Dear Imarukee,
We have had better performance recorded when Omega64, a semi solid grease (NLGI #00)was used in several similar gearboxes. This product is fibrous and stays between and lubricates the gears. You can get more info on the products if you will visit www.magnagroup.com. you can also write to them if you need to know the distributor details in Your area.
Best Regards
Collins David