Jcb3c mk111 no forward movement.

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Hugh
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Jcb3c mk111 no forward movement.

Post #1 by Hugh » Sat Mar 20, 2021 2:43 pm

Hi. I have a lates 80’s 3c mk111 . I seem now to be having a problem getting the machine to move forward.
It was working ok when I first got it and now it’s playing up.I have adjusted the dump valve and it worked for a short period now of its seems to have given up again. The oil level is ok and it moves ok in reverse but not forwards. One thing I have noticed is that if you put the gearbox in neutral then put the shutttle lever into reverse you can’t get into gear ( like a manual gearbox if you don’t put the clutch down)
But if you do the same for forward it goes in no trouble. Is it a complete engine out strip down or a simple readjustment .

Cheers Hugh


essexpete
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Re: Jcb3c mk111 no forward movement.

Post #2 by essexpete » Sat Mar 20, 2021 3:12 pm

Ideally you could do with a pressure gauge on the test ports. I am no expert and always had help with these transmission but you have already eliminated some things. The torque converter must be OK and the transmission pump must be functioning (even if not 100%). The dump valve must be centring or you would not have reverse drive. I assume you are getting full travel on the forward/reverse cable operated spool? Assuming the latter is OK,then you have a fault with the forward clutch pack with perhaps wear or piston seal. I wonder if it is a seal as clutch wear, in my limited experience, give a little warning of imminent failure. Any of the latter and it will be shuttle out.
A couple of tips from the fitter who I helped years ago would be to jack up the machine on the legs and place a chunk of sleeper under the lower rear cross rail to the jack foot them just lower the machine onto the wood. This will give you more space underneath. After removing all the various hoses cables and gear lever the rear prop is removed. The engine sump will need supporting as the rear mounts will have to come off. Now, if I remember rightly, we supported the shuttle box on the 4 sided sump (the Guy had made a little cup for his trolley jack). The studs/bolt from ahead of the shuttle box were removed. The gear box and shuttle were then slid rearwards to leave behind the torque converter. once down on the floor the gear box was separated from the shuttle.
There are a few on here who will talk you through an overhaul or you might be able to do an exchange with someone like Vicary Plant in Leicestershire.
Our Guy recommended fitting a new pump as a matter of course, overhauled the rear pack whist in pieces and also replaced a large bellville washer (from memory).


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Re: Jcb3c mk111 no forward movement.

Post #3 by agrimax » Sat Mar 20, 2021 11:20 pm

I'll just add one small point.You say the oil level is fine but did you check with the engine running or immediately after stopping it? If you check the oil after the machine has been sitting for a while,the oil in the cooler, runs back into the torque unit and gives a high reading. They will also continue to work in reverse if low on oil(except if nearly dry of course),but not go forward.
Apologies if you already know this but a few have been caught out by not checking the level as above.If the level is fine then I'd say the forward clutch pack will be the culprit as Pete says.


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Re: Jcb3c mk111 no forward movement.

Post #4 by Gazzz » Thu Aug 26, 2021 9:46 am

Can I ask Agrimax what is the "cooler" that you refer to (oil in the cooler)? Cheers


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Re: Jcb3c mk111 no forward movement.

Post #5 by essexpete » Thu Aug 26, 2021 10:37 am

The cooler can be found in front of the rad.


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Re: Jcb3c mk111 no forward movement.

Post #6 by essexpete » Thu Aug 26, 2021 11:57 am

To add: if you still have a problem with forward but machine will reverse it may well be a problem with the forward clutch pack.


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Re: Jcb3c mk111 no forward movement.

Post #7 by Hillbill » Fri Oct 15, 2021 11:04 am

Is it a build 3 brockouse or build 5 powertrain? I had the same problem with my brockhouse & it was all down to a broken spring in the modulating valve. Less than a fiver from Vicary & back up & running again


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Re: Jcb3c mk111 no forward movement.

Post #8 by essexpete » Fri Oct 15, 2021 1:59 pm

Hillbill wrote:Is it a build 3 brockouse or build 5 powertrain? I had the same problem with my brockhouse & it was all down to a broken spring in the modulating valve. Less than a fiver from Vicary & back up & running again

Good point. I may have assumed it is a build 5 powertrain. :roll:


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Re: Jcb3c mk111 no forward movement.

Post #9 by Hillbill » Wed Dec 01, 2021 8:34 pm

essexpete wrote:
Hillbill wrote:Is it a build 3 brockouse or build 5 powertrain? I had the same problem with my brockhouse & it was all down to a broken spring in the modulating valve. Less than a fiver from Vicary & back up & running again

Good point. I may have assumed it is a build 5 powertrain. :roll:

He did say "dump valve" so I assumed powertrain as well, but you never kknow


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