M4-071 Shuttle Shift Issues (Won't Drive Forward)

[dajwilso85]

Problem Description
I have a 2019 M4-071 with about 220 hours on it. I was brush hogging recently and things were going well. Later on that day after I was done, it started having a problem where it would not move forward when shuttled to F and when its shuttle to N it tries to go in reverse. R is still reverse.

Sometimes the tractor will move normally, but usually not.

So the behavior is like this given the tractor is in gear, parking brake is off and foot taken off clutch:

• I shuttle to F, the tractor does not move forward.
• I shuttle to N, the tractor starts moving in reverse.
• I shuttle to R, the tractor starts moving in reverse.

This happened after I was brush hogging for a couple of hours. Another thing that happened was that it was hard to start - it would turn over but make a choking / grinding / squeel noise (hard to describe) and not actually start up. Once it cooled down some more it started OK and has since then. This all happened the same day.

Has anyone else seen anything like this?

Troubleshooting

I'm no tractor tech, but I've tried to do some troubleshooting after I got the shop manual.

The dash panel where it shows F/N/R shows the correct position, and it does complain with the warning beep if you try and put it into F or R with the parking brake on.

I found in the shop manual about testing the voltage at the shuttle sensor wiring (shuttle sensor shown in shuttle_sensor.png) harness and it appeared to be correct (5 volts).

I found in the shop manual information to get the tractor into TST-1 mode where you can observe various readings and check error codes (tst1_sensor_info.jpg screenshot) and observed the values under certain conditions:

T12 and T13 are at about 2.2 and 2.74 volts when the shuttle is in neutral (respectively).
T12 and T13 are at about 0.62 and 4.3 volts when the shuttle is in forward (respectively).
T12 and T13 are at about 3.81 and 1.13 volts when the shuttle is in reverse (respectively).

Those seemed to be in range based on what I think I read in the manual.

Since it does move smoothly sometimes, I suspected something electronic. I replaced the shuttle sensor located under the shuttle lever (shuttle_sensor.png screenshot) but it did not fix the problem.

The manual says the ECU takes the signals from that sensor and the shuttle switch (which appears to just detect if you're in neutral) and activates the F or R solenoids, so I guess those are just getting a bad signal somehow.

I see a page about testing the shuttle solenoid valve wiring harness, so will give that a shot next (shuttle_solenoid_valve.jpg screenshot).

 

[dajwilso85]

Problem Description
I have a 2020 M4-071 with about 220 hours on it. I was brush hogging recently and things were going well. Later on that day after I was done, it started having a problem where it would not move forward when shuttled to F and when its shuttle to N it tries to go in reverse. R is still reverse.

Sometimes the tractor will move normally, but usually not.

So the behavior is like this given the tractor is in gear, parking brake is off and foot taken off clutch:

• I shuttle to F, the tractor does not move forward.
• I shuttle to N, the tractor starts moving in reverse.
• I shuttle to R, the tractor starts moving in reverse.

This happened after I was brush hogging for a couple of hours. Another thing that happened was that it was hard to start - it would turn over but make a choking / grinding / squeel noise (hard to describe) and not actually start up. Once it cooled down some more it started OK and has since then. This all happened the same day.

Has anyone else seen anything like this?

Troubleshooting

I'm no tractor tech, but I've tried to do some troubleshooting after I got the shop manual.

The dash panel where it shows F/N/R shows the correct position, and it does complain with the warning beep if you try and put it into F or R with the parking brake on.

I found in the shop manual about testing the voltage at the shuttle sensor wiring (shuttle sensor shown in shuttle_sensor.png) harness and it appeared to be correct (5 volts).

I found in the shop manual information to get the tractor into TST-1 mode where you can observe various readings and check error codes (tst1_sensor_info.jpg screenshot) and observed the values under certain conditions:

T12 and T13 are at about 2.2 and 2.74 volts when the shuttle is in neutral (respectively).
T12 and T13 are at about 0.62 and 4.3 volts when the shuttle is in forward (respectively).
T12 and T13 are at about 3.81 and 1.13 volts when the shuttle is in reverse (respectively).

Those seemed to be in range based on what I think I read in the manual.

Since it does move smoothly sometimes, I suspected something electronic. I replaced the shuttle sensor located under the shuttle lever (shuttle_sensor.png screenshot) but it did not fix the problem.

The manual says the ECU takes the signals from that sensor and the shuttle switch (which appears to just detect if you're in neutral) and activates the F or R solenoids, so I guess those are just getting a bad signal somehow.

I see a page about testing the shuttle solenoid valve wiring harness, so will give that a shot next (shuttle_solenoid_valve.jpg screenshot).

When I checked the shuttle solenoid valve wiring harness voltage (shown in the shuttle_solenoid_valve.jpg screenshot), I turned the main switch on and moved the shuttle to F and then checked voltage, then to N and checked voltage, then to R and checked voltage - both the wires always had batter voltage (12.5 volts) all the time which seems strange as it says one wire is for F and one is for R, so I figured in N they would both have nothing and in F one would be hot and the other one nothing, etc but they were always 12.5 volts all the time.

One other thing that seems odd, when I left the connector unplugged and started the tractor up I assumed that no matter which way I had the shuttle (F, N, R) it would go no where since no signal was being sent but it actually tried to go in reverse in all positions this way.

 

[McMXi]

This might be utterly irrelevant, but a few months ago the shuttle shift lever in my M6060 felt odd. I wasn't experiencing any issues related to getting into F/N/R, but I removed the plastic cover from the steering column and noticed that the two bolts (see orange arrows) were loose. I removed them, applied blue Loctite and reinstalled them.

It can be tempting to jump into the deep end of a problem only to find that the solution is at the shallow end. Since this is shuttle related, it might be worth checking that the shuttle lever is working as it should. I would expect the M4 to have a similar system to the M6060/M7060.

Good luck with your trouble-shooting and no doubt others will be along to offer some good ideas of where to look, and what to look for. @whitetiger and @North Idaho Wolfman usually help most figure it out and fix the problem.

 

[dajwilso85]

@McMXi thanks for the comment! That was actually my first thought - start with the shuttle shift lever and work from there. My M4-071 has a sensor there instead of linkage though - and so I replaced that sensor first (screenshot here with the sensor circled) but it is acting exactly the same way afterwards:

 

[dajwilso85]

Another odd symptom - if I have the tractor in gear, put the shuttle into F position and let out on the clutch it does not move as noted above (that is the original issue I noticed) but on top of that if you are sitting there like that and you press the de-clutch button on the shifter it will also start moving in reverse. So that's shuttle lever in F, foot off the clutch, tractor in gear, then press the de-clutch button it moves in reverse.

 

[McMXi]

@McMXi thanks for the comment! That was actually my first thought - start with the shuttle shift lever and work from there. My M4-071 has a sensor there instead of linkage though - and so I replaced that sensor first (screenshot here with the sensor circled) but it is acting exactly the same way afterwards:

Reading your first post more carefully I see that you mentioned the shuttle sensor. You seem to have a good approach for troubleshooting the issue, and the WSM should/might help. Looking forward to hearing all about the resolution.