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Front Wheel Bearing Replacement
 
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Pelican Technical Article:

Front Wheel Bearing Replacement

Steve Vernon

Time:

4 hours4 hrs

Tab:

$15 to $60

Talent:

****

Tools:

19mm, 13mm (2) sockets, drift or large socket set, large vice grips, floor jack, jack stands, wheel chocks, safety glasses, lug wrench, torque wrench

Applicable Models:

Porsche 944 Turbo (1986-89)

Parts Required:

Bearings, grease seals, high temp grease

Hot Tip:

Be careful when driving the old race out

Performance Gain:

Restore a tight feeling to the front end of your car

Complementary Modification:

Replace brake pads and discs

If you are starting to hear a low rumbling sound from your front end or your 944 has over a 100,000 miles on it you should inspect your front wheel bearings for replacement. The bearings support the full weight of the car both while stationary and under load. As the mileage increases on the car, heat and lack of lubrication can cause the bearings to wear and possibly fail. Replacing the bearings isn't a difficult procedure, but it does involve a commitment to the job as you will be destroying some old parts in removal and will not be able to use the car until the new ones are installed. Make sure you have everything you need before you start.

Before you begin the job place the new races in the freezer, preferably over night if you can. Freezing the races will decrease the outer diameter of the races and make installation into the hub easier.

First thing you need to do is get the car up on jack stands and remove the front wheels removed as well as remove the brake pads. Please refer to our articles on these procedures for more information. If you are going to be installing new rotors while performing this job leave the old ones on while working. The old rotors will provide a wider base or more stable platform while working on the hubs.

With the brake pads removed you will need to remove the caliper from the rotor by removing the two 19mm mounting bolts (red arrows) that connect it to the spindle.
Figure 1

With the brake pads removed you will need to remove the caliper from the rotor by removing the two 19mm mounting bolts (red arrows) that connect it to the spindle. Once the bolts are removed, use care as the caliper will be free to fall.

Remove the caliper from the spindle and rotor.
Figure 2

Remove the caliper from the spindle and rotor.

Make sure to hang the caliper safely up out of the way (red arrow).
Figure 3

Make sure to hang the caliper safely up out of the way (red arrow). Never let the caliper hang by the brake line.

You will need to remove the dust cap.
Figure 4

You will need to remove the dust cap. Use a large flathead screwdriver and hammer and gentle tap the cap forward and off (red arrow). Turn the rotor and tap at several places on the cap to keep it from binding.

With the cap off you will want to clean all the extra grease off of the end of the spindle so you can get at the locking collar.
Figure 5

With the cap off you will want to clean all the extra grease off of the end of the spindle so you can get at the locking collar. Rotate the hub until the opening to the locking collar is in line with the collar. Use a 6mm Allen and loosen the locking collar (red arrow).

With the locking collar lose you can spin it off the threads on the spindle (red arrow).
Figure 6

With the locking collar lose you can spin it off the threads on the spindle (red arrow). There is a slotted washer behind the locking collar (yellow arrow) that sits in a groove in the spindle (green arrow).

You are going to pull the rotor and hub straight off of the spindle.
Figure 7

You are going to pull the rotor and hub straight off of the spindle. When you pull the hub and rotor off the spindle (yellow arrow) together the front bearing will fall out (red arrow), so be prepared and do not let it fall or get dirty.

The outer tapered bearing sits inside a race that is pressed into the hub.
Figure 8

The outer tapered bearing sits inside a race that is pressed into the hub. Check the races and bearings for any scratches, grooves, discoloration or scorching. These are signs that the bearing is worn and requires replacement (yellow arrow). The rollers should also be tight not loose.

Clean all the grease off the spindle (red arrow) and check it for wear as well.
Figure 9

Clean all the grease off the spindle (red arrow) and check it for wear as well. If the spindle shows any grooves or pitting, you'll want to replace it.

With the wheel hub removed from the car, turn it over to the back side.
Figure 10

With the wheel hub removed from the car, turn it over to the back side. You'll see an oil seal pressed inside (yellow arrow). You'll first need to remove this seal to remove the inner bearing and race. Use a seal puller to remove the old oil seal from the wheel hub. If you don't have a seal puller you can use a large flathead screwdriver and something to give you leverage (red arrow). It will take a fair amount of force to pry the old seal from the hub so don't be afraid if the old seal deforms or bends as you pull it out. These are designed as one-time use items. You will more than likely destroy it as comes out.

Now you will have to remove the races that remain inside the wheel hub.
Figure 11

Now you will have to remove the races that remain inside the wheel hub. To remove the outer bearing race, you will need to use something that sits flush to the race; I found a part of a Mercedes bearing removal kit that fit perfectly (yellow arrow).

You want to apply an even force to all sides of the race when removing.
Figure 12

You want to apply an even force to all sides of the race when removing. You can use a hammer to drive it out but I prefer to use a press. If you have a press it is best to use it, as this will keep even pressure side to side when removing or install the races.

For the larger race on the opposite side, you'll have to use a smaller socket or large punch and hit the edge of the race at an angle.
Figure 13

For the larger race on the opposite side, you'll have to use a smaller socket or large punch and hit the edge of the race at an angle. It helps to hit the race around the diameter of the edge to drive it out evenly (red arrow). You will not be able to get a large enough socket inside the hub to apply even pressure during removal so take your time and constantly rotate the hub to remove the race as evenly as possible. Patience is a virtue here, as you need to make sure you do not to damage or scratch the inside bore of the wheel hub.

Take the new inner bearing race from the freezer and place it in the bore on the rear of the hub (red arrow).
Figure 14

Take the new inner bearing race from the freezer and place it in the bore on the rear of the hub (red arrow). Porsche makes an expensive tool to seat the race but you should be able to find a socket large enough to use to press the race in. I found an old ball socket that fit perfectly. You'll want to position the tapered section to accept the bearing. Now press the bearing race into the hub until it seats against the bottom flange of the hub. If you are having to do this with a hammer take your time and make sure that the race goes in straight. It's very easy to cock the race in the bore. Install the outer race in the same manner.

Before installing the bearings into the wheel hub, it's necessary to pack them with grease.
Figure 15

Before installing the bearings into the wheel hub, it's necessary to pack them with grease. The idea here is to fill all the open spaces of the needle bearings. There are a couple different ways of doing this. You can buy a wheel-bearing packer, which uses pressure to push the grease in from the open ends. Or if you are doing it by hand push grease in through the openings on the ends (red arrow) until grease comes out the other end. Then rotate the bearing back and forth.

I highly recommend getting a bearing packer.
Figure 16

I highly recommend getting a bearing packer. Pelican Parts sells a few different ones; they are cheap, very effective at packing the bearings with grease and make what might be one of the messiest jobs in all of motorsports clean and easy.

Be sure to also put a coat of grease on the face of the bearing race (yellow arrow).
Figure 17

Be sure to also put a coat of grease on the face of the bearing race (yellow arrow). Once the bearing is packed, drop it in place on the hub. It's not a bad idea to hold the inner part of the needle bearing and then turn the hub to distribute more grease thru the bearing.

Clean any grease that may be on the inner races of the bearings (red arrow), as you want the bearings to spin in the races not the races to spin on the spindles.
Figure 18

Clean any grease that may be on the inner races of the bearings (red arrow), as you want the bearings to spin in the races not the races to spin on the spindles.

Clean up any grease that may have gotten on the outer surface of the hub where the oil seal fits and center the seal in the bore.
Figure 19

Clean up any grease that may have gotten on the outer surface of the hub where the oil seal fits and center the seal in the bore. Carefully tap the oil seal into place taking care that the seal does not get cocked in the bore on the wheel hub (red arrow). Keep tapping the seal until it bottoms out in the bore.

Now fit the wheel hub back over the spindle and push it back until the seal pops over the flange on the back of the spindle.
Figure 20

Now fit the wheel hub back over the spindle and push it back until the seal pops over the flange on the back of the spindle. Install the freshly packed outer bearing keeping in mind that the tapered section of the bearing fits into the race facing inward (red arrow).

You'll now need to adjust the wheel bearing.
Figure 21

You'll now need to adjust the wheel bearing. While rotating the disc and bearing hub, tighten the locking nut in small increments until the thrust washer (yellow arrow) can barely be moved back and forth with the light push of the tip of a screwdriver. Then tighten the 6mm bolt on the end of the nut to spec. The last step is to put a little of the high temp grease on the inside of the dust cap and place it back onto the hub. Use a hammer to lightly tap the hub back into place.


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Comments and Suggestions:
Tom Comments: I don't like the idea of using a press for race installation or removal in an aluminum hub due to the chance of the race galling the hub.

See:

http://www.924board.org/viewtopic.php?t=35149

for a description of how to do this without resorting to a press.

Your description here is how bearing races are replaced in iron hubs. The techniques differ based on the materials due to the differences in thermal expansion and surface hardness between the two hub materials.
June 10, 2015
  Followup from the Pelican Staff: This method works well too. Thank you for the additional input. I have done quite a few 911 and 944 hubs, and as long as you are not in a hurry the process is safe, and simple and waiting 30 mins for the oven is not necessary. I work in Southern California though where conditions are ideal for the tech, in other climates, other issues may arise and this oven method may become necessary. - Casey at Pelican Parts  

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