Preservative grease

[Ed Landstrom]

When dealing with new-old-stock parts, how important is it to remove the preservative grease and what's the best way to do it? The part I'm dealing with is an M135 differential, but I guess the answer would apply to anything with internal moving parts.

I'm not sure what the consistency of the preservative was when it was new, but 60 years on, it's like a stiff wax. Did the repair depots originally use a hot tank to remove it? I don't have one of those, and a couple of days soaking in my parts cleaner softened the preservative on the outside to the point where a stiff brush would remove it, but didn't make much impression on the internal parts I can't reach.

Will it have to be stripped down to clean it, or can it be effectively flushed somehow? How important is it to remove every last trace, including places I won't be able to scrub, like inside bearings? Will a small amount of residue dissolve harmlessly in the gear lube or will it cause problems?