JCB 803 Dual Speed Tracking

[AndrewMawson]

Hi All,

My 1997 JCB 803 has dual speed tracking, or rather it ALMOST has dual speed tracking :)

One track motor does both speeds, the other only does low speed which makes for some interesting steering! As I under stand it, fixed to each track motor is a spool block with two spools in it. One is a 'balancing spool' and isn't involved with dual speed. The other is spring loaded to 'slow' and when the fast button is pressed, oil from the 'fast' solenoid valve pushes it to compress the spring and move the spool. When the spool moves it lets oil to the motor which up till now has passed though two orifices (hi torque) now only pass through one (high speed).

As the plumbing from the 'fast' solenoid valve goes to both track motor spool blocks it's reasonable to presume that it's working, but one spool is stuck.

Before I pull it apart I'd welcome any comments, or have I missed another possibility ??????

[Muz]

sounds feasible .. with the amount of burst hoses a JCB 'usually' has it could be a rubber fragment stuck in a pilot hole or spool although you'd assume reversing direction would clear that, but not in a control spool, so it could be a broken spring, or something ? Anything you can swap to the other side and see if it get replicated on the other side ?

[AndrewMawson]

When I have a couple of hours of play time the plan is to pull it and remove the spool and spring and give than a good clean. Hopefully I'll find its stuck and what's sticking it

[AndrewMawson]

Well it's fixed

And the fault was nothing like I had surmised. I stripped out the spool block, found that one of the four caphead bolts retaining it to the track motor had sheared off. Initially I though that this was the problem as the block would be slightly distorted possibly binding the spool but no. I helicoiled the female thread in the track motor put it all back together but symptoms remain unchanged.

Then it dawned on me, just possibly the fitter who replaced the Orbiter for me had reversed the servo feed and drain return on that side it would give the same symptoms. A right pain to get at the hoses on the orbiter, but no reason that I couldn't reverse them down at the track motor end, so I did that at crack of dawn this morning, and guess what, WE HAVE TWO SPEED TRACKING !!!

Before he changed the orbiter the tracks and sprockets were so bad that I'd not really tried fast speed. Tracks and sprockets have been changed now

[Muz]

Good news Those hoses at the orbital valve are always a pain because many are similar sized and length .. I always use coloured ratchet straps on them to identify the layers when I take them off

[ianoz]

.. I always use coloured ratchet straps on them to identify the layers when I take them off

Tip .Leave the zippy ties on for the next time it has to come apart .After the 3rd set of boom pipes on my JCB8080 that is what the fitter did .Total cure never had to touch it again

[AndrewMawson]

In fairness to him, he did use ties, but must have got confused when moving the adaptors from one orbiter to another. I fit ties, BUT I take a photo with my iPhone to avoid any confusion, like I did with these on the dual speed tracking spool block, but then I always was 'belt and braces' !!