W123 Mercedes CV Boots and Axles

Cracked CV boots are nothing new, but replacing them can be costly, and the axles might not warrant the time or money if the milage is high enough or the boots have cracked. Reconditioning an axle in uncertain condition will likely not serve you well in the long run and could easily lead you to spend even more money having to install new axles in the end. Instead, consider replacing the axles. Wait! It's not as hard as it sounds!

Mercedes-Benz used two types of axles, homokinetic and annular. According to Mercedes, the W123 could have either axle depending on the year it was built so make sure you check your vin and the axle itself before you make a purchase. Regardless, if you are in need of new CV boots with original high milage axles, this would be the time to move ahead with replacing the entire unit.  If your chassis is already fitted with annular, the job will be that much simpler. 

So what's the difference? What's better? Why convert? Who cares?

The difference between homokinetic and annular is how it functions, and that is a subject we will not cover here, but we will cover how they differ with regard to installation.

The following image shows the Mercedes-Benz OE annular axle along side the aftermarket axle that is a cross between an annular and a homokinetic based on the one piece design. The Mercedes axle as you can see requires a "flange" sitting separate from the axle which will be permanently installed in the differential making for a much simpler repair or replacement in the future.

At this point you have several options for this job. First, you can purchase a rear axle flange (needed for conversion from homokinetic to annular) and annular axle from Mercedes. Second option, purchase an aftermarket or refurbished homokinetic unit. Third option, install an aftermarket unit.

Is one better than another? If you are purchasing MB annular axles (homokinetic is no longer made by Mercedes), you are getting an excellent product, the same quality that has probably lasted 40 plus years. Should you go the direction of aftermarket or rebuilt, you run a good risk of noise, vibration and a much shorter life span.

After much research, I purchased what I believed to be the best aftermarket axle on the market, and unfortunately had my slight bubble of hope burst by what I saw, felt and heard. In fairness, it didn't appear all bad, but nothing I would want on my car. Ultimately I wanted to see if a $160 aftermarket axle could by chance prove good enough, and sadly it did not. Most often the old adage holds true, "you get what you pay for".

In brief, the new aftermarket axle right out of the box had a tremendous amount of play in each joint, along with internal components that already clicked and clacked against each other while being pivoted by hand. The original Mercedes axle however, was nearly impossible to move by hand, and no internals could be heard contacting each other what so ever. Several other observations with the aftermarket: the boots were manufactured of substantially thinner rubber, and one of the boots was not installed neatly. In addition the shaft was substantially thicker than the MB unit leading me to believe they have used an inferior steel and need the extra diameter for structural integrity. There were also numerous other areas that lacked the detailing where seals were to seat etc. 

These multiple deficiencies did not build my confidence in the product as a whole and further more I did not want to risk introducing a potentially inferior component into a differential that I know is in immaculate condition. 

On the flip side, no matter which direction you decide to go, installing either axle style is not difficult, but requires more work to change out the homokinetic / aftermarket style should the time come again. As stated previously, the annular is very straight forward after the MB flange is fitted.

Coming Up:  Step-by-Step removal and installation of the rear axles.