John Deere 6420S

[Einstien]

Friend of mine has a JD 6420S, its sat in my yard having had two mobile mechanics have a look - the second with laptop and JD software etc... neither can work out whats going on.

It has left had reverser, and I AutoQuad I think (Although bear with me as I know nothing about Green Tractors, far too expensive for me).

Anyway you start the tractor and all seems OK will move forward and backwards ok, BUT after about 2 mins will stop going backwards (then after a while wont go forwards). The only error code was Low Transmission speed, we did tilt the cab and change that sensor, BUT suspect that error is valid in that its erroring due to not moving....

Anyway the owner and another mechanic already put a new reverse solenoid on, and changed filters etc... and the 2nd Mechanic tested pressures on the gearbox and all seems OK, he also said you can watch all the pressures ramping up correctly but then it just doesn't move....?

The really odd thing is that you turn the tractor off and back on and then it moves forwards and back instantly OK?

Anyone else had this issue?

 

[Tractortech]

Now Then..
If you start it and go forwards, would it go all day?? Does it only stop driving after using reverse??
Is EPC306061.31 the only code there is?? You would have to look in the EPC rather than wait to see what on the display..

 

[Einstien]

Yes the guy that owns it drove it to mine which is 6 or 7 miles and didn't say it dropped out, but I haven't tested that, it's only come here due to wanting to look at it on concrete in a nice shed....

 

[Einstien]

I really don't understand the on off fixing it so easily but no error codes....

 

[Einstien]

061.31 and did get 057.31 once.... early on I think...

 

[Einstien]

Yes just checked - and I now note you loose forward as well as backwards - getting EPC360061.31 and EPC360057.31

 

[flywheel]

Where the mobile mechanics from John deere Dealer as some systems only work with correct john deere laptops etc?

 

[Einstien]

The second was a JD Specialist with Licensed Software and what seemed like lots of info on the laptop - he checked and validated everything and went through the diagnostic process too and didn't get anywhere other than saying everything seems OK from the software side of things....

 

[Einstien]

Another thing I do note - which might just be because I'm a Ford man is that the brakes are extremely sharp on it!

 

[Tractortech]

So, the enable signal is being lost causing the other code. This could be the enable pressure sensor on the front of the Powrquad just above the MFWD driveshaft or the wiring to it.. Also, has the wiring been checked around the rear RH cab pillar??

 

[Einstien]

Wiring checked, that sensor and a proportional valve of some sort checked too, front prop currently removed

 

[Tractortech]

The problem lies there somewhere.
Sharp brakes won't be the problem, they are power brakes therefore a different feel to what you're used to perhaps..

 

[Oliveau]

So complicated these days! My stepson has beeen an out & out JD man for 45 years but is now totally fed up with continual breakdowns, which are always related to the 'technology'. I've suggested [a bit tongue in cheek] that he imports some older tractors from USA - 4020 powershift would be nice or what about a nice Case 2294 MFWD I asked.

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[Tractortech]

Any news on this?? 🛠⚙

 

[Scholsey]

Our 6420 used to lose drive if idled in 4th splitter in any range, would drop into neutral and had to flick shuttle into neutral and gear into park and back out before it would find a gear again.

Apparently it was a common problem and needed something doing inside, P/X it for a bigger one with the dealer so it was there problem to sort.

 

[Tractortech]

Our 6420 used to lose drive if idled in 4th splitter in any range, would drop into neutral and had to flick shuttle into neutral and gear into park and back out before it would find a gear again.

Apparently it was a common problem and needed something doing inside, P/X it for a bigger one with the dealer so it was there problem to sort.

That would be a cracked direct drive clutch drum. Done a few..

 

[Einstien]

Owner has shipped it to the Mechanic's workshop now - I'll let you know what they find, I'm with you in that there is a wiring/corroded plug somewhere.... I had a good play with it in the yard - no amount of gear changing etc would get drive back once failed. But you can tell it wasn't going to move and stick it back to neutral quickly before the error on dash, then I'm pretty sure on one occasion I gave all the wires running round the pillar at the back a good but gentle push and movement etc, and it moved again for a short while without stopping and re-starting.

 

[Einstien]

The other thing is that apparently it only started not long after they had tilted the cab to repair an oil leak around some cooler, so obviously all the wiring had a bit of un-normal movement to tilt the cab.... Just strange the on/off fixing it... Watch this space

 

[Einstien]

So owner rang to say they have had it apart found some "half shaft bearing breaking up and going into the Autoquad box" Anyway cleared swarf out etc and seemed ok then did the same thing apparently....

 

[Einstien]

Sound like they are still leaning towards some sort of blocked oil route or blocked valve, very odd.......