[TowerTalk] US Tower seized gearbox

[Robert Harmon]

The original lube in the Hub City gearbox is 90W petroleum based gear oil.
They recommend using Mobil Synthetic Gear Oil SHC630 when changing the lube.
It is also 90 W.  The gearbox should be drained and flushed with a 
recommended
flush oil before putting in the new synthetic oil.  (Hub City's 
instructions are below)
When I did this conversion the new synthetic lube had a dark brown 
color, I called Hub City
and asked them about it and they said I needed to suck out the remaining 
flush oil
in the bottom of the gearbox before putting in the new lube.  The drain 
plug on the
bottom doesn't drain it all out there is still about 1/2" of lube in the 
bottom.  I drained it
again and stole my wifes turkey baster with the squeeze bulb and sucked 
out the remaining
lube.  I put a short stub of plastic tubing on the end so it would reach 
inside.  It worked great.
(I bought her a new turkey baster hihi)  After refilling again with the 
new synthetic lube and ran
the gearbox for a little bit the color was almost clear, just a slight 
amber tint.  Hub City says
our usage is different than the typical usage for these worm drive red 
gears.  They said most
of the ones are used in continuous duty for conveyer belt drives etc.  
Our non continuous
use should give us a long service life.   We still need to change the 
lube periodically.  I am going to change mine every three years.   I 
neglected the gearbox for a long time,  was focused on
greasing all the fittings on the tower.
73,
Bob
K6UJ

Here is Hub City's flushing procedure

http://www.winsmith.com/documents/Mobil_Glygoyle_General_Flushing_Procedure.pdf