B4 Diff Problems

[j pearce]

Hi,
I've recently rebuilt my B4's diff with new balls, slipper plates and thrust bolt. It seemed fine until last night when it began to make a bad clicking sound at 1 point in the rotation. Naturally, I whipped out the diff and had a look around. There didn't seem to be any problems other than very slight ware on the plates so I turned them over. The next race seemed fine but now it’s gone really slack and unpredictable. 1 minute it makes a bad scraping noise, the next its fine. In the same way, half the time the diff will engage when turning 1 wheel, and then it won’t...Does anyone know what might be to blame??? Thanks