1990 silohette steering popping

1990 silohette steering has a popping noise when turned . appears to be when it is close to stop on either right or left turn. does not happen when front is lifted off ground.

i would guess one or both cv joints have you checked the boots to see if they are cracked or torn they don't last too long once dirt and water gets inside the boots. also if the boots look good then shake the front tires with it jacked up and see if they move with your hands placed at 9 0'clock and 3 o'clock then at 12 o'clock and 6 o'clock then turn the tire forward then backward as far as you can by hand in park.something will be loose and have play in it.don't get under it with only the jack holding it up...

i almost forgot could also be the ball joint while you got it jacked up take a board or something at least 2 to 3 feet long and pushup and in on the bottom of the tire if it move in the balljoint is bad and i have seen them break and the car or van fall on the ground both times i seen were going less than 10mph but they can break anytime when the are worn out.