Strange noise in third gear ?

[tarquin]

Hey chaps, I am running a 4 speed box in my escort which has started to make an odd whining noise in third gear, the sound is like when a diff is running low on oil.
I have checked the oil level in the box and it is level with the oil plug.
This noise only seems to be in third , and non of the other gears, does anyone have an idea what it cold be ?

Thanks in advance

[Escort TC]

Mainshaft Bearings

[tarquin]

Ag crap , got to take the box out ,

Cheers thanks for all your help mate

[Graham]

Mainshaft Bearings

yep i'g agree with that