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548E John Deere skidder

Started by Hogdaddy, July 14, 2020, 11:08:47 PM

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Hogdaddy

Just getting back into logging after several years out... bought a 548E... seems like a good skidder as I have run it for about week now pretty good, but 2 questions... You can hear the hydraulic pump running, not really any strange noises, just a hum like I guess, when you move the grapple though, not as noticeable. It does, every now and then, get a little stiff driving, but don't last over a couple of seconds at a time. The hydraulic fluid is at the right level.  Anything to worry about?

The other noise is a ringing like sound that has to do with the transmission.. not real loud, but noticeable when at low RPMs. the noise stops when you put it in park. Fliud is slightly to full right now.  

Any idea or experieces that you guys have had with those items?
If you gonna be a bear, be a Grizzly!

mike_belben

Start by checking for sump strainers that may be restricted and causing pump cavitation in each system.  Svc manual should call them out.  

Does everything appear to work at full strength so to speak?
Praise The Lord

Hogdaddy

Yeah, I don't see anything wrong with the transmission... the grapple seems a little weak when lifting, but I'm not for sure because I've never been around any other grapple skidder. Like it seems to strain it some to pick up a tree with 500 ft in it. It will pick it up, but you can't just grab it and go.  Single arch.  Is that normal?
If you gonna be a bear, be a Grizzly!

mike_belben

That i dont know.  Im a mechanic who only pretends to log from time to time. Never run a skidder.
Praise The Lord

Autocar

I would think a 500 bd.ft. log you should be able to run away with it .
Bill

Hogdaddy

Yeah, that's what i was thinking Autocar. As far as pulling, no problem, but the grapple is slow to lift the log



\
If you gonna be a bear, be a Grizzly!

mike_belben

Find you a honkin stick of timber and have someone grapple it up and down over and over while you use a mechanic stethoscope or long screwdriver or prybar with your ear against the handle to listen all over your hydraulic system.  The loudest site houses the issue.  It could be cavitation from a clogged sump screen, leakage around the pump gears or vanes, a leaky or pitted relief valve or a cracked spool bank.  I guess a really worn spool could do it too but probably rare if you dont have 30k hours on it.
Praise The Lord

moodnacreek


kiko

If the pump loads when no functions are being used and releases as the boom , for example, is moving then that means that there is a leak in the close center system.  It could be the main relief at the control valve. If so you can usually hear it hissing at control valve when the hydraulics are in neutral.  The pressure leaves the pump and goes into the steering priority valve. If you are loosing steer pressure occasionally the leak could be in that valve.  The hydraulic tank on that machine originally had a mesh screen where the suction hose comes out, it can come out and pieces will get lodged in the priority valve and control valve main relief and damage the pump as well.  A bad pump can also cause this issue.

mike_belben

Praise The Lord

longtime lurker

Quote from: mike_belben on July 15, 2020, 08:34:05 PM
Quote from: moodnacreek on July 15, 2020, 06:59:09 PM
A listening stick.
Doesnt seem to work on my kids.
Swing it harder: I seem to recall that worked on me.
The quickest way to make a million dollars with a sawmill is to start with two million.

moodnacreek

It taught me not to get caught.
















Hogdaddy

Well, chechecked the pressure today, 2600 when starting to pick up the grapple, but dropped quickly to 1900 while still holding it up.. guess i need a new pump.... ::)
If you gonna be a bear, be a Grizzly!

mike_belben

Open center hyd?  Please open up the pump to verify wear before you send it off.  It may still be a relief valve.  Id try shimming the relief spring and if needed, lapping the poppet valve then retesting first.  If pressure doesnt increase with more spring behind the poppet then yes the pump is suspect.  But a cracked spool block or sectional O ring could do it too.  

The hottest spot in the system as checked with an IR gun is likely where the bypass is occuring.  Fluid that does no work dissipates its potential energy via heat. 
Praise The Lord

Hogdaddy

It's a closed centered system, but very well could be bypassing somewhere other than the pump. Just talked to my mechanic, he said I need to be sure it wasn't bypassing anywhere.
If you gonna be a bear, be a Grizzly!

mike_belben

If you cant find a relief or sectional leakage issue, i think id pull the grapple cylinders and repack them as the first stage of throwin parts at it.  Its about the cheapest thing you can do and never a waste.

   I think bypassing around the piston face could give the results youre experiencing.  
Praise The Lord

kiko

The pump pressure should be 3000psi with the hydraulics in neutral, as you  raise the boom that pressure should drop to what ever pressure is necessary to move the boom with its current load.  When a function is bottomed out and still activated the pressure should return to 3000.  The 3000 is achieved on the pressure adjustment the pump. The main releif in the inlet section  is set higher than the pump adjustment  . Under the majority of operations the main relief does not even come it to play. 

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