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Rear Wheel Bearing Replacement
 
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Pelican Technical Article:

Rear Wheel Bearing Replacement

Tom Morr

Time:

7 hours7 hrs

Tab:

$50 to $80

Talent:

****

Tools:

Hammer, drifts, snap-ring pliers, flat head screwdrivers, emery cloth, vise

Applicable Models:

Mercedes-Benz R170 (1998-04)

Parts Required:

Replacement bearing

Hot Tip:

Put the new bearing in the freezer overnight

Performance Gain:

Eliminates the annoying hum

Complementary Modification:

Replace knuckle bushing

If your R170 SLK sounds like you're seated next to the jet engine on an airplane instead of in a Mercedes-Benz driver's seat, your wheel bearings might be bad. Bad bearings can often be verified by jacking up a corner, securing the car, and attempting to wiggle the tire with hands at the 12:00 and 6:00 positions. If any play occurs, repeat the process on the axle's other tire/wheel and compare. Slop that can't be visually attributed to bad suspension bushings indicates a bad wheel bearing.

R170 SLK rear wheel bearings are sealed and non-serviceable, in contrast to many tapered roller bearings. They're pressed into the rear knuckle; extracting them can be challenging. Job-specific tools are available, but these often aren't cost-effective for one-time at-home use.

We removed the knuckle, preparing to take it and the new bearing to a shop as Plan B. Luckily, we were able to use a hammer and various drifts to achieve an at-home bearing replacement--no arbor press necessary. Freezing the new bearing allowed it to be tapped into the knuckle without hydraulic pressure.

The actual bearing swap took a couple hours. The rest of the time is spent pulling the hub out of the knuckle, then unbolting the knuckle from the suspension. Please see the hub, brake, and knuckle articles for removal details.

Replacing the wheel bearing on the car might be possible with specialized tools, but the average SLK owner will probably have to remove the knuckle.
Figure 1

Replacing the wheel bearing on the car might be possible with specialized tools, but the average SLK owner will probably have to remove the knuckle. At some point, the hub needs to be pulled to reveal the wheel bearing. Please see the specific articles on the brakes, hub, and axle shaft for details.

The wheel bearing (red arrow) came unsealed during hub removal.
Figure 2

The wheel bearing (red arrow) came unsealed during hub removal. Unbolting the various suspension arms releases the knuckle (please see that article for details). We had access to an official spring compressor tool (yellow arrow), which we used as back-up so that the shock wouldn't have to contain the spring energy once the knuckle was removed.

The knuckle is relocated to a vise.
Figure 3

The knuckle is relocated to a vise. A large snap ring/circlip (arrow) seats in a groove in the knuckle, retaining the wheel bearing. Normal snap-ring pliers aren't stout enough to remove this clip. We pried it out of the groove (wear eye protection).

We sprayed penetrating lubricant around the bearing race's perimeter, then used a seal drift (arrow) intended for a Dana axle to drive the bearing out of the knuckle.
Figure 4

We sprayed penetrating lubricant around the bearing race's perimeter, then used a seal drift (arrow) intended for a Dana axle to drive the bearing out of the knuckle.

The old wheel bearing (arrow) removes through the outboard side of the knuckle's bore.
Figure 5

The old wheel bearing (arrow) removes through the outboard side of the knuckle's bore. Ball-peen hammer power did the job.

We polished the knuckle's bearing area with emery cloth (arrow).
Figure 6

We polished the knuckle's bearing area with emery cloth (arrow).

Hot tip: put the new bearing (arrow) in the freezer overnight.
Figure 7

Hot tip: put the new bearing (arrow) in the freezer overnight.

Liberally apply high-quality bearing grease to the knuckle's bore.
Figure 8

Liberally apply high-quality bearing grease to the knuckle's bore.

Also apply grease to the bearing's race.
Figure 9

Also apply grease to the bearing's race. We gently tapped it in, using a criss-cross hammer pattern to keep the bearing square in the bore.

We found a drift that was the same diameter as the bearing's metal inner sleeve.
Figure 10

We found a drift that was the same diameter as the bearing's metal inner sleeve. The bearing was gently tapped in until the pitch of the hammering sound changed, indicating that the bearing was fully seated in the knuckle. NOTE: Be aware that this method could possibly damage the new bearing by pushing the inner races out and bending the seals. You may want to consider finding a drift that sits on the outer track of the bearing. 

The new wheel bearing from Pelican Parts includes a replacement snap ring and a new collar nut for the axle shaft.
Figure 11

The new wheel bearing from Pelican Parts includes a replacement snap ring and a new collar nut for the axle shaft. We were able to use large snap ring pliers to compress the ring enough to slot it into the knuckle's retaining groove. Installation is the reverse of removal.

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Comments and Suggestions:
John James Comments: Hi, In figure 10. Is not safer to find a drift that sits on the outer track of the bearing? Thanks
June 18, 2016
  Followup from the Pelican Staff: Yes it is much safer. I will have a note added. - Nick at Pelican Parts  
Wilson Comments: very useful presentation
May 26, 2016
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help. - Nick at Pelican Parts  

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