Yes, I’m occasionally on JU. You are right about the D-35c being somewhat noisy. Mine has always had some gear whine, even after the rebuild. At least the whoa whoa whoa went away. Anyway, I change my gear lube out every year because I pull a heavy boat. I have used Royal Purple 85W-140, Amsoil 75W-140, and Schaeffer’s #267 80W-90 (my most recent fill). By far, the Schaeffer’s gear lube is the quietest of the bunch (and it’s not even the right grade! - - should be using synthetic 75W-140 with the limited slip tow package). So, based on my ear-o-meter, I’d have to recommend the Schaeffer lube. You can check out its specs on the schaeffersoil.com web site. Check your yellow pages under oil to see if you have a local jobber, or buy off Schaeffer dealer on this board.
Here is my procedure.
1. Pull cover off and drain.
2. Scrape off gasket material and completely clean gasket surfaces (sometimes I have to use emery cloth).
3. Spray out differential with a full can of carb cleaner or brake cleaner (Berryman’s B-12 works great). Wipe out with clean cloth or good paper towels. Allow to completely evaporate (about 15 min).
4. Make a new gasket by running a bead of RTV Black (hi temp stuff) on differential cover.
5. Mount cover and gradually tighten the cover bolts, each one a little at a time. Once they are snug, tighten to spec using a torque wrench (use a star pattern).
6. Allow RTV to dry overnight before filling.
7. Next day, pump fresh lube into diff til full.
Good luck.