I'm not sure if your tractor will have this dipstick or even provisions for one.

If you use the same NH 134D spec oil in all three sumps as is currently recommended, simply keep the sumps filled to the same level to prevent migration from sump to sump.

Dean
 

[Oaf]

There is a hyd dipstick, but I don"t know whether the fluid fill level in each of the three cases of the 600 series is the same. I use the 134D in all three as recommended on this board, and after this episode I"m sure glad I did!

I"ll vent the hyd case and let you all know if that cures the shifter leak.

Thanks again!
 

[gatchelguy]

I think the dipstock seals itself. Just leave it loose. Don't insert it all the way. And if I recall, there is a lip seal in the shift cover around the shaft.
 

[Oaf]

Yes gguy, there are two Orings on the dipstick shaft. Instead of running loose, I drilled a small hole in the 1/2-in socket slot of the top fill plug and that did the trick. I filled the plug inset with loose steel wool to keep the dirt out but still allow pressure equalization.

After running it there was no real fluid exchange and the seal didn"t leak at all.

SUCCESS!!!!! Thanks everybody for your suggestions.