I have a 4640 john Deere tractor and after running for about an hour all the hydralics shut down, I changed out all filters and cleaned the screen in bottom of trans. The screen was almost stopped up but clean now, still does same thing when hot after it cools down it starts moving again could it be in main pump or trans pump has anybody ran into this problem before?
4640 tractor
- Thread starter Rwelder
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Zebrafive
Super Member
I'd lean towards the main pump. Something getting hot and sticking maybe?
Trans pump is a pretty simple gear pump.
It may take more than one filter cange, and screen cleaning to clear things up?
How old is the fluid? Correct level?
Trans pump is a pretty simple gear pump.
It may take more than one filter cange, and screen cleaning to clear things up?
How old is the fluid? Correct level?
Zebrafive
Super Member
Tran pump is so named because it is in the trans. The trans is the reservior and it pumps to the main pump suction side. Main pump feeds all hydraulics, steering, 3pt (rockshaft), and SCVs
jenkinsph
Super Star Member
It would be good to know how hot the hydraulic oil is when you are having this problem. The reservoir capacity is small considering the flow rate capacity. You may have cooling issues or excessive wear on the pump but there are a few things to consider before pulling the pump. I think that it isn't as likely to be a restriction in the lines or filters as you say it works fine when cool.
The transmission pump (gear type) is pumping IIRC whenever the engine is running and the clutch is engaged. Don't know how it bypasses when the main pump is out of stroke (no hydraulic functions being operated) and full pressure is reached. Will have to check the drawings to see.
If it is similar to the 4020 the priority valve shifts at pressures below 1900 psi to steering and brakes only, so does the rockshaft work at startup then it fails shortly before the steering fails?
Do you have a pressure guage to check the system pressures cold and hot?
I would also add there is a filter above the drain plug on the bottom of the pump that is about the size of a shotgun shell that I had fail on my 4020, for a 4640 this is part # R27173 on the stroke control assembly. This is easy to check and get to from the bottom of the tractor, remove the drain plug assembly which has a small rod with this filter on it. This small filter screen if plugged up will shut down the pump. If you look at the stroke control in Deere parts it is marked as #17.
The transmission pump (gear type) is pumping IIRC whenever the engine is running and the clutch is engaged. Don't know how it bypasses when the main pump is out of stroke (no hydraulic functions being operated) and full pressure is reached. Will have to check the drawings to see.
If it is similar to the 4020 the priority valve shifts at pressures below 1900 psi to steering and brakes only, so does the rockshaft work at startup then it fails shortly before the steering fails?
Do you have a pressure guage to check the system pressures cold and hot?
I would also add there is a filter above the drain plug on the bottom of the pump that is about the size of a shotgun shell that I had fail on my 4020, for a 4640 this is part # R27173 on the stroke control assembly. This is easy to check and get to from the bottom of the tractor, remove the drain plug assembly which has a small rod with this filter on it. This small filter screen if plugged up will shut down the pump. If you look at the stroke control in Deere parts it is marked as #17.
Last edited:
jenkinsph
Super Star Member
When you say after it cools it will start moving again are you referring to the drive train?
jenkinsph
Super Star Member
The reason I asked about the drive train specifically is because the transmission pump as I understand it provides the oil for the transmission at low pressure and also provides a low pressure charge supply to the main pump on the front crankshaft.
Two scenarios,
If the rockshaft, steering and remotes ports stop working and the transmisssion continues to shift then it is likely to be the main pump.
If everything fails including transmission shifting then it is likely to be the transmission pump.
The transmission pump is the cheaper of the two by far.
You can rebuild a worn mainpump with a kit from Deere
If you have a way to lift the rear cover and seat off the tractor changing the hydraulic pump is fairly simple. Likewise removing the main pump is easy enough and the way the piston assemblies are assembled from the outside similar to a radial engine makes it easier to rebuild too.
Before disassembling the above I would first remove the stroke control assembly from the bottom of the hydraulic pump as I mentioned in the earlier post. This is a quick job with the right sockets and will allow you to check the filter screen on the pump.
I bought a very nice 4020 in 1978 which the new dealer's mechanic failed to fix for $4200 after a few days of searching and diagnosis I found the screen on the stroke control to be the problem. At that time it was a $15 fix, I was happy but the dealer/owner wasn't.
Two scenarios,
If the rockshaft, steering and remotes ports stop working and the transmisssion continues to shift then it is likely to be the main pump.
If everything fails including transmission shifting then it is likely to be the transmission pump.
The transmission pump is the cheaper of the two by far.
You can rebuild a worn mainpump with a kit from Deere
If you have a way to lift the rear cover and seat off the tractor changing the hydraulic pump is fairly simple. Likewise removing the main pump is easy enough and the way the piston assemblies are assembled from the outside similar to a radial engine makes it easier to rebuild too.
Before disassembling the above I would first remove the stroke control assembly from the bottom of the hydraulic pump as I mentioned in the earlier post. This is a quick job with the right sockets and will allow you to check the filter screen on the pump.
I bought a very nice 4020 in 1978 which the new dealer's mechanic failed to fix for $4200 after a few days of searching and diagnosis I found the screen on the stroke control to be the problem. At that time it was a $15 fix, I was happy but the dealer/owner wasn't.
Kyle_in_Tex
Super Star Member
Your problems sound exactly like the lower pump is leaking/bad. Unfortunately, you'll need to split the tractor to fix it. This happens on high time machines sometimes. It would be wise to put in a new clutch, resurface the flywheel pressure plate, new seals everywhere you can get to and such. You'll be good to go for a long, long time after this.
Tx Jim
New Member
What kind of debris was stopping up sump screen. If it was a fibrous substance it's possible brake linings are failing. Loss of hyd's on closed-center hyd's such as on your 4640 are normally caused by either a low or high pressure leak. Does hyd oil get hot? If so this indicates a high pressure leak. What type of trans PS or quad?
Tx Jim
New Member
I would recommend testing pressures of trans pump and main hyd pump before replacing any parts. Since it's a PS you must be losing trans pressure for it to stop moving. Losing trans pressure also means you will lose 3pt,scvs and then steering & brakes. Have you tried it to see if it will stop moving in all the 8 FWD and 4 rev gears? A PS is a little harder to diagnose than a quad because so many more hyd ports require testing. IIRC trans pump psi should be 165-170.
I'm just now getting back to tractor and found filters dirty again changed filters and new fluid and also cleaned filter in main pump and so far it's working great I appriciate the info hope all is having a good 2011 thanks again
Tx Jim
New Member
If hyd filters plugged that quickly then I'd be suspecting brake linings deteriorating causing the hyd problems.
mollyatbrowntown
New member
I need to drain my fuel tank on my 4640 John Deere Tractor. I cannot find the drain plug. Where is it located.
beenthere
Super Star Member
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Looking at jdparts.com (registration is free), and putting model 4640 in, then under alphabetic listing going to "Fuel Tank", this pic shows a drain valve on the right side bottom, near the fuel shut-off. Says it is field installed (not sure if that means it doesn't come from factory with the drain).
Part item #19 in pic.
Looking at jdparts.com (registration is free), and putting model 4640 in, then under alphabetic listing going to "Fuel Tank", this pic shows a drain valve on the right side bottom, near the fuel shut-off. Says it is field installed (not sure if that means it doesn't come from factory with the drain).
Part item #19 in pic.
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