Service and Install Ball Joints
Updated April 12, 2008
I just invested in a brand new set of Cepek 17" Aluminum wheels with Goodyear MT/R's. While my truck is driving nice and straight I figured I'd get the alignment checked just to make sure I get maximum tire wear. Not following my own advice I drove all the way to the shop only to find that I have bad front and rear upper right ball joints. No alignment today! I checked my records and found that 2 of the ball joints have around 55,000 miles and the other 6 over 60,000. I ordered out all 8 front and rear joints.
Pictured on the left is an upper ball joint and a lower ball joint.
Older Hummer Ball Joint History
Over the years AMG has made design changes in the ball joints. Note that sometime after the 1993 model year AMG made changes that required larger fasteners that secure the ball joints to the control arms. You will need to drill out the holes in the 'A' arms, replace the bolts, the washers, and the locknuts to use a new ball joint on an older truck.
You also should have 4 upper A arm reinforcement rings. These rings add 'meat' to the upper A arm where the ball joint gets bolted. The rings fit under the A arm and sandwich the end of the A arm when tightened. These parts don't come with the ball joint. Unfortunatly, AMG doesn't sell the rings, nuts, bolts and washers anymore. If you want to make one you can download this template. The rings are 1/4" thick steel.
Each New Upper Joint uses:
- 4 - 3/8 - 24 fine1-1/2" grade-8 bolts
- 8 - 3/8" grade 8 washers OD 0.7"
- 4 - 3/8 - 24 Top lock Grade C nuts.
Each New Lower Joint uses:
- 4 - 7/16 - 20 fine1-1/2" grade-8 bolts
- 8 - 7/16" grade 8 washers
- 4 - 7/16 - 20 Top lock Grade C nuts.
If you can't find the fine thread fastners you can use 3/8 - 16 and 7/16 - 14.
A "top lock" style locknut has a slightly elliptical hole. You can get the above bolts at any industrial fastner supply. You will have to make the reinforcement rings.
One of the problems with the original ball joints was the they did not have grease fittings. Greasing with a needle on the grease gun does not get to the bottom of the ball joint no matter how much grease you pump in (the proof was clear once I took the old one apart). Since the middle of 1995 all ball joints sold by AMG have grease fittings. If you some how get one without a fitting don't use it.
Maintenance: It is recommended by AM General that you grease all joints every 3,000 miles. In addition I would grease it after every major outing, or after you have been running in deep water. When greasing the lower ball joints you can jack up the lower "A" arm to remove the load from the ball joint in order to get the grease into the base of the ball joint. Pump grease into the joint until you see the old grease squirting out of the rubber boot.
It took me 6 hours to do all 4 front ball joints. I thought doing the rears would go faster but they ended up about the same. I had one lower ball joint nut that needed a torch to get loose.
This is a new style upper ball joint. Unlike the older ones this one has grooves on the ball so grease can work it's way to all surfaces of the ball. These ball joints all have grease fittings and can last over 100,000 miles. The one pictured had 58,000 on it.
Checking the Ball Joints
You can do a quick and dirty check of the ball joints by jacking the truck up on the frame so the A arms are hanging. Grab the tire at the top and bottom and shake the tire in and out while watching the upper and lower joints for movement. If you see any movement in the ball joints replace them. On a truck with good ball joints there will be no movement at all. I had a slightly loose upper right rear ball joint. My rear camber on the right was .2 degrees. The camber on the left was right on at .5. Replacing the ball joint should bring me back into spec.
The shop manual has a procedure that uses a pry bar that is much better. With the truck on the ground place the tip of a pry bar between the top of the geared hub and the upper ball joint boot. Pry upward against the upper control arm. You want to see if there is any free play between the upper control arm and the geared hub. If the ball joint moves more then 1/16" replace it.
For the lower ball joint jack the truck up by the lower control arm. Put a pry bar between the lower arm at the ball joint and the geared hub. Move the pry bar down. The free play shouldn't be more then 1/8".
In my opinion if the joints have any movement replace them.Page 2