squealing/grinding noise from drivetrain defender 110

hi all
wonder if anyone can help i have terrible grinding?squealing sound coming from my gearbox or transfer box when doing over 40mph in 4th and 5th gear just looking for any idea what it could be. also i have a rattling sound when car is sitting still from the gearbox/transfer box

cheers

Get help t on a ramp, put the it in 1st gear and let in run. Then go around with a screw driver and check where the noise is coming from before you start buying stuff