Thwaites dumper stalls

[Amateur]

Old 5 stud 6 ton Thwaites dumper refuses to move forward or reverse. Engine runs fine.
When I turned off the key & started the Engine it moved forward for 1-2 minutes,
then it stalled. It now refuses to move even with stopping & starting the engine.
How should I locate the cause of this issue i.e. what should I test first,second,etc?

 

[Lincs Lass]

Is the handbrake seized on

 

[Amateur]

no, I recently removed the mechanism because it needs replacing.
I presume its electrical and I was wondering if there is some quick way to short circuit the electrics to engage the gearbox.

 

[Pheasant Surprise]

Forward and reverse pack solenoids both engaged?

 

[Amateur]

I have not attempted to locate this problem yet so I don't know the answer to your question.
There is a pack of 3 relay switches under the dash, I presume this is what you refer to "solenoids"?
see pic.
Which relay is for "Forward" and which relay is for "Reverse" ?
How should I verify engagement for "Forward" ?

 

[Kevm]

Those are relays, maybe for fwd/rev, easy way to tell pull them out one at a time and see what happens.
The solenoids are on the gearbox somewhere and you could pull the connector off them to try the same thing.
could be a mechanical fault in the actual box though.

 

[Pheasant Surprise]

Could even be the switch in the power shuttle stalk.

Have you got a meter and test lamp to check your electrics with @Amateur (that sounds so insulting )

 

[Pheasant Surprise]

So.....not intimately familiar with your model, but in general I’d logically follow this process:

1. Test the switch on the stalk. Check you’re getting a 12v feed to the switch from ignition live, and it’s passing 12v to the relevant forward or reverse relay wires.

2. Test the relays, as noted above. Check 12v present as you switch the stalk. Swap the relays over to the alternate position and retest.

3. Test the solenoids on the side of the box. Follow a similar process and swap solenoids over, and see if the problem moves.

As it’s affecting both forward and reverse it sounds a common problem to both circuits if indeed it’s electrical - so check your earthing and 12v feed via the ignition switch is good.

 

[Amateur]

Thanks guys. I have a multimeter and can carry out the checks suggested.
I am not on the farm this week so it will be the next week before I get around to carrying out the suggested tests.
I have photos on my laptop which i took during the summer while replacing filters and wondered what the object pointed to by the screw driver was. I now believe these are the solenoids you guys are referring to, see attached.
This seems like some sort of solenoid pack, to eliminate a faulty in the pack, can I remove it and manually engage forward & reverse with a screw driver?

 

[Zetor]

Thanks guys. I have a multimeter and can carry out the checks suggested.
I am not on the farm this week so it will be the next week before I get around to carrying out the suggested tests.
I have photos on my laptop which i took during the summer while replacing filters and wondered what the object pointed to by the screw driver was. I now believe these are the solenoids you guys are referring to, see attached.
This seems like some sort of solenoid pack, to eliminate a faulty in the pack, can I remove it and manually engage forward & reverse with a screw driver?

Yes they’re the f&r solenoids but you can’t manually engage drive but you can test the cable to it for power with a multi meter.
Check the dump pedal, it’s like a clutch and in the position of the clutch on the floor it activates a micro switch and disconnects drive, it could have seized up and stuck down and you’ll end up with no drive (common problem) or check the micro switch the dump pedal operates.

 

[Amateur]

So, my intention is to bypass relays, micro switches etc by connecting 12 volts to the one of the solenoids to see if it moves backwards or forwards. It is unlikely both solenoids are faulty, If it does not move backwards or forwards then the problem must a either be a total failure of the switches or the fault is in the actual box ?
This also raises the question how do I actually test the solenoids function correctly?

 

[Pheasant Surprise]

Check the solenoids are OK. Resistance check. See video.

Check you are getting a 12v feed into either solenoid from the loom going into the solenoid connectors when you engage forward / reverse ?(very carefully!)

 

[essexpete]

Useful the last post.

 

[Amateur]

very informative. Next Question!
A starter solenoid causes a mechanical movement of a small bar (I dont know the correct term here) to connect the voltage from the lug connected to the battery to the stator windings of the starter.
Are these dumper solenoids providing voltage/current to some electrical gadget in the gearbox or are they moving some mechanical device?

 

[Pheasant Surprise]

very informative. Next Question!
A starter solenoid causes a mechanical movement of a small bar (I dont know the correct term here) to connect the voltage from the lug connected to the battery to the stator windings of the starter.
Are these dumper solenoids providing voltage/current to some electrical gadget in the gearbox or are they moving some mechanical device?

They are operating the spool valve which is in the middle of your last photo. The spool valve then either engages the forward or reverse clutch pack by applying (pressurised) oil to the respective pack.

 

[Amateur]

thanks.
as a matter of interest if I place my hand on the spool value between these solenoids can I feel any physical movement? Can the spool value itself be fault ? How does one test the spool value?

Assuming the solenoids & spool valves are working, How does one determine whether its the torque converter or clutch packs in the gearbox ?

 

[agrimax]

If you find the solenoids are receiving power and working ok and that the spool is moving freely both ways when shifting the shuttle lever/switch,you may find that a gasket has blown. The 4 cap head screws that retain the solenoid block need removing(they tend to seize in the block and are easily sheared, so tread carefully) and the block lifts off. Couple of o rings under it. Then the aluminium block comes off and there is a special gasket between it and the transmission housing. It could have a blown section causing the problem. Looks very like a JCB synchro shuttle transmission you have............

 

[Pheasant Surprise]

Looks very like a JCB synchro shuttle transmission you have.........

Probably is an ITL box (aka now JCB Powertrain) in it. Thwaites tend fit a lot of power-shuttle, power-shift and transfer boxes made by ITL out of Wrexham.

 

[Pheasant Surprise]

thanks.
as a matter of interest if I place my hand on the spool value between these solenoids can I feel any physical movement? Can the spool value itself be fault ? How does one test the spool value?

Assuming the solenoids & spool valves are working, How does one determine whether its the torque converter or clutch packs in the gearbox ?

Well when you’ve exhausted the other likely candidates in the electrical realm, and others as noted in the posts above.....it’s really time to reach for a workshop manual. Transmissions are a world of pain if you don’t know what you’re doing.

 

[Pheasant Surprise]

@Amateur - It’s really worthwhile getting a hold of the workshop manual for your machine and getting familiarised. Offset the saving of doing it yourself and you’ll have the requisite info all there.

These aren’t particularly complex machines, but access to wiring diagrams and hydraulic circuit layouts etc make DIY much simpler.