On my ol' 1951 truck with a non-syncro 4 speed,I drained it and re-filled it with fresh 90wt and added 2 cans of STP;that made a lot of difference,then I put down some sound proofing and carped in the cab. that did the trick for THAT truck;being a Brownie though you should find out what oil is recommended for it. I'm sure there's some kind of additive that would help. I'm going to try changing my own Brownie over to synthetic 50W oil,and I'm installing a trans. temp. gauge so I can monitor it for a while. (Might turn out to be a bad move,but I've been running synthetic engine oil of a similar viscosity to the OEM oil in the Transfer Case of my Bronco II for a couple of years of HARD use,and it's still working great.) This is only how I'd play it,you should check with the oil manufacturers and see what best fits the requirements of your transmission before you make changes.
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