4720 Power Steering Intermittently Locks Up

[ROBERT70]

It's a 2007. Open station. It only has about 300 hours on it. 'Course, that means it is long out of warranty.

In retrospect, this problems seems to occur when doing lots of lock to lock steering wheel maneuvering while using the FEL. Note however that the bucket is generally empty and I'm not calling for any other hydraulic functions at the same time (i.e. not raising/lowering/dumping/curling the FEL or raising/lowering the 3PH rear blade nor performing any hydraulic angling/offsetting/tilting of the blade). 4WD is generally engaged when this happens. I generally see the problem in colder weather plowing snow, but just recently saw it in normal spring temperatures as well.

I have had 2 of the 4720's and both have had this problem and still do. You can spin the steering wheel in circles when it happens with no motion at the wheels. Has anyone figured this out yet? JD dealer is no help! The problem is so intermittent that the dealer wanted me to come get it. I had to go there and play with it for hours and I got it to fail. Dealer replaced the pump and sent me on my way. One week later I'm back to the same issue it failed again. Dealer said we have no idea and washed their hands of it. This tractor is a 2010 and I have just been living with it. Please help if you can. Thank's everyone! Robert
Notes; Happens in any season any temp.
" in or out of 4x4
" with a load or empty bucket
" when ever it feels the need to upset me!!!

 

[texasranger556]

I have had 2 of the 4720's and both have had this problem and still do. You can spin the steering wheel in circles when it happens with no motion at the wheels. Has anyone figured this out yet? JD dealer is no help! The problem is so intermittent that the dealer wanted me to come get it. I had to go there and play with it for hours and I got it to fail. Dealer replaced the pump and sent me on my way. One week later I'm back to the same issue it failed again. Dealer said we have no idea and washed their hands of it. This tractor is a 2010 and I have just been living with it. Please help if you can. Thank's everyone! Robert
Notes; Happens in any season any temp.
" in or out of 4x4
" with a load or empty bucket
" when ever it feels the need to upset me!!!

You mention being able to turn the wheel in circles. Is there more or less resistance than normal in the steering wheel when it happens? The OP sounds like the steering wheel gets much harder to turn.


Also, are your tractors hydrostatic transmission?

 

[beenthere]

Puzzling situation.. but I'd be looking for places to hang a hyd. pressure gauge to see if there is a pressure spike or drop.

Have no clue without more information.

 

[ROBERT70]

You mention being able to turn the wheel in circles. Is there more or less resistance than normal in the steering wheel when it happens? The OP sounds like the steering wheel gets much harder to turn.


Also, are your tractors hydrostatic transmission?

They are hydrostatic transmission. resistance feels the same as if the wheels were moving/steering.

 

[gbw]

My 4320 did something like that, it was the rubber boot under the steering wheel seizing steering shaft - evidently a bushing at the top of the boot wore out.

 

[mike48130]

I would like at your tilt steering. It could be that knuckle in there binding. Next time try moving rhe tilt.

A good piece of information would be howbeit feels when it doesn't turn. Is it a hard mechanical lock or feels lime it is winding up like a spring. The first is in the column the second is in the hydraulics.

 

[texasranger556]

Robert said his steering wheel doesn't feel any different when the tires stop turning.

I don't have a service manual for a 20 series but I'd guess it is plumbed similar to my 4400 HST which uses the front gear pump to supply the steering which has a 1500 psi relief, then through the oil cooler which has a bypass valve set to 60-100 PSI, or filter with internal 10-30 psi bypass, then charge circuit in the HST. The charge relief valve is 100-150 PSI.

OP mentioned the problem happens more often when doing a lot of lock-to-lock steering which means the relief is being exercised more often. I wonder if it's getting stuck. I don't know where it is physically located though and how hard it would be to remove and inspect. The manual doesn't really talk about it other than in the schematic.

 

[mike48130]

Robert said his steering wheel doesn't feel any different when the tires stop turning.

I don't have a service manual for a 20 series but I'd guess it is plumbed similar to my 4400 HST which uses the front gear pump to supply the steering which has a 1500 psi relief, then through the oil cooler which has a bypass valve set to 60-100 PSI, or filter with internal 10-30 psi bypass, then charge circuit in the HST. The charge relief valve is 100-150 PSI.

OP mentioned the problem happens more often when doing a lot of lock-to-lock steering which means the relief is being exercised more often. I wonder if it's getting stuck. I don't know where it is physically located though and how hard it would be to remove and inspect. The manual doesn't really talk about it other than in the schematic.

He said in the first post the steering wheel freezes. The normal feeling statement was made in reference to loaded or unloaded bucket normal use.

 

[texasranger556]

He said in the first post the steering wheel freezes. The normal feeling statement was made in reference to loaded or unloaded bucket normal use.

I was referring to Robert who posted yesterday. The OP hasn't posted in 4 years.

 

[mike48130]

I was referring to Robert who posted yesterday. The OP hasn't posted in 4 years.

Ah. My bad. Doesn't the front pump feed the hydro and steering and on the 4x10 series the pto and 4x4. I would check the steering psi. It has its own pressure relief. Could be sticking I would guess. I would pull it and clean it then test the pressure.