Luey.
If you can now hear a noise from the gearbox that wasn't there before the oil change, then something has clearly altered. Whether that is caused by damage, a different oil specification, lack of sawdust (look it up if you don't know what I mean), or a vivid imagination, it should not be ignored. Normally I would have no qualms about using a cheap oil if it met the manufacturer's specification, but if you have doubts about the oil quality the first thing to do is to change it.