I've read the "MB ball joints are different" dozens of times, but never an explanation other than "they're under tension at all times", or something.
So, zackly how are they different?
I don't recall the design details ever being outlined here. I believe they are also called "compression" ball joints. If your search finds any info please let us know.
vic
Added:
I stumbled upon this.
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I was organizing my desk and came across an old FedEx TSB on this very subject. That was a good reminder that I have long needed to post a Tech Alert.
Weekly phone calls from frustrated Sprinter owners facing expensive ball joint replacement during a State vehicle safety inspection was a very good reminder as well.
It appears that the majority of Sprinter ball joint inspections are being done incorrectly. And lots of money is being wasted by performing time consuming and expensive replacement of good ball joints.
The design of the Sprinter front suspension has the ball joints in constant compression, even when the vehicle is raised and the wheel is off the ground.
Traditional ball joint assessment methods are completely inappropriate for the Sprinter.
The factory recommendation (also FedEx recommendation): DO NOT even attempt the traditional method of measuring axial play (up and down play) by jacking of the lower A arm and then prying on the stub axle. This will likely show an 'alarming' amount of play which would result in a failing grade. Alarming for a traditional ball joint design but NOT the Sprinter.
Replacement should be considered only if the dust boot is torn (risk of contamination and loss of lube) or excess pivot friction or noise is present due to lack of lubrication (If the boot is not torn it is unlikely that lubrication will be an issue).
I recall reading of similar confusion in England when the national vehicle safety inspection (the MOT) was resulting in needless Sprinter ball joint replacements due to incorrect assessment. The authorities later issued a 'spec' (3mm if I recall) to quell the uproar but it still did not recognize the unique design, it only provided a pass/fail number the techs could apply using a traditional and incorrect measuring procedure.
Sprinter ball joint replacement is an ugly, difficult, and expensive job which, if done without care, can result in damage and also front wheel sensor issues.
Educate your local tech.
Doktor A
I was organizing my desk and came across an old FedEx TSB on this very subject. That was a good reminder that I have long needed to post a Tech Alert. ...
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It is not the construction of the ball joint itself but rather the design of the front suspension that the ball joint is mounted in, that calls for the unique inspection procedure.
Compared to the OEM ball joint a poor quality replacement ball joint may well flunk the approved inspection process prematurely (compared to OEM) but testing is same.
Flunking defined as loss of integrity of rubber boot which would allow ingress of moisture and/or egress of lube and/or excessive LATERAL play.
Doktor A