Sure, if the drive and prop shafts have seals on them to keep the oil in and the water out. Otherwise you’ll have to check the oil after every run. A good grease to use instead is John Deere Corn Head Grease, P/N AN102562. It works well in water and becomes fluid when worked so it gets into all the bearings and bushings. Regular grease can’t do that. In fact, I just drove 200K yesterday to a JD dealer to buy a case of it. Highly recommended for non shift gearcases.
https://www.greenpartstore.com/John-Deere-Special-Purpose-Corn-Head-Gun-Grease-AN102562.html
