Spray inside chassis with clear waxoyl with an extension tube on the gun. You might have to drill extra holes to get into so e places. Get that mask as well!
Keep the viscous. LR put it on there for a reason. Just make sure it's working properly. For a few quid just get a replacement Bearmach one like I did. Electric is more stuff to go wrong. Viscous is fit and forget. Take spare if you are worried.
I know this doesn't help but vehicles are not built for wading in deep water / mud - seen it too many times over the last 35 years. It kills them!
Good luck with getting your motor working properly again
Output shaft bearings? Wiggle the props near the gearbox end - with handbrake off, out of gear and use wheel chocks! See if there is any play. Start there.