Gear-type crunchy noise
 

:confused: Hmm, my Macnum gearbox has developed a strange gear-slippery crunch noise when accelerating. Lasts a couple of yards then goes, the car seems to accelerate OK otherwise. I pulled the box apart the other day, all the gear teeth were there, the diff seemed a little under-greased so I applied a little more, rebuilt to what I thought was tight, rebuilt the slipper and test - massive slip. Tightened the diff screw and all was well but the noise was still there. I've never built a ball diff before but I realise I can't over tighten it as I'll push the balls into the thrust plates. Any one got any advice?

Did you check the bearings whilst you had the gearbox stripped? Sounds like it could well be a knackered bearing,if the gear teeth are ok.

Check the thrust bearing

Is this the one behind the diff screw?

Yep, that's the one