jcb 525 telehandler 2 wheel steering!?

we have broght a 525, which has the 4 wheel steer sytstem welded to front wheel steer only and the steering valve removed, my question is ?
we have replaced the steering valve block and re plumbed it in, replaced the steering control unit and cut of the welded in plates to the rear wheels , BUT
we can not get the front wheels to work we get 4 wheel steering, crab steering but no front only steering, jcb will not give us any help ie wiring diagrams or hydrolic pipe daigrams we can not afford £100 per hour for jcb fitter ! help any ideas welcome or info that anyone has please please