Boys and Girls,

I recently had an alignment (and new tires) on my '02 V6. All work was performed by the local branch of a regional tire shop chain. The mechanic found the front left lower ball joint worn. He ordered a replacement but the outer diameter was a loose fit where it pressed into the steering knuckle. He said the car needed a new knuckle, but I was a bit confused as no relative movement (and wear) should take place between the knuckle and ball joint. Here's a view of a knuckle (ball joint at lower left), image shamelessly stolen from Amazon:





Fortunately, a second mechanic was assigned to help after a couple days of frustrating delays getting parts. He suggested the new ball joint may have been the problem, not the existing knuckle. Mechanic #2 ordered a different brand of ball joint and it fit perfectly. I do not know which brand fit and didn't fit.

Hopefully this helps if somebody runs into a similar situation. FWIW, Jaguar does not sell the ball joint separately, even though it's fairly easy to replace with the right tools. You have to go aftermarket if you don't want to replace the entire assembly.

 

Karl isn't that related to the ball joint diameter change from 14mm to 16mm?
I thought Jaguar made a running change around 2002 based on the SN of the car?
I "think" it was changed at SN M45254?

Here is some data from MOOG but they neglect to give us when the change over was done? But note the chart shows the 2002 S-Type can have either one depending on the VIN or SN.




Either your car needs MOOG K500084 with the 14mm stud or MOOG K500085 if you have the 16mm version.
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Unfortunately, I didn't get to talk directly with either mechanic. I can't imagine discovering a 2mm difference wouldn't make you go "Hmmm" and wonder if you had the correct replacement. Mechanic #2 said he had seen a similar situation with other cars, and the outer diameter of different brand ball joints was just a smidge different.

My car is pre-M45254. I'm not sure what the outside diameter would have been.

 

Pre M45254 should be the smaller 14mm ball joint. This is the stud diameter.
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