Porsche Cayenne (955) Front Wheel Bearing Replacement January 17 2017, 10 Comments
Our Porsche Cayenne 955 parts and people hauler started to have a whirring sound coming from the front axle that was speed dependent. It was time to remove and replace the front wheel bearings. The ease at which this job can be performed is highly dependent on having the right tools. The ball joints, bearings, circlips, etc. are quite large, and you will likely have a very difficult time if you try to improvise a tool or technique. This job is not recommended for beginners, and therefore this DIY assumes that the reader knows how to safely support the vehicle in the air and safely operate a shop press. There are tools that allow the wheel bearings to be changed with the wheel carrier on the car, but we choose to use a shop press instead because high forces are required, removal of the wheel carrier is not overly difficult, and we prefer to work on the workbench than at the axle. We will show you how to remove and replace the front left-hand side bearing, and the right-hand side is the same.
We have to loosen the axle nut, but the process is a bit complicated.
Disable the ride height regulation so that air suspension doesn't fight you or drop the car on you when you lift the vehicle. With the power on, hold this switch in the forward position for approximately 5 seconds until it beeps and the dash tells you that the regulation has been switched off.
Jack the car up and remove the wheel so that you can remove the center cap. A few taps from the handle of a mallet pushed it right out.
Now, put the wheel back on, tighten the lug nuts, and put the car back on the ground. Have an assistant press hard on the brake pedal to lock the wheels from turning. This is so that the brakes and tires react the huge torque you are about to put on the axle instead of the half shafts.You will need a 12-point, 32 mm socket. Our 1/2 inch drive socket and breaker bar was not strong enough to break the nut loose. We had to order a 3/4 inch drive socket to use with our largest breaker bar. Having the ideal tool makes all the difference. Loosen the nut several turns, but do not remove the axle nut.
Now, get the Cayenne safely supported in the air and remove the wheel. We are going to strip everything off the wheel carrier, so that we can get it to a shop press and press out the bearings. We will start by removing the electrical connections. Disconnect the brake wear sensor by prying out gently on the release tab and by pulling down on the connector.
This is the view looking down on the wheel speed sensor. Disconnect the wheel speed sensor by gently prying up on the release tab and pulling the connector off the sensor.
Loosen the nut on the upper ball joint, and unscrew it until it covers the end of the threads on the ball joint. We want to protect the ends of the threads, because when the ball joint pops loose, it can be violent. Not completely removing the nut also helps to keep the upper control arm from flailing when the ball joint pops loose. Place a large Pitman Arm puller on the ball joint and tighten it down. After tightening, tap upwards lightly on the control arm with a hammer to help loosen the joint. Tighten again and tap again as necessary.
This is the Pitman Arm puller that we used (part number 25262). We don't recommend pickle forks because of the high likelihood of damaging the rubber boot. Our smaller Pitman Arm puller wasn't big enough to fit. We broke a 3-jaw puller trying to improvise, before buying this puller from a local Autozone. This job is difficult without the right tools.
Once the upper ball joint is loose, fully remove the nut, and detach the wheel carrier from the ball joint. This will allow us access to the inboard side of the wheel carrier to detach the wiring harness. Unscrew the 2 Torx fasteners holding the brackets onto the wheel carrier. There wasn't enough room for a good photo of the fasteners, but they are near my index finger and pinky. Once the brackets are released, there should be enough slack in the brake lines to detach and reposition the brake caliper.
Remove the 2 bolts holding the brake caliper onto the wheel carrier. Spread the brake pads by wiggling the brake caliper slowly, but firmly.
Secure the brake caliper out of the way by suspending it from the upper control arm. Note the hard brake line coming out of the caliper and try not to bend it.
Remove the brake disc by removing the attachment screw. It is a Torx T-50 screw, and the screwdriver is just for pointing purposes. If there is rust between the brake disc and the hub, it may take a few whacks from a rubber mallet to release the brake disc.
Remove the brake dust shield by removing the shown bolts.
Remove the axle nut, and the 2 lower ball joints. Use the same Pitman Arm puller and the same technique as before on both of the lower joints.
This is the other lower ball joint. Loosen, but don't fully detach this joint. We still need it to support the wheel carrier while we pound out the axle.
If you are trying to remove the nut and the ball joint starts spinning freely, use a torx socket to hold the ball joint from spinning while using a wrench to turn the nut. You may need to use this technique on reinstallation as well.
Pull the top of the wheel carrier outboard and drive the axle into the hub with a punch and hammer. It helps to have an assistant, but is not 100% necessary. Just make sure there is slack in the axle such that there is room for the axle to move inboard. Light corrosion on our axle made it stubborn and required about a minute of moderate hammering.
The wheel carrier should be free now. Remove the wheel speed sensor by removing the hex cap socket and gently prying up on the sensor with a flathead screwdriver. It is plastic, so be gentle.
We now move on the bearing-pressing portion of the job. We had some light corrosion, making the job slightly harder. Judging by how much force our 20-ton shop press had to dish out, it would have been difficult to perform this job with a screw-type bearing press. The first step is to press out the hub from the bearing. The view above is the inboard side of the wheel carrier, and the inner-most part is the hub. Refer to later photos to see how the entire hub looks like.
Our 36 mm socket was just slightly smaller in diameter than the hub, making it a great pressing tool. Other 36 mm socket outer diameters may differ, as the wall thickness of sockets is different from brand to brand. Not having an appropriate diameter socket or other cylinder will make your life difficult. It helps to have a large collection of large sockets and tube segments.
This is the hub about to be pressed out of the wheel carrier. We are pressing it so that the hub exits the outboard side. Though it is hard to see in this photo, there is a gap between the bottom of the hub and the press bed. It took quite a bit of force to break the hub free, as there was some light corrosion.
We spaced up the wheel carrier with some rectangular tubing after the initial breaking loose of the hub. This allowed us to press the hub out all the way.
This is a view of the outboard side of the wheel carrier, and the hub removed. The hub usually takes part of the inner bearing with it, and we will need to remove the inner bearing sleeve from the hub, so we can reuse the hub later.
A bearing separator can get a good hold on the bearing.
Flipping the hub over, we put the lug bolts in the hub, snug them up and then move from bolt to bolt in a circular pattern, tightening each bolt 1/3 of a turn at a time. It will click and pop as the bearing moves off the hub.
The lug bolts will bottom out on the hub before the bearing is slid off all the way. Back the bolts off and then shim the gap with scrap metal and repeat. This method takes a long time, but it works.
A faster method is to use a 3-jaw puller, once a large enough gap has been created to get the jaws under.
This is the inner bearing removed from the hub.
To remove the rest of the wheel bearing, we have to remove the snap ring. Flip the wheel carrier so the outboard side is up. You will need a pair of large, heavy-duty snap ring pliers or angled needle nose pliers. We had to grind the tips of our needle nose pliers to fit into the snap ring holes. Not having the right tool here will make your life very difficult.
This is a view of the inboard side of the wheel carrier. The screwdriver is on the surface of the wheel bearing to show you where to press. We will press out the wheel bearing out the outboard side.
Here we have placed a cylinder of appropriate diameter on the wheel bearing and are pushing the wheel bearing out. This cylinder is from a Harbor Freight wheel bearing kit.
Now the wheel carrier is completely empty. There was some light corrosion which we cleaned up with a stainless steel wire brush.
To aid assembly, prevent future corrosion, and ease future removal, we applied some high pressure grease to the inside of the wheel carrier. A light coat is sufficient.
The new bearing is ready to be installed. IMPORTANT: One side of the bearing is magnetic and will need to go on the inboard side where the wheel speed sensor is. If you get this wrong, the wheel speed sensor will not read anything, and it will likely confuse the ABS and traction control systems. Do not use another magnetic object to test which side is magnetic. You can damage the magnetism of the wheel bearing. A paper clip or small piece of steel is acceptable to use. Screwdrivers are not recommended because some are magnetic.
This is the stack-up that we used, from left to right. Note the size of the cylinder on top of the shiny wheel bearing. It is just slightly smaller than the wheel bearing. IMPORTANT: The inner and outer halves of the wheel bearing can separate under force, as we saw during the removal process. Therefore, to keep the bearing intact, we cannot create loads across the inner and outer portions. So when pressing the bearing in, friction from the wheel carrier is acting on the outer race, so the force to drive the bearing in should only be put on the outer race.
With the new bearing pressed in, install a new snap ring to retain the wheel bearing.
We now need to press the hub back in. Since the hub will be pushing on the inner race, only the bearing inner race should be supported. We repurposed the inner race from the old bearing to use as a support. A strip of thin aluminum rolled into a cylinder can keep the 2 inner races aligned, since the alignment can't be visually checked with the part in the press. The hub will push the roll of aluminum out as it moves into the inner race.
Cardboard may also work. Remember that it may get crushed, depending on your setup.
Here is the final stack up with the hub being pressed into the bearing. With the wheel carrier reassembled, installation back onto your Cayenne is the reverse of removal. When reinstalling everything, we like to anti-seize all the things - all the fasteners and ball joint threads and even the mating surface of the brake disc to the hub. It will make disassembly much easier in the future. The axle nut torque spec is 340 ft/lbs.
The job is fairly straight forward, but there are a few places where progress can be stymied if parts are stubborn and the right tools are not on hand. It took us about 5 hours each side, setting up our tools, working leisurely, taking photos and cleaning up.
Congratulations on replacing your front wheel bearings. Now, go out for a drive to verify that everything was installed correctly, and no ABS or traction control warnings come on.