Vacuum fluid extractor for tranny/gear oil?
 

I recently switched from jacking up for oil changes to using one of those vacuum globed oil extraction pumps that feeds into the dipstick neck. It's advertised as being able to be used for extracting other fluids ... which fluids can safely be extracted on an 8 with this method? Does extracting brake fluid cause bubbles to get into the lines?

When I've jacked up to swap gear and tranny oil, I know to just refill until it leaks out the drainage plug. When using an extractor, how do you judge how much to refill after extraction without overfilling?

Measure what you take out