I have older trim pumps (late 80's) TRS setup w/ trim and tab pumps that do not have the separate reservoir. Do the drives / tabs need to be in a particular position (all the way up / down ) to correctly check the levels? Also what type of fluid should be used - brake / hydraulic fluid ?

Thanks!

Drive should be all the way down, tabs should be all the way up. You can use hydraulic fluid or motor oil. Never brake fluid.

ok thanks.

What if I don't know what's in there, is it ok to mix hydraulic fluid and motor oil, or do you need to drain / bleed the system? If so that will be my next question - how to bleed?

Thanks.

I would not mix them, a friend of mine had mixed and his fluid started to gel and get thick, bleed by operating unit up and down a few times and keep fluid level to the full mark

Ok - I guess I should of asked how to drain these pumps 1st!