We have a John Deere 648E log skidder. It has a leaky wheel seal which has led to discussion about the axle over-filling if the brakes were leaking into the compartment. A local repairer who has experience with replacing wheel seals on this model has told the Boss that the transmission and axle oil levels are connected and controlled by the turbocharger boost pressure. Without a manual, and knowing that Mr Deere has in the past done some pretty crazy things, I am only 99% prepared to say this idea is a load of you-know-what. Has anyone heard of anything remotely like this ? Cheers. Maurie. Hervey Bay, Queensland. Australia.
Hmm, well I suppose they could pressurize the components to keep water out. We used to run a boost line to the hydraulic tank on 345 to help get oil to the pumps a little faster.
Back when I was in the navy we used to send green horns down the corpsman for 18" of sterile fallopian tube for the AC units.
Except in our friends case here,its true. the axles are pressurized by a line running from the intake manifold to the axles to return oil from the diff locks (which bleed into the axle) to the transmission.D,E, G and maybe H wheel loaders cant remember which ones) used the same principle.
Are you saying Deere uses boost pressure to push diff lock oil to the transmission or to pressurize the axle oil?
push oil back to trans. see pg 344 of this manual http://rockbreaker.com/images/file/Manuals/mobile/John-Deere-Axle-Service-Manual.pdf
Gentlemen, Thank you so much. I had a pretty torrid day replacing o-rings on the service-port relief valves of the machine in question and then had to replace a hose from the control valve to the articulation when it leaked. So I'm wearing clean clothes over a dirty etc . so I didn't look yet at your link thanks cutting edge. I do now understand what the boost pressure does. The machine will still have both wheel seals done next week. Cheers. M.
Well if you were to measure the air pressure local to you you would find it to be about 14.7 psi or 1 bar or some folks call it one atmosphere and others may use 76 mm of mercury. Now a turbocharger is a centrifugal air compressor driven from the waste gasses produced by the engine burning fuel. To extract more horse power from the said engine if you pressurise and cool the air and pump it into the cylinders (at a pressure higher than that of the atmosphere) it allows you to put in more fuel (air under pressure will contain more oxygen for a given volume than air at atmosphere pressure ) the more fuel you can burn the more power you recover. So to the axles well when you rev up the engine the air pressure in the intake manifold is increased to maybe 1-1.5 times natural air pressure, the pipe from the manifold then transfers this higher pressure to the axle casing also raising it to above the ambient air pressure thus preventing the water and other contaminants from getting in.
Hey Stock, Thanks for that Mate. But to save us both being embarrassed, I gotta point out that I wrote "do NOW" rather than "do NOT". But your brief explanation is excellent. I once had to rig my 12 litre Volvo truck to run for a couple of days without the turbo while I waited for a kit for it. She was one sick truck without boost! I have a gage on it. She gets up to 22 psi at the inlet manifold after the intercooler. Cheers. Maurie.
cutting edge, The down load you posted doesn't seem to have a page 344. I found reference to the system on page 05-120-10 or page 428. What seems to be implied by this page is that the seals in the differential lock are not adequate to hold all the oil being applied to the lock and that some of that oil will leak into the differential housing potentially causing an over full situation. There is reference to two tubes inside the differential connected to a separate sump outside of the axle housing where the pressure supplied by a source which could be boost pressure from the engine or regulated air from an air compressor which can vent to the separate sump. If the oil level in the differential is too high it will cover the ends of the tubes and the supplied air pressure will force the overage of oil through the tubes and into the separate sump. I saw no mention of using external air pressure to have anything to do with brake pressure but would agree that if the brake actuators were leaking they would cause an overfull situation in the axle and that oil would go to the sump. But if that were happening, the leaky wheel seals would only be the start of the repair as the axle would need to be removed from the machine to repair the root cause of the leak which would be the leaking brake piston seals. I guess I'm missing something here because the description of the system indicates that internal leakage of the brakes would cause oil of some kind, usually brake actuation oil is from the hydraulic system and differential lock oil might be from somewhere else, to go to some sort of sump and overfill it. Nothing in the description that I could find indicates that the axles operate with a positive pressure. It only indicates a positive pressure when the axle is overfull. The usual engineering practice for axles in machines that might occasionally work in water is to connect a hose in place of the vent, run the hose up higher in the machine and connect the vent to the higher end of the hose. Could you provide a better description of this system as I'm sure there is a hole in my understanding of how it could cause the wheel seals to leak.
Hey John, I did get page 344 but had to wait a while for it to download that far. Its actually pg 344 of the download, not the manual. The whole axle does have to come out of the machine to break it at the diff housing to get to the end of the half-shaft so you can remove it to get at the wheel seal. The wheel seals leak because they are worn, as the operators get these big skidders on some terrible angles that fully immerse the seals on one side in oil.
it is pg 344 of the PDF. Alas, the axle on this model wont over fill if the brake seals are leaking, but the tranny will. Once you see how the positive air works in this axle you will understand. I always thought it was a little wacky to share oil between the axles and tranny, but it works rather well.
Does your rearend have a breather on the top of the rearend?????? My trencher has close to the same rearend and maybe the same? It is a Deere (Funk)rearend used in the skidders.For the brake and the diff lock to work it gets oils from the hydraulic tank oil.It has a accumlater for part of the system.I know the accumlater has about 600lbs of nitrogen in it.Does you system have anything like that? Don't know anything about the boost pressure ,just stating how my machine works and is setup! I know this is a different setup then your talking oil isn't shared with the trans.The rearend this spring broke a tooth of the pinuion gear.When it did it cracked the cage where the brake and diff lock gets it oil from the hydraulic tank those filling the rearend with oil from the hydraulic tank.It was running out the breather on top of the rearend.As John stated(breather)could get to the line coming from the tank to plug,so lost a lot of the hydraulic tank oil. So the question does you machine have a breather on top of the rearend where it might be pluged and building up pressure and making the seals leak???????? Also does it have a accumlater some where? I know your talking a different set up,but i'm with John,but i don't know because my machine doesn't have the transmission connected to the rearend,and difentally doesn't use the turbo boost pressure thing!!!!! I guestion??? but don't know! Yes we had to remove the rearend also from the trencher to work on it the brakes(run in oil) and diff lock is internal with the planterys and short axiles internal also.I was thinking the rearend is actually make by Funk (which Deere owns know) Hydraulic and rearend oil is the same in my machine Deere hyguard.Good luck
Construct'O, That's why I asked the question to start with too. On the skidder, the two axles are driven by driveshafts from the trans. and are all seperate compartments. Who could ever follow the hoses on a John Deere machine to trace what goes where? And the only way to verify if there is a breather would be with the axle out of the machine but I would say "no" on our machine. With the system as described by our friends, if your diff-lock leaks, the axle oil level stays correct and so does the trans. because the diff-locks are activated by oil from the trans. If your brakes leak, the axle oil levels still stay correct because of the trick system as described, but the trans will overfill, because the brake oil comes from the hyd. tank. Yes there is an accumulator on the brake circuit. This all came up and got known around town when a skidder that always had high axle oil levels and the trans. was low got fixed with a new turbo! I was very sceptical when I got told about it, but now I believe it! Cheers. Maurie.