4640 tractor

[jenkinsph]

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.

 

[Kyle_in_Tex]

Does the reservoir, up by the fuel tank run dry when you run out of hydraulic? That would be a mark in favor of a weak trans. pump or a high volume leak downstream. Does this unit have a high/low on the trans?

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]

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?

 

[Rwelder]

Powershift

 

[Tx Jim]

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.

 

[Rwelder]

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]

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

If hyd filters plugged that quickly then I'd be suspecting brake linings deteriorating causing the hyd problems.

 

[Rwelder]

Thanks for info that's what we were going to check next.I will let you know how it comes out thanks again

 

[mollyatbrowntown]

I need to drain my fuel tank on my 4640 John Deere Tractor. I cannot find the drain plug. Where is it located.

 

[beenthere]

:welcome" to TBN

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.