Engine Oil in Trans & Transfer Case.
Hi Nick,
With all due respect, you may want to investigate that option a bit more.
I've read on the BITOG (bob is the oil guy.com) website, that engine oils are not a good match for many transmissions. I believe it has to do with the additive packages in the different gear oils. They are formulated for each different transmission depending on what the transmission requires to protect things like synchro's, etc. The wrong gear oil will cause excessive wear on things like brass synchro's.
I'm not a very "mechanical guy", like you are but, I do spend too much time reading this stuff. What you mentioned "raised a red flag" & caused me to remember reading about just this thing. I hope you don't mind me suggesting you look into this idea a little further.
Joe F. (Buffalo)