Deere 4400 low charge pressure, won't move

[dustin63933]

Hey all, I'm working on my john deere 4400 tractor 1700 hours and it wont move forward or reverse. After backing it off my trailer (as ive done 100x) it stopped moving after a soft 1foot drop. Before all of this it's been a very reliable tractor and 200~ hours ago I replaced the fluid and filter and cleaned the mesh screen. It's always had great pushing power and everything you could ask for. It only has 30psi of charge pressure at 2000rpms. Now some things I've done is.

Changed the filter, cleaned the mesh screen (which was pretty clean, no big chunks, mainly clutch material), taken the charge relief valve off and the poppet was smooth and nothing foreign was in the hole. I even checked with a boroscope & spring was tight. The actual ports for forward and reverse were 30psi also, instead of the 6000 the the service manual calls for. The FEL works great along with the rockshaft. The oil is not foaming like its sucking in air. I took off the bottom rubber hose and the plastic manifold by the hydraulic pump to check for blockages or air leaks.

The rear pump is building 2600psi (FEL, 3 point) and the front pump is building 1600psi (HST & PS)as the manual says it should. I took apart the steering control unit and everything was clean inside except for a little relief valve that was stuck in the closed position. There were small metal chunks attached to it, it was jammed in there, after cleaning and reassembling, the power steering works better than ever but no change to the charge pump pressure. I took off the rockshaft cover and examined all the gears and shafts and everything works and looks good. The gear shifter shifts in all gears and machine rolls in neutral with no weird noises. The HST pump is getting turned by the flywheel and the swash plate shaft is moving when I engage forward or reverse. The PTO spins and works just fine.

Now I know with 30psi the closed loop system of the HST its not gonna move and I can't find anything else to check. I've got the service manual and I've studied it quite a bit and searched the forums but I'm almost at a lost with what to try next. Is there some kind of inline filter from the oil cooler that I'm missing? Do I need to try to add a shim to the charge relief valve and see what happens? If anybody could point me in the right direction I'd sincerely appreciate it. I will reply back ASAP and send any picture or info you need. Thank you

 

[Williy]

Is the fluid up to par??
Do you have a parts list and diagram listing the parts?
With the diagram showing the parts and where they go
really helps to solve problems

willy

 

[ultrarunner]

Don’t know how much in common with the Deere 110 TLB?

When mine acted the same and the dealer started talking possible repair in the many thousands of dollars I got lucky doing research and found all my transmission woes were flywheel sensor.

The part now costs $100 to $150 from recent posts…

When mine failed the tractor just stopped moving with the pedals.

 

[dustin63933]

Is the fluid up to par??
Do you have a parts list and diagram listing the parts?
With the diagram showing the parts and where they go
really helps to solve problems

willy

Hey willy, Yes the fluid is up to par in the sight gage. Always has been never ran low and ive always used fluid from tractor supply that meets the j20 spec.

 

[dustin63933]

Don’t know how much in common with the Deere 110 TLB?

When mine acted the same and the dealer started talking possible repair in the many thousands of dollars I got lucky doing research and found all my transmission woes were flywheel sensor.

The part now costs $100 to $150 from recent posts…

When mine failed the tractor just stopped moving with the pedals.

Yeah I can't find a flywheel sensor or anything not even with a parts diagram and google. The tractor doesnt really have a lot of electrical stuff past the engine. It's really all mechanical back there.

 

[oldnslo]

Looking at the schematics you posted the charge relief would be the most likely culprit since they normally fail open but you have already checked that.

Does HST make any strange noises when trying to move.

Next check would be a flowmeter in the line from the cooler to the HST. This will tell you if you are getting charge flow to the transaxle HST. If getting flow then going to have to follow that flow path and see if there is an internal line that shook loose and oil is allowed to escape back into transaxle reservoir at low pressure.

Schematic shows simple mechanical control on the HST.. I.e. foot pedal directly operates the swash plate. is that correct?

 

[dustin63933]

Looking at the schematics you posted the charge relief would be the most likely culprit since they normally fail open but you have already checked that.

Does HST make any strange noises when trying to move.

Next check would be a flowmeter in the line from the cooler to the HST. This will tell you if you are getting charge flow to the transaxle HST. If getting flow then going to have to follow that flow path and see if there is an internal line that shook loose and oil is allowed to escape back into transaxle reservoir at low pressure.

Schematic shows simple mechanical control on the HST.. I.e. foot pedal directly operates the swash plate. is that correct?

Correct, the HST system is pretty mechanical with besides cruise control theres no electrical components to test. The only noise I hear when I press on the pedal is the engine changes tune just a slight bit, not much.

By internal line, you're saying on the inside of the HST itself, correct?
I wonder if I could tee off on the line from the cooler and check pressures there, would they be the 30psi im getting most likely or some other different pressure?

 

[dustin63933]

I may end up taking the front hydraulic pump apart and using a caliper and my eyeball for signs of wear. Maybe it's not getting enough flow, therefore no pressure? But power steering works great though so it seems unlikely.

 

[oldnslo]

If steering is working it is highly unlikely the pump is the problem.

Yes teeing into the line from the cooler should show similar 30 PSI.

Yes on suspecting a problem inside the transaxle HST assembly. If pure mechanical control the HST should try to move even with low charge. Would probably be noisy but still should try.

Will the tractor roll like in neutral or do you still have the HST braking effect?

 

[kennyd]

Don’t know how much in common with the Deere 110 TLB?

Very little.
The 110TLB was based on the 4610 series platform, much is different.