John Deere 401 with reverser, What did I do?

JD401
Was loading up a semi with bales yesterday when the hydraulics started feeling a little weak.
Had a few hours to kill before the next load so I figured being that I had a spare transmission filter on the shelf I would put in in while I had the time.
Dropped the canister and discovered the filter I had on hand was the wrong one.
No big deal, I rinsed the old filter out in some solvent, blew it out and put it back in.

Now the fun began.
Hydraulics for loader, steering, 3 point etc were working fine but no forward or reverse movement.

First thought was that something was buggered up in the relief valve.
Pulled it out and checked it over and all as well, installed it, filled system back up with no difference.

Next thought was the transmission pump must be weak and not able to prime itself.

Checked for pressure at the reverser test port and had nothing.
Hung a vacuum pump off the reverser test port and pumped on it until it drew a 1/4 cup of oil threw it.

Still no forward or reverse movement but it was starting to make the lug down noise when pushing and releasing the clutch pedal.

Shy of splitting it to check the transmission pump any suggestions?

I was thinking of hooking a line off one of the remotes to back feed fluid through the filter/pump/pick up tube to prime the system.
Anybody had any experience or success with a weak transmission pump?

If frt end loader & power steering are operating then trans pump must be operating because trans supplies oil to frt pump. I suggest you check reverser control linkage. Reverser control linkage on JD tractors of that era have a long history of pin failure that secures shift linkage arm on reverser control valve.

(quoted from post at 05:52:43 05/06/23)
If frt end loader & power steering are operating then trans pump must be operating because trans supplies oil to frt pump. I suggest you check reverser control linkage. Reverser control linkage on JD tractors of that era have a long history of pin failure that secures shift linkage arm on reverser control valve.

Click to expand...

Thanks for the insight TX Jim I needed the reminder that the front hydraulic pump relies on the transmission pump to feed it.

Messed around with it for half the day today.

-Checked the roll pin on the clutch control rod to reverser and all was good.
-Pulled the transmission filter relief valve, tore it down to nothing, checked, cleaned and reinstalled it with no change.
-Advanced and retarted the reverser control rod from one extreme to the other with no improvement.
-Though I have one I have not yet put a pressure gauge on the reverser test port because right now with the plug out it has zero flow let alone pressure.
-Pulled and checked the spring and shims from the pressure control on the bottom of the reverser and all seemed good, no change.
-Loader, steering and 3 point still working fine so I am assuming steering priority valve is happy and is only for high pressure control.
-Cooler bypass valve in my understanding should not effect operation so I have not dug into that.
-Best as I can tell is with zero pressure going to reverser assembly there is no reverser clutch engagement happening.
Without touching the clutch pedal I can shift through all the gears and shift high to low with engine running as well engage or disengage pto control with out any meshing or grinding sounds.

Unless you have any better suggestions my next step will be to remove the reverser and brake valve, fire it up and see if it has any flow from the clutch casting to the reverser assembly.

This post was edited by Determined on 05/06/2023 at 05:17 pm.

I'm out of ideas but I'll keep thinking about your tractors reverser problems

I've seen this on Deere backhoes, which is the same basic driveline.... The clutch splines on the trans. input shaft are worn and
stripped out the internal splines of the clutch disk. If you don't drive the reverser, the reverser doesn't make pressure to drive the
wheels or feed pressure oil to the hydraulic pump. If you need to split the tractor, I've got a short cut to replace that input shaft,
otherwise you will have to remove the reverser from the tractor. Post again if you need assistance with that input shaft replacement.

Played with it again yesterday, can't really say that I found anything plugged, broken, out of adjustment or out of place. Need to go to town today so I will pick up a new set of filters for it, don't really think they will improve the situation but the oil is drained right now so it will be an easy change.

What did I do yesterday?
-Pulled front cover off of reverser.
-Removed and inspected pressure control valve and spring and shims.
-Removed and inspected clutch control valve.
-Double and triple checked linkage and travel on clutch control valve and forward/reverse valve.
-Pulled and checked strainer, next to nothing on it.
-Pulled transmission filter bypass valve again just to make sure it wasn't in backwards or something stupid like that, all was well.

Observations;
-Prior to removing reverser front cover I removed plug, shims and spring from pressure control valve and started the engine,
reached in and pushed on valve with a screwdriver and could feel definite firm pushback every time I would push the valve towards it's seat.

Unless it was a total fluke it would seem unlikely that something let go at the exact time I decided to drive into the shop to change a filter yet what could possibly have changed or let go during a simple filter R+R?

If for example the filter was plugged solid the bypass valve would open and the machine would still function.

If the transmission pump failed the filter housing would not be refilling itself after removal nor would the functions running off of the front pump be working properly. Currently the steering, loader and 3 point are all working.

As far as anything acting out of the ordinary prior to the failure when the filter was pulled;

-When real cold in the winter I would start the tractor and back it out of the shop to warm up, typically it would take 2-3 minutes before it would go forward, if warm out it would have forward right away.

-The reason I felt a filter change may help it was I could use it hard for say an hour without any problems then it would start to get a little sluggish when fully raising the loader to stack a top row on a semi, if I shut it down for 10 minutes it would work fine again.
In my thoughts this is not enough time for any amount of cooling to make a difference so my thinking was going towards crud accumulating on a filter or strainer settling back down when shut off.

Maybe totally unrelated but the last few bales I moved before driving to the shop it felt like there was more load than normal to overcome when moving the joystick to up, down tilt etc.

The lever was harder to move ? or the loader seemed to labor when raising the load ?

That filter relief valve you took out, did you take it all apart to see if the shims were flattened out ? Flattened shims will give the valve a bogus operation. Is the poppet valve inside the spool loose or possibly stuck . I've seen a chip of crap so small that held the poppet off it's seat, you'll wonder how that happened. Just grasping at straws without being there.

Good Morning Roy.

Regarding your first question, the joystick for control of the loader has always (25+years) been butter smooth on this machine and had the same feel when lifting the loader with an empty bucket or a full bucket.
The loader was not laboring once a function was selected, the best way I can describe it is;
Instead of smoothly pulling on the joystick with say 4-5 lbs of force to initiate lifting it was taking more like 8-9 lbs of pull followed by a clunk feeling as the spool overcame initial resistance after which the feel and operation was normal.

On your second question the transmission pump filter bypass valve just consists of a sleeve a spring a valve and two roll pins. It was completely disassembled cleaned and inspected. The spring measured within spec according to the factory manual.

I will put the new filters in today and see what it is doing but I have my doubts that anything I have checked, cleaned or adjusted so far is the source of the fault.

It's alive

Put the filters in, filled the oil and hung a gauge on the reverser.

Started it up and at first it was not reading any pressure.

Not a big surprise as the hydraulics were empty.

Gave it a minute then tried the steering wheel, steering good.
Tried the loader, working well and the high resistance was gone.

Tried the 3-point and it lifted like it should.

Looked down at the gauge and guess what 170 psi.

Got on tractor and put it in gear, at first a little sluggish but starting to move in reverse.
Operated the reverser back and forth a few times and now it's moving forward and back.

Backed out of the shop for a quick test and could tell right away the clutch control needed as adjustment as it was grinding when trying to shift ranges.

Set up the clutch control and went for another test.
Everything working as it should with the exception of the speed of engagement when either releasing the clutch pedal or changing from reverse to forward motion.

With tractor idling in park reverser pressure comes up instantly when moving reverser control from forward to reverse.
When control is moved from reverse to forward it seems to have a 1/2 to 1 second lag time before full pressure is reached on gauge.

Guess I will see how it is once fully warmed up but given that it was previously (many years) a little slow going into forward when cold I can live with that for now.

Thanks to everybody for the input.

About the only thing I can think of that even might have been the problem was the valve in the reverser pressure control, it had several light lengthwise scratches that I polished out when it was apart.