John Deere 440 skidder front and back diff full of hydraulic oil

[Frozendozer]

I pulled the plates off my old john deere 440 and started my spring time prep for a busy season of firewood cutting.  I wanted to make sure my front an rear diff levels were adequate so I removed the plugs that are on the side of the casing and in both instances a large amount of hydraulic fluid came out.  I didn't have a pan handy as I was expecting that fluid would require to be added.  upon viewing of my repair manual I observed that there is also a plug on the top of each casing were I suppose fluid was added, by the owner previous to me.  Is this the normal , that the fluid be in excess of the plug level of the side of the diff housings?  Perhaps fluid is being added via the diff lock system?  Learning lots of this beast and at this time kinda scared to continue without some advice 

[snowstorm]

yes the diff lock will keep the front full

[Frozendozer]

should I be draining some of it, at least to the level of the plug that is on the side of the diff housing?

[barbender]

Drain and replace with fresh gear oil, and figure out the source of the hydraulic oil. The differentials on the Ponsse machines are notorious for getting filled with hydraulic oil from the internal brake cans.

[Frozendozer]

my manual calls for John Deere hy-guard hydraulic oil   34 liters worth in the diff .   that's like almost 2 buckets worth....wow 

[barbender]

Ok, I misunderstood- the diffs call for hydraulic instead of gear oil?

[Brian w]

I'm not sure what year or model 440 you are referring to but John Deere differs from other equipment most models everything runs off of the hydraulics from the transmission it pumps fluid through  both differentials and the winch to keep them full by doing so as long as you keep the transmission full it in turn fills everything else. I recently learned about this the hard way. I payed thousands of dollars to get the transmission rebuilt because it was full of metal shavings and would lose hydraulic pressure. After I got the skidder back had the same problem and again transmission was full of metal so sent it back to the garage to find out the problem and the metal was coming from the rear differential.

[Grandpa]

Yes, Hy-tran in the diffs. Diff lock keeps the front full, and it has a return line to the transmission. In other words, don't worry about it. Rear should be filled to the plug on the side. If it is overfull, either someone overfilled it or it has a lot of condensation.

[Grandpa]

Brian w, I think Frozendozer's machine is a lot older than that. Winch and rear differential have their own oil.

I could be wrong but I thought it was a plain or an A.

Can you clear this up Frozendozer, those letters are important. (Or no letter).

[Frozendozer]

Grampa had is right, it's an older plain Jane 440.  I am told it's a 1966 vintage .   should I pull the drain plug on the rear diff to see if there is water in there?  

[Grandpa]

That's what I would do, but I usually do things wrong/the most difficult way possible.

[sidehill6]

frozen, I think your diff lock when engaged puts hydraulic pressure against a piston in the front diff which engages a clutch pack  giving you a locked differential, I think the only way it would fill the differential is if the piston and packings were leaking. when you disengage the lock springs relieve the pressure on the clutch pack giving you an open diff.

[Frozendozer]

sidehill 6 - I was thinking the same thing, that the differential lock is bleeding into the front diff.  I would think that perhaps in time it could build pressure and blow thru some seals elsewhere.   The rear diff I believe may also have a diff lock, judging from how it reacts when I kick the selector lever, perhaps that as well it leaking.  Perhaps I should drain both diffs to the plugs on the side of the casing?   

Grandpa , I seem to only learn the same way, but I am trying not to, with this machine. It's nice to have z site like this to discuss my next moves before I feel the effects of the Bozo factor 

[Frozendozer]

sidehill6   after some thought and looking at my repair manual, I don't have an operator's manual, perhaps by filling the diff with oil it's possible that the front diff lock might not engage properly.   I applied diff lock and pushed on a big rock and only one tire would spin .   I am going to drain some fluid tomorrow and see if there is an improvement.

[Grandpa]

The front should be completely full, any excess oil returns to the transmission via the return line. 
The diff lock not working is common. It could be anything but the most common problem is the valve needs to be shimmed. 
The back axle should be locked all the time.

[teakwood]

Yes, Hy-tran in the diffs. Diff lock keeps the front full, and it has a return line to the transmission. In other words, don't worry about it. Rear should be filled to the plug on the side. If it is overfull, either someone overfilled it or it has a lot of condensation.

Or the rear brake is leaking and filling the diff.
I have a 540A, 1971.  I don't know how similar they are, front diff has to be full, because diff lock HAS to drain the used oil into the diff, there is a low pressure (like 1/2" or 3/4" hyd return line back to the trans), so front is full and rear is half full (one bucket of oil) till the level plug. 

[Grandpa]

Brakes should be in the transmission on this one.

[Frozendozer]

I haven't gotten out to my machine yet, but revising the manual I have indicate that the brake is not in the tear dif. Additional the repair manual show that the rear diff also has a diff lock in it.   tomorrow I am gonna go and have z look.  Stay tuned folks 

[snowstorm]

the rear is locked and can not be unlocked on a 440  a  b