Caution: The noises that occur when the seat belt is retracted are functional. If the noises are disturbing, the seat belt must only be replaced. Under no circumstances should oil or grease be used to eliminate the noise. The automatic seat belt retractor mechanism must not be disassembled, as this may cause the pre-compressed spring to jump out. Risk of accident!
Pull the seat belt out completely and check for torn fibres. Damage may occur, for example, if the belt is pinched or melted by a burning cigarette. In this case, replace the belt.
If there are abrasions without torn fibers, there is no need to replace the belt.
If the belt is difficult to move, check for twisting; if necessary, remove the trim from the middle pillar and route the belt correctly.
If the automatic seat belt retractor mechanism does not function, replace the belt
Clean the belt webbing only with soap and water; never use solvents or chemical cleaning agents.
(The original post is on the web portal fordbook)