Can anyone suggest what causing the problem on my daily pick up truck.

Its an imported Nissan Cabstar, with a Toyota 4y engine. When its stood running, there is no noise at all. The clutch depresses ok, and selects all the gears ok, but occasionally when its moving (Forward or reverse) in gear there is a grinding whinning noise. I can't seem to narrow the noise down. It sounds similar to the high pitch slipping alternator belt, with a low mechanical sounding groan. It appears randomly, and can be heard in different gears, but comes and goes.

It also occurs under engine breaking

I have checked the gearbox oil level. Any suggestions ?

Any idea how I can find out what the gearbox is from ?

Cheers

David

[Edited on 11/11/10 by Scoobythedog]

Have you tried letting it coast in neutral it could be diff, wheel bearing cv joint etc

Yes, It coasts in neutral fine, Its only happens when its in gear.