The Chevy Astro van is equipped with the common GM Short/Long Arm (SLA) front suspension system. This system features unequal length upper and lower control arms that are attached to the steering knuckle by ball joints. As the ball joints wear, symptoms such as squeaking, popping while backing up, uneven tire wear and poor steering stability can occur. Checking the ball joints to determine the need for replacement is a simple procedure that can be accomplished by a novice home mechanic in about five minutes.
Place the transmission in "Park" or in first gear and apply the parking brake. Clean any build up of grease from the grease fitting on the upper and lower ball joints. Position the floor jack under the left front lower control arm and raise the wheel off the ground. Place a jack stand under the front frame of the van, but do not lower the floor jack.
Check for upper ball joint wear by grasping the top of the wheel and applying an alternating push/pull force while watching the upper ball joint. The standard used by the auto repair industry for determining if the ball joint is faulty is that "any perceptible movement with reasonable hand force" requires a replacement upper ball joint.
Place a large pry bar under the front wheel and pull up on the bar to force the wheel up while watching the lower ball joint. For the Astro, any movement in the ball joint of more than 1/8 of an inch requires a replacement ball joint. Some early Astro vans are equipped with a wear indicator built into the lower ball joint. To check these, lower the vehicle to the ground and look at the grease fitting. The boss that the fitting is screwed into is the wear indicator. It should protrude from the bottom of the ball joint. If it does not, replace the ball joint.
