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Thread: New Holland 7840sle gearbox help please

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    New Holland 7840sle gearbox help please

    I have a New Holland 7840 SLE tractor with about 3000hrs on it , it is the update model without the clutch cable.
    The tractor will only move very slowly and reluctantly in all gears and ranges accompanied by a grating or ratcheting noise, there is no fault codes showing and the trans pressure light goes out immediately after the engine is started.All the powershift gears work and change OK except that the tractor is just rolling with no real positive drive. I have calibrated the clutch fill times and they run right out to 210! The tractor main hydraulics are working fine you can load the engine up by fully extending a ram on the front end loader.
    I would be grateful for any help or pointers as to what may be wrong.

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    Re: New Holland 7840sle gearbox help please

    Quote Originally Posted by spanner1 View Post
    I have a New Holland 7840 SLE tractor with about 3000hrs on it , it is the update model without the clutch cable.
    The tractor will only move very slowly and reluctantly in all gears and ranges accompanied by a grating or ratcheting noise, there is no fault codes showing and the trans pressure light goes out immediately after the engine is started.All the powershift gears work and change OK except that the tractor is just rolling with no real positive drive. I have calibrated the clutch fill times and they run right out to 210! The tractor main hydraulics are working fine you can load the engine up by fully extending a ram on the front end loader.
    I would be grateful for any help or pointers as to what may be wrong.
    Have you checked the old chestnut problem of the control cable on top of the gearbox that is renowned for the socket head screws coming loose and/or the alloy sleeve unscrewing? At first guess it sounds like the shift collar is only being pushed into mesh a wee bit and giving drive as long as it can hold in there, too much resistance and the teeth could be separating giving you the ratcheting sound?

    Check that 1st and If right you'll owe me an ice cream from WA's best seller near the entrance to your 1 mile jetty
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    Smile Re: New Holland 7840sle gearbox help please

    Unfortunately nothing so simple , it certainly sounds like something like that but i have checked both the cables and even removed the cover plate and had a look inside, everything seems to be fully engaging !
    Oh and i'll buy you an ice cream at the foot of the jetty anytime

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    Re: New Holland 7840sle gearbox help please

    Quote Originally Posted by spanner1 View Post
    Unfortunately nothing so simple , it certainly sounds like something like that but i have checked both the cables and even removed the cover plate and had a look inside, everything seems to be fully engaging !
    Oh and i'll buy you an ice cream at the foot of the jetty anytime
    When you say its less the clutch cable I assume you mean its a Quad-mod - with the solenoid valves on the outside of the side cover? I think I'm right in that although its a lot simpler gasket than the earlier one it could still of blown? Means taking the side plate off but beside being able to check the gasket hasn't blown you'b be able to see a bit more?

    Odd that it move slowly in all gears? any noise from up the flywheel area? thinking of the drive coupling?

    Is 240 on callibration the top of the scale? Can't remember what would of been "normal" for that far back.......
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    Smile Re: New Holland 7840sle gearbox help please

    Yes it is the Quad mod box , pulling the hydraulic cover is probably going to be the next move . so far i have checked all the switches and the solenoids with an ohms meter and removed each hydraulic spool and checked them (did you know they are all the same ?) Have also removed and cut open the filters , all clean .
    The noise seems to be coming from directly below the cover where the two cables connect in at the top , maybe forward reverse syncroniser ?
    I am aware of the damper "clutch" on the flywheel but would that not affect the main hydraulics too ?
    Will keep you posted

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    Re: New Holland 7840sle gearbox help please

    Quote Originally Posted by spanner1 View Post
    Yes it is the Quad mod box , pulling the hydraulic cover is probably going to be the next move . so far i have checked all the switches and the solenoids with an ohms meter and removed each hydraulic spool and checked them (did you know they are all the same ?) Have also removed and cut open the filters , all clean .
    The noise seems to be coming from directly below the cover where the two cables connect in at the top , maybe forward reverse syncroniser ?
    I am aware of the damper "clutch" on the flywheel but would that not affect the main hydraulics too ?
    Will keep you posted
    Yes the damper drive plate totally packing up would loose hyds, I've had them break the tin plates and make tinny noises, but thats not to say they always fail like that.

    Can't see any reason spools shouldn't be the same. I'm fairly confident that the gasket on the quad-mod may of been what we changed on one of our 8340's once, it had the early type with a more improved modified type replacement then being supplied because of the gasket blowing out. I'm wondering if this would explain your long fill times?.

    Now although this will sound stupid, but if the noise is where you say it is and as a test of last resort, I'd consider removing the top lid- IIRC it may be fairly simple and flat- running it with this off will rust proof the cab interior so how about finding a bit of perspex/acrylic sheet, copy any bolt holes and fix in place so you can fire it up and see if you cane see anything jumping thru the oil being thrown around?
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    Red face Re: New Holland 7840sle gearbox help please

    Have actually tried running it with the cover off and yeah , its like a fountain ! I will be back on to it on Monday and try your suggestion with the perspex.
    Thanks for your help so far

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    Re: New Holland 7840sle gearbox help please

    Have found the problem , removed the hydraulic housing from the side of the gearbox and all is revealed C3 clutch outer drum has about 10 cracks running back along the grooves the engage the internal clutch disk teeth !
    The next question is , can I remove the C3/C4 clutch assembly through the rear of the gearbox with only one tractor split ?

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    Re: New Holland 7840sle gearbox help please

    Quote Originally Posted by spanner1 View Post
    Have found the problem , removed the hydraulic housing from the side of the gearbox and all is revealed C3 clutch outer drum has about 10 cracks running back along the grooves the engage the internal clutch disk teeth !
    The next question is , can I remove the C3/C4 clutch assembly through the rear of the gearbox with only one tractor split ?
    That is very unlucky if a genuine 3k hours.

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    Re: New Holland 7840sle gearbox help please

    Quote Originally Posted by spanner1 View Post
    Have found the problem , removed the hydraulic housing from the side of the gearbox and all is revealed C3 clutch outer drum has about 10 cracks running back along the grooves the engage the internal clutch disk teeth !
    The next question is , can I remove the C3/C4 clutch assembly through the rear of the gearbox with only one tractor split ?
    Thats a result at least. As for your splitting question, that needs someone more familiar with these, I did split one of ours for something, it may of been the one that had the cooler stat drop out and she cooked a lot of seals. Our then dealer at the time lent me all the special tooling to expand and fit the plastic ring seals and a manual! I'll ask a couple of fitters I know who may have an idea, but no promises.
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    Re: New Holland 7840sle gearbox help please

    Gearbox needs to come right out and a complete strip down to get the C3/C4 packs out. C1/C2 and F/R synchro pack needs to come out the front first and then carry on through to get 3/4 out the back. The sealing rings and piston seals etc will need replacing and the clutch plates properly shimmed,ideally with a dial test indicator. It really does need that special seal resizer tool to fit the plastic seal rings. They are easily damaged. I used a piston ring clamp but it wasn't really ideal.

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    Re: New Holland 7840sle gearbox help please

    Quote Originally Posted by agrimax View Post
    Gearbox needs to come right out and a complete strip down to get the C3/C4 packs out. C1/C2 and F/R synchro pack needs to come out the front first and then carry on through to get 3/4 out the back. The sealing rings and piston seals etc will need replacing and the clutch plates properly shimmed,ideally with a dial test indicator. It really does need that special seal resizer tool to fit the plastic seal rings. They are easily damaged. I used a piston ring clamp but it wasn't really ideal.
    Give that man an Ice cream !!
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    Re: New Holland 7840sle gearbox help please

    Quote Originally Posted by agrimax View Post
    Gearbox needs to come right out and a complete strip down to get the C3/C4 packs out. C1/C2 and F/R synchro pack needs to come out the front first and then carry on through to get 3/4 out the back. The sealing rings and piston seals etc will need replacing and the clutch plates properly shimmed,ideally with a dial test indicator. It really does need that special seal resizer tool to fit the plastic seal rings. They are easily damaged. I used a piston ring clamp but it wasn't really ideal.
    Thanks very much for the info . I was a bit afraid of that have rather limited workshop facilities , Am guessing the cab will have to come off ? I may be able to borrow the seal resizer as have fairly good relationship with local NH dealer also i already have the luxury of a workshop manual.

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    Smile Re: New Holland 7840sle gearbox help please

    Quote Originally Posted by Footsfitter View Post
    Give that man an Ice cream !!
    Thanks for your interest and help with this

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    Re: New Holland 7840sle gearbox help please

    Quote Originally Posted by essexpete View Post
    That is very unlucky if a genuine 3k hours.
    Only owned the tractor for about two years but it appears to be pretty genuine low hours neat and tidy ! very little signs of wear on the drawbar and linkage.At the time of the failure it was only operating a what we call a slasher or pasture topper and that is really all its done for the last two years .The failure is really a mystery .

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    Re: New Holland 7840sle gearbox help please

    It's a few years since I was in the 8240 I had.It was a prequad but wouldn't have been much different as far as gearbox removal is concerned. I think the first time I removed the gearbox,I split at the engine,wheeled it forward and then removed the box.Next time I split at the rear of the box first and wheeled everything forward before removing the box from the engine. I supported the front of the cab on acroprops,removed the front brackets and screwed the props up to tilt the cab. Nearly sure the pick up hitch linkage at the rear of the cab had to be disconnected too,to allow the cab to hinge at the rear. When you go to refit the box to the back end,take the round plate off the left side of the transmission tunnel.It's behind the diesel tank,although you'll need it off too anyway.There is an idler gear on the back of the gearbox that has to mesh with the hyd pump. You need to look/feel through that plate hole to make sure the gears mesh otherwise the gear will break.........speaking from experience said he who had everything completely rebuilt and the wheels on only to have no drive,steering or hydraulics and had to split it again at the back to replace the gear that was broken in two.........................

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    Re: New Holland 7840sle gearbox help please

    Quote Originally Posted by agrimax View Post
    . . . speaking from experience said he who had everything completely rebuilt and the wheels on only to have no drive,steering or hydraulics and had to split it again at the back to replace the gear that was broken in two.........................
    That is the type of "lessons learned" that makes this forum invaluable

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    Re: New Holland 7840sle gearbox help please

    No wonder a rebuild without diy is so expensive. Would it be easier to remove the cab completely?
    Another option might be to carry out the basic legwork but let a pro do the rebuild of actual internal? Would it be sensible to either replace of carefully check the syncros?

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    Re: New Holland 7840sle gearbox help please

    Brake pipes,handbrake cable,more wires and rear cab mounts diisconnected and the cab is ready to remove but it's more work and little benefit to take it off.Just as handy to tilt it back a bit. The front clutch pack would need to be dismantled and checked out as well and at the very least,a set of those sealing rings and piston seals fitted.And also the f/r syncro hub, although if there has been no crunching to date,it may be ok.
    A proper gearbox rebuild by a 'pro' could easily run into 4k............That's not counting time removing and refitting it and replacing oil and filters.........

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