Chris, on the gear oil, I found this in a Yesterday's Tractors forum:

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Topic: Re: GL1 Oil
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buickanddeere
08-23-2005 13:34:03
216.183.136.2
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GL-1 is a gear lube without additives which can corrode copper based bushings.
For improved lubrication GL-4 Marine, not just plain GL-4 works well. It&quot;s high pressure additives do not corrode copper based metals should some water end up in the gear lube. 
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I don't know whether there are any brass or copper parts in my transmission.   There was a brass bushing on the PTO shaft, but that is gone since I replaced the mechanical lift with hydraulic.

Maybe I should just go with GL-5 -- but if you have any more info or thoughts let me know.

Tom