Hi, my daughters nissan micra has developed a noise in the gearbox in 4th & 5th gear only, sounds like a bearing, tried some thicker oil type products (no real improvement) but wondering do any of you have any remedies 'old or new' that i could try

, she's a student so funds are low and a replacement box is out of the question

. The car's only done 36k and everything else is great.
Any idea's my friends will be greatfully recieved
Thanks Izzy