Scania GR905 manual gearbox problem

The 3 over 3 that I drove had a notchy 2nd, 5th and 8th, so all in the same place on the main box. I couldn’t get it without a crunch, fast, slow, double de clutching, the lot. I spoke to others about it and none of 'em reckoned much on the Scania box. Hope your fix ain’t too expensive.