Noisy Gearbox????

[520i]

Hi, i have a 79 518 and am experiencing excess noise from what appears to be the gearbox. It sounds as if metal teeth are rubbing together so am wondering if the gearbox uses any oil. if so then where would it be added because i have no idea where to even look. The noise resembles a chain on a motorcycle riding over the sprockets. I know its not the wheels because i had the carpets removed to be replaced and while driving, put my hand beside the handbreak on the frame and felt very rough and warm. this occurs even with the engine off and out of gear, whenever the car roles basically. Any help greatly appreciated, Thanks

[bad man working]

If it’s happening when it’s out of gear then it more likely to be the diff to fill it with oil there are 2 plugs in the diff back plate you’ll need a 17mm Allen key and it runs on Castrol G728

[520i]

Ok thanks a lot, ill get on it this weekend and change it.