Originally Posted by AmiSMB

It would seem you have a problem on your top layshaft. Check to see if the heads of the screws that go all the way through the gearbox are protruding past the motor plate. These screws should have thread lock on them and only done up finger tight so that the head of the screw just mates up with the plastic on the outer of the gear box casing. Next check the aluminium spacer. Durango made a running change to a hard anodised one. The original one which I have is not and when you tighten the slipper the spacer ends up riding up the layshaft where the gear should be binding the shaft. I dremeled mine down and placed a 8th clutch shim either side. Make sure that there is a 3mm washer at the end of the layshaft before the spring goes on as if this is missing the spring will bind up against the bearing. You also need to check the inner slipper plate and see if it is binding on the motor plate and if it is you will need to place an 8th clutch shim after the bearing before the inner slipper plate. I use AE slipper pads as well as they are thicker than the Durango ones but make sure that they are inserted so that they are flat in the spur otherwise when the spur gets hot the spur will move and then strip. When you have the gearbox and slipper built make sure that there is a very slight amount of play in the shaft which should exist even when you tighten up the slipper nut. I put a 2mm washer after the spring and before the nut as well. Hope that helps.