I have a fluid pump that I've used for brake fluid. I am going to tackle transmission and differential fluid drain-n-fills in semi-near future...any concerns about using same pump for all of these, assuming I do an OK job of cleaning between tasks? Or is danger of getting even trace amount of different fluid in different systems great enough that I should get separate pumps for some (or all?) of the changes?
Provided that the wetted parts of your pump are compatible with the liquid you intend to pump, and that you clean the pump well when changing to a different liquid, you should have no problem.
May I suggest that you use pure acetone to clean the pump? (Assuming the pump is compatible with it.) Acetone occupies a happy place between polar and nonpolar liquids in that it will mix with either. So it will mix with ether, ester, glycol and mineral brake fluids as well as motor oil, gear oil and hydraulic oil, gasoline and diesel fuel, and it also mixes with water, glycol antifreeze and alcohols.
If you clean the pump by pumping a small amount of acetone, then pump and discard a very small amount of the fluid you intend to pump, your pump will be ready for action without contaminating anything.
I wouldn't run the risk. If the pumps are cheap enough, and you're going to use them repeatedly, I'd buy one for each kind of fluid and label it clearly.
I have one for EP90 gear oil and would definitely not want to risk contamination to/from brake fluid.
These are about $25 each and thread into many types of 4 litre bottle. I keep a new-spare too.