How to put in a tranny filter on a 91 gmc 4x4 4.3l blazer

Remember safety at all times. You will have to get under your vehicle. Wheel blocks, jacks, wheel ramps, jack stands, or what ever, safety, safety, safety.The filter is inside the transmission oil pan. Have a catch pan ready, you may have a drain plug so drain via plug, if not remove pan bolts from rear of pan towards front of pan leaving a few bolts loosened but not removed, at front so pan doesn't drop down and spill oil all over you and surrounding area, loosen pan from trans, tilt pan towards catch pan and empty of oil. Remove remaining bolts and drop pan. Remove filter from bottom of trans ,you will recognize when compared to new filter. Be very, very careful in removal so you can reinstall gasket, or O ring and filter correctly. Clean gasket material off trans bottom and trans pan, replace trans gasket on pan ( TIP ) screw corner bolts thru pan and gasket for easier installation, get pan started replace other bolts. Tighten bolts in zig zag fashion, fill with proper trans oil marked on dip stick. Start and run vehicle till warm, top off oil, but don't over fill.
Just a little advise, if you've never done this before , it is a very messy job, you may want to take it your local repair shop where they can also make adjustments as needed, IT'S WORTH THE MONEY and you may wish you did. GOOD LUCK FRIEND.

You remove the transmission pan and then remove the old filter. Make sure you remove the old seal out of the valve body and install new filter with new seal and re-install pan. Fill with fluid and you are done.