My 92 S-10 just hit 30K miles (yep, no typo, 30K), so working my way around complete fluid exchange on the vehicle. The Power Steering is the only factory fill left. Like many rear diffs, there is not a drain plug, and I **really** didn't want to mess with removing the cover, gasket scraping, etc. I know, its not **that** big a job, but its not leaking, and I want to keep it that way.....I've had lousy luck in the past when removing pans, valve covers, etc, and fighting leaks after. So, I bought a cheap suction pump, a gallon of Super Tech 80W-90, plus a quart squeeze bottle of the same gear oil (saved a few bucks doing it that way, just keep refilling the squeeze bottle). Removed the fill plug, added some gear oil so see how low it was, maybe 1/4 quart....not bad for 17 years, IMO. I drove around a bit to warm things up, then was able to pump out just under 2 quarts after fishing the hose as deep into the diff as I could. I then filled it, and plan on repeating this procedure after a few hundred miles. This should give me a good majority of oil replacement. Not sure of total capacity, but can't be much over 2.5-3 quarts, give or take, so looks like I got a good majority pumped out removing 2 qts. So, any real disadvantages to doing it this way (besides not being able to inspect the diff gears, but I'm not experiencing any problems with it), because if I had a drain plug, which some diffs have, it would be about the same thing, right? I still would not be able to inspect, or wipe the cover off, clean sludge out, etc. Pump cost: about $7 at Wally World, not too much more than a gasket and RTV. So, my question is, why don't more people use a suction pump, it seems to me a way easier way to change or refresh the rear diff oil. PS: The Haynes manual for the S-10 4WD version says using a suction pump is the only practical way to change the front diff oil. I have to take their word, since I have 2WD.