NH T8040 has lost forward / reverse

[Farmer Roy]

Hi, just wondering if anyone has any experience with this.
NH T8040 tractor with 18 x 4 powershift transmission, over 8000 hrs
Started tractor, reversed away from where it was parked, pushed lever into Forward position & lost all drive, Forward & Reverse.
Steering, linkage & remote hydraulics all still work.
When you put it in Forward or Reverse, you can hear the engine change note slightly & when you let out the clutch you can feel a slight surge of movement, but that is all.
Threw up some error codes which pointed to the arm rest controller & the dealers lap top couldn't communicate with controller.
Replaced arm rest controller at many 1000's of $$$. That got rid of error codes & allowed communication with lap top, but didn't solve issue.
I'm wondering if it could be an issue with the bank of control valves on left side of transmission, behind the fuel tank, or an internal problem ( $$$$$$$$$ )
Its been down a week now & all dealer can suggest is to take it into their workshop 100km away & split it . . .
Apart from the actual logistics of that, am also very mindful of the cost of this
Any suggestions ?
Thanks

 

[cosmagedon]

Strange as it sounds like you've got multiple problems popped up simultaneously.
Have you tried calibrating the transmission? That would be the first thing I would do to see what errors pop up, then I would check the flywheel sensor, if you loose that on the older models I know you lost all drive. Those are the first easy things I would do.
The fact the arm rest controller failed is worrying though, the only time I've had a ECU fail is when the wiring rubbed through. Maybe lift the floor out and have a look/feel over the loom, have a look at the multiplugs connecting the cab to the main loom, I've also had these pins push out on the newer models.

 

[Pheasant Surprise]

As you say, ECU's generally don't fail of their own accord. Despite what some may believe they are very reliable and fail when something serious "external" typically buggers them up.

I'm with @cosmagedon on this one and be carefully checking loom and connectors for an intermittent short/rub-through somewhere. It doesn't sound mechanical to me.

 

[Beowulf]

I would go with the wiring fault theory too.

No experience of it on tractors, but plenty of experience of that sort of thing on cars. In one memorable occasion, mice/rats had chewed through the fuel injection loom on a friend's Lambo, resulting in me removing the engine to get access to it after the dealer had thrown parts at the thing in the foolish belief it was always what the codes told them.

 

[Farmer Roy]

yeah, the indicator on the instrument cluster shows forward / reverse etc when you move the lever


the mechanic claimed trans oil pressures were ok, but I don't know if he was just going off the instrument cluster or actually plugged something in


a google search has shown up possibilities ranging from a blown o ring in the valve / control block, wiring loom issues, faulty flywheel sensor etc etc


dealer not getting any info from plugging laptop in so seem at a loss


it sucks to be in the agricultural industry in a drought in a mining area - local dealer currently has NO mechanics, next closest is 100km away with only 1 bloke ( the workshop foreman ) with any experience with these tractors, & he's not coming up with any solutions

 

[Deerefarmer]

Can't like that Roy

Can you access the flywheel sensor and take an ohms reading from it?
Under the cab is there a cluster of wiring loom connectors, maybe could be accessed through the cab floor? and checked for bad connections?
Hope its something simple

 

[patrick4]

If it happened with no warning it is most likely one of the two speed sensors /flywheel input or gearbox output sensors the fact it tries to move is one of the symptoms had this a few times with new Holland TM and case IH puma and older 70 series new holland , it is very unlikely it's ECU lots of other stuff would be effected, . if transmission fuse not blown its unlikely a short to ground. It's a process of elimination .

 

[TripleSix]

Are the clutch pedal switches ok?