WD40 should not be used as a lubricant. It does container oil but it also has a lot of solvents which will wash away other lubricants.
It also isn't a great cleaning agent, brake cleaner works beter and leaves no residue.
The chirping is probably the driveshaft joints, not the motor.
You could clean the parts and apply some marine grease or MoS2 grease, but on those exposed joints any greasy lubricant is likely to pick up dirt and make wear on the joints worse.
Best is a dry lube like graphite powder or learning to live with the noise.