1996 GMC Jimmy Lower ball joints

And since this is a 4WD you will also need to pull the drive axle out of the front hub. With it in place there is not enough room to get the steering knuckle off the ball joint stud.

The easy way to do the lower is to jack the vehicle up so you have access. Put the jack under the A arm right at the inner edge so that the suspension doesn't droop all the way when you jack it up. Toss a jack stand under the frame, but don't let the jack all the way down, just enough that the jack stand touches. Pull the tire off then break the axle nut loose and remove it. Next us an air hammer to shear off the rivet heads next to the bad ball joint. Pull the cotter pin OR just shear it using a good wrench. Then remove the nut. Next free the stud from the knuckle.

Now for the fun part. Use a rubber mallet or dead blow to knock the axle back enough that you can get the knuckle loose enough to get the ball joint out. Then CLEAN off the rust and crud that was under the old joint. Now test fit the new one. MAKE SURE THE GREASE FITTING is accessible before you bolt it in place. If it is OK then you can bolt it in. If it is too close for the grease gun to fit, use a die grinder to open the access hole larger so the gun will fit. Now bolt the knuckle up and torque the axle nut back in place. Check over all the bolts. Put the tire back on after checking the upper joint, tie rod ends and idler arm. Grease as required or replace as needed.