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Rear CV Axle Shaft Replacement
 
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Pelican Technical Article:

Rear CV Axle Shaft Replacement

Tom Morr

Time:

10 hours10 hrs

Tab:

$200 to $975

Talent:

****

Tools:

Ratchet socket set, combination wrenches, 30mm socket, male M12 triple-square bit, E14 female Torx socket, breaker bar

Applicable Models:

Mercedes-Benz R170 (1998-04)

Parts Required:

Rebuilt axle shaft assembly, replacement hardware

Hot Tip:

Have a spare car to drive in case bolts strip

Performance Gain:

Reliable power transfer

Complementary Modification:

Check rear suspension bushings, replace as necessary

R170 axle shaft replacement can be time-consuming. The at-home time commitment can be significant and quickly become longer if bolts start breaking

This article is limited to axle replacement. Rebuilding the CV joints and replacing their rubber boots is possible, but it requires special tools. The average Mercedes-Benz owner is likely better off sourcing already-rebuilt axles backed by warranties, finding used ones in good condition, or even buying new factory units (202-350-88-10-MBZ).

Stripped bolts are this job's wild card. If the planets align and all fasteners come out without incident, the job is straightforward. However, you can plan on several bolts that hold each axle shaft to the differential to strip and will need tobe cut off. The bolts (001-990-71-12-MBZ) should be replaced regardless.

The only other caveat is that the rear knuckle must be unbolted from the suspension's arms. This allows the axle's outboard, splined end to be removed from the wheel hub. Highlights of the job are shown below.

Begin by jacking up the car and securing it on jack stands.
Figure 1

Begin by jacking up the car and securing it on jack stands. With the tire/wheel off, the 12-point collar nut is visible. Pry its lock-tang loose (red arrow).

Use a 30mm socket on the 12-point collar nut.
Figure 2

Use a 30mm socket on the 12-point collar nut. Apply the emergency brake and use a breaker bar on the socket if necessary to break the nut loose. Always use a new collar nut for re-installation.

Use metric hex/Allen wrenches/bits to remove the cap screws that hold the wheel speed sensor (yellow arrow) and support bracket (purple arrow) to the knuckle.
Figure 3

Use metric hex/Allen wrenches/bits to remove the cap screws that hold the wheel speed sensor (yellow arrow) and support bracket (purple arrow) to the knuckle. (The brakes and backing plate were removed for other articles.)

The suspension's camber strut, torque strut, and tie-rod must be unbolted from the knuckle.
Figure 4

The suspension's camber strut, torque strut, and tie-rod must be unbolted from the knuckle. (Please see the knuckle-removal article for details.) These bolts' heads require a male M12 triple-square (12-point) bit and have either 17mm or 18mm nuts. Then the knuckle can be pivoted downward, freeing the shaft's splined end. Be careful not to overextend the emergency-brake cable.

Spray the six bolts that hold the axle shaft to the differential with penetrating lubricant.
Figure 5

Spray the six bolts that hold the axle shaft to the differential with penetrating lubricant. Tap the E14 Torx socket (yellow arrow) onto the bolt to maximize engagement. Our project car's for-demonstration-purposes-only axle shafts were fine, so we rotated the bolts to the top for best boot clearance prior to attempting removal.

The factory bolts all have thread-locking compound.
Figure 6

The factory bolts all have thread-locking compound. We stripped the heads on four of the six bolts, which is apparently only slightly above average. Subsequently, bolt heads were cut off using a rotary tool (Dremel).

Once the bolts are out or their heads are cut off (yellow arrow), the axle shaft can be lifted out of the car.
Figure 7

Once the bolts are out or their heads are cut off (yellow arrow), the axle shaft can be lifted out of the car.

Removing cut-off bolts can be a work-out.
Figure 8

Removing cut-off bolts can be a work-out. We wedged a large combination wrench between a bolt shank and the car's rear crossmember (red arrow) to keep the connecting flange from rotating. Large vise-grips clamped as tightly as humanly possible eventually work--unless their jaws strip smooth and new vise-grips need to be substituted. Inspect the differential for leaks before installing the new axle shaft.

New axle shafts, bolts, and bolt plates are available from Pelican Parts.
Figure 9

New axle shafts, bolts, and bolt plates are available from Pelican Parts. Installation is the reverse of dis-assembly. Once all components are in place, jack up the suspension until the axle shaft is level before tightening the arms that connect to the knuckle. Finally, check the oil level in the differential.

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Comments and Suggestions:
touring10 Comments: hope you can answer,

why do you oil the axle bolts when installing. the new bolts have loctite already applied. Will this stop the loctite from holding? Also, what torque are the axle bolts.

Thanks in advanced.
March 15, 2016
  Followup from the Pelican Staff: Good catch, you should not apply oil to the fasteners. I will have the article test updated. - Nick at Pelican Parts  
kenji Comments: Looks like it can be slided out. Did you guys tried?
I used a 2 feet pry bar but can't get it to move. Tried to loosen the bolts but they're insanely tight and I don't wanna end up having stripped bolts like you guys.
June 25, 2015
  Followup from the Pelican Staff: On diffs with drive-axle flanges, the flanges can be removed. However, the circlips are strong and have to be release using even force. - Nick at Pelican Parts  
The Great Ike Comments: Do you mean tapping it out with a pry bar or something?
December 9, 2014
  Followup from the Pelican Staff: No, try a oft-faced hammer on the cv joint. You may be able to free it. - Nick at Pelican Parts  
The Great Ike Comments: Hello i have the same problem with my axle shaft but 2 bolts are stripped so i end up cutting the head of both bolts and then i tried to use an air hammer to make a notch in order to grip one stripped bolt out of it's place but that made things worst. Take a look at my picture you can see where i used the air hammer because it looks smashed in but my question was will i be able to pull the axle shaft out by my self since the other bolt was smashed in with the air hammer? Please respond ASAP. Thanks
December 7, 2014
  Followup from the Pelican Staff: I think if the bolt isn't flattened, you should be able to get the shaft off the stub flange now. Have you tried lightly tapping it? - Nick at Pelican Parts  

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