[TowerTalk] Crankup tower gearbox lube question

[k4zrj at bellsouth.net]

I have an old Tri-Ex HZE-354 motorized crankup tower with a 40:1 ratio gearbox turned by a 1 HP motor. When I bought the tower, the gearbox was empty - no oil or grease of any kind inside - I guess from the staining on the gearbox, it had leaked out over the years. I have filled the gearbox with a mixture of SAE 90 gearlube oil and black lithium grease. It turns quietly and smoothly and leaks very little. There is a pressure relief fitting on the top of the gearbox.

My question is this: what do others recommend in this situation, and what do the manufacturers of towers fill the gearboxes with - lube oil like SAE 90, lighter weight oil like SAE 30, gear grease? The gearbox does get warm when lifting the tower and I'm a bit concerned that the lubrication could be improved. The tower goes up and down quite often, four or five times a week depending on how many thunderstorms we have. 

Thanks guys for your comments - always appreciated.

73, Charles, K4ZRJ, Woodstock, GA