JCB 3C back hoe

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percyhenry
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Real name: Robert Trull
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JCB 3C back hoe

Post #1 by percyhenry » Tue Apr 09, 2019 12:42 pm

9/4/2019
Hi please can anyone help with some info,
i was using my 1970 JCB 3C to pull out some trees with the back Hoe, afterwards it wont slew from side to side left or right.
with the rear bucket in the air i can push it from side to side
when i pull the leaver the hydraulics nudge the back Hoe both L & R but only a little bit, as if it has not got enough HYD power.
the slew pots are flat on the ends not rounded
i have taken the slew pot off, but cant see how to remove the piston and seals to inspect the rack & pinion.

Q
1 What might be stopping the back hoe from slewing side to side
2 how do i get it apart to inspect the rack ect
3 could it be something else

Any info would be a great help, im good with the tools, but not worked on JCB before Thank Bob


agrimax
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Re: JCB 3C back hoe

Post #2 by agrimax » Tue Apr 09, 2019 11:28 pm

I'd say the splines on the king post pinion which in turn mesh with the king post itself are worn out.

You'll see the splines at the top of pt no.5 in the diagram. This is for a mk3 but the mk2 is basically the same. The king post itself is slid down onto those splines.
https://parts.jcb.com/parts/index/part/ ... WY2In0%2C/

Been a while since I had a 3c(24 yrs and had the same problem back then) but if I remember right,there are 4 large bolts through the bottom of the slew actuator that hold it on to the carriage. With those undone,the actuator and king post will drop off the carriage and then the king post can be lifted up off the pinion.
If this is your problem,with the slew pot off,when you push the arm round by hand,the rack probably will not move.
Perhaps time for a complete replacement carriage/post etc........


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