whirring coming from gearbox?????????

Hey all,
After a bit of info…. Im the proud owner of a Mk1 Karmann Cab in silver and after treating her to a new hood last weekend have now noticed a whirring noise coming from what seems to be the gearbox when im driving forwards! its slightly louder when in 1st and 2nd but is still present but not as noticable in 3rd up to 5…
She goes into all gears fine by the way,
also had a new clutch fitted in January and a major service
Any ideas or info would be greatly appreciated
many thanks and see you all hopefully at the gathering in july!!!!  

welcome to the club,have you checked your gearbox oil level? better still,drain the oil and put fresh in,if the bearings have gone though its a rebuild time,
Bert