There are a bunch of videos on YouTube for purging air @ the PS pump, BUT take some friendly advice & go buy 1 of those hand vaccum pumps from HF that are used for bleeding brakes & such. Just find a kit that has some generic rubber or foam adapters included. After you fill the reservoir, you will want to spend much time as possible trying to pull air out via vacuum before starting the engine & running the pump; you WILL, I repeat you will definitely run the pump dry for @ least 20-30 secs before it finally pulls the fluid. You can do a lot of damage to the pump in 20-sec & it does reduce the life of PS pump, considerably. There is a GM tsb for pulling vacuum @ PS reservoir before any other steps are taken because of so many pumps getting damaged as result of PS flushes with the pump running dry @ startup.
After you spend a few HOURS pulling air by vacuum, you will then jack the front tires up from the ground. With the reservoir topped-off and most of the air already pulled out, your assistant will be in the cab starting the engine & turning the wheels lock-to-lock about 10 x times while you observe the fill level & add as necessary. If you hear the pump whining for more than 10-sec @ startup I would kill it and try the hand pump a few more times. It also helps turning the wheels lock-2-lock even before you do the hand pump thing, front end jacked-up, key on, engine off, just trying to release any air from the gearbox after you fill it. Then do the hand pump, then have some1 else turning the wheels, engine off while you attempt to pull air with the pump & so forth. Whole point is to do whatever you can to get air out before ever starting the engine & running your pump with air pocket in it. It's not easy, very time consuming but highly necessary. But yes, the front tires should be off ground & turned lock-2-lock a # of times. Don't hold it @ full lock though for more than 2 secs. Make sure your helper knows this too before starting.
1 of my truck has a bleed valve on the gear box that I can open to pull vac' & get fluid running through the pump but even that isn't completely full proof; did you see anything like this on the gear box when you had it on the bench???
Another good tip is to loosen a hose clamp Or fitting before the gearbox if it doesn't have a valve that can be opened. You would pull or crack the hose/fitting open just like a bleeder valve to help pull the oil through the pump but I believe it must be full of oil or it won't prime. I would be trying to backfill it through the cooler or reservoir supply line with my hand pump if I somehow released all of the PS fluid in the remaining loop.
I also remove the fuel pump relay after filling up the reservoir so that I can turn the engine over a few times, seeing if that pump will pull the oil into the supply side of the loop so I can pull a vacuum downstream at my bleeder like I was referring to before. The hand pump, a bleeder valve, removing air pockets is all relative to how much or how little oil you have in the lines so don't STUF the pump! It's easy to do & will whine 'til the day it dies if you run it dry
