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Schattenbaum Region PCA - Changing 911 Rear Wheel Bearings

 
 
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Fig. 1 Special Tools

 
Fig. 2 Proper Support


Fig.3 Loosening Axle Nut


Fig. 4 Prop Brake


Fig. 5 Rotor Screw


Fig. 6 CV Joint


Fig. 7 Axle Removed


Fig. 8 Hub Puller


Fig. 9 Hub Removed


Fig. 10 Backing Plate Removed


Fig. 11 Removing The Bearing


Fig. 12 Bearing Removed


Fig. 13 Pressing The Bearing


Fig. 14 Center Tool


Fig. 15 Pressing The Hub


Fig. 16 Hub In Place


Fig. 17 Tighten Axle Nut


Fig. 18 Bearing Spreader


Fig. 19 Race Removed

  
Changing 911 Rear Wheel Bearings Minimize

By Branko Kerpan

I am not a mechanic by trade but I love to work on cars. So the instructions below are not meant to replace the factory instructions, they just describe how I did the job. If you have questions or suggestions on how to improve the process please let me know at bkerpan@us.ibm.com

This procedure covers Porsche 911, SC and Carrera,  1974-1989.

  
Changing 911 Rear Wheel Bearings Minimize

When you hear a constant groan from the rear, especially in a turn at speed, and/or if there is play in the rear wheel, chances are you need to replace the rear wheel bearing. On a Carrera the axle nut may back off and you may luck out by re-tightening it. The older  911s and SCs have a cotter pin so if there is play in the wheel, get your hands dirty because the bearing is bad.
To make this job easier and to prevent damaging your car's precious parts, I recommend these special tools shown in  Figure 1. At the top is the slide hammer hub/axle puller. On the left is the bearing separator and on the right is bearing puller/press.

Before you begin make sure that the car is properly supported, Figure 2. Begin by removing the wheel. Put all the lug nuts, bolts nuts and screws in a plastic containers to keep them out of the dirt and to keep them from getting lost. You probably still have a splash shield behind the rotor, not shown here. I took mine off years ago for more brake cooling on the track.

Remove the cotter pin (non Carrera) and the axle nut. On a non Carrera car you'll be OK with 1/2" drive breaker bar and socket (30mm) but on a Carrera you'll need 3/4" drive (and 32mm socket) because of greater torque on the nut. Use a cheater bar on the breaker bar. If the hand brake can't hold the axle from turning use a pry bar or a pipe as shown. Note sleeves on the studs (cut from 1/2" copper pipe) to protect the threads, Figure 3.

Remove the brake pads. Before you remove the caliper, prop a piece of wood between the seat and the brake pedal. You need to push it down just far enough to engage the master cylinder plunger and push it in about 1/2". This will block off the brake fluid feed from the reservoir and keep it from running all over the floor when you disconnect the brake line, Figure 4. 

Remove the brake line. Use 11mm tubing wrench, not an open end or wise grips. Use a 19mm box wrench on the caliper bolts. Cover the brake line hole to keep dirt out and wire brush the caliper bolts before reinstalling.

Remove the two flat head screws that hold the rotor to the hub, Figure 5. If they are rusted on you may need the impact screwdriver (the kind you smack with a hammer). Don't bugger up the phillips slots because then you'll have to drill the screws out. Pull the rotor off the hub. Raise the control arm slightly and support. Remove the shock absorber lower bolt so the outer CV joint can clear the shock as you pull out the axle.

Remove the bolts holding the inner CV joint, Figure 6.  If the axle won't pull out of the hub you may need to tap the end of of it with a hammer and a brass drift to break the rust on the splines. Put a plastic bag over the CV joint to keep out the dirt Figure 7. This is a good time to inspect the rubber boots and to clean and repack the joints if they haven't been done in a while. Make sure that you use a good Molybdenum grease.

The bearing is made up of a single outer race and two inner races. The hub is pressed on to the inner races. You can beat the hub off from inside the control arm with a proper size drift but this puller makes the job a lot easier and you won't damage the hub Figure 8. Notice that I put the lug nuts on backwards so as not to damage the nut tapered surfaces. A few sharp taps with the slide weight will extract the hub.

Figure 9 shows the hub and one of the bearing races. Remove the race from the hub using the bearing spreader, Figure 18 and Figure 19. Next, remove the small cotter pin from the hand brake cable rod and remove the castelated nut with a 10mm wrench. Notice the sequence of the parts; nut, washer, expander, spring, brake shoes and on the other side; expander, washer, spacer tube. Also notice the position of the expanders because if you reinstall them backwards, the emergency brake won't work. Remove the four bolts holding the backing plate with a 13mm socket, Figure 9. You can leave the brake shoes on the plate.

The backing plate hugs the aluminum control arm snugly. On the newer cars it will come right off with a little persuasion, Figure 10. On the older cars the aluminum oxidizes and the backing plate rusts creating an inseparable bond between the two. When I did the other side a few years ago I was pouring Liquid Wrench on it for three days and with all the pulling and banging it would not budge. Finally I had to cut the plate off with tin snips and a chisel. Luckily, my buddy Dan (carsinc1@aol.com) had another one in his vast supply of used parts. Before reinstalling, shine everything up and paint the inside of the backing plate with hi-temp Rustoleum and smear some Never-Seize on the control arm.

Now for the fancy puller, Figure 11. Select the proper size plate put it on the bolt and feed it through the bearing from inside the control arm. The plate should fill the control arm hole completely and be flush against the bearing. Slide on the cup from the outside, followed by the flat plate and screw on the nut. Center the cup by using the bolt holes as guides. Use a socket and breaker bar on the bolt head to keep it from turning and start tightening the nut. If you get a lot of resistance you are not centered. Back off, reposition and try again. The bearing will be pulled into the cup, Figure 12.

----------------------- Installation Process -----------------------
Before installing the new bearing inspect the control arm for nicks, burrs and oxidation. If necessary remove with crocus cloth or steel wool. I put a light coat of WD40 on the surface and wipe with a cloth just before installing the bearing.

Now we will use the puller with it's working parts reversed. Start by sliding the cup on to the bolt first and insert through the control arm from the inside. From the outside slide on the bearing followed by the plate and the nut, Figure 13. The bearing can go either way because it's the same on both sides. Hold everything centered and snug up the nut. It is critical at this point that the bearing is centered in the hole. I use a slide caliper, Figure 14, to measure the distance between the plate and the control arm all the way around then tap the high side and tighten the nut. Continue this process until the bearing is well seated and it will slide in easily the rest of the way.

Install the backing plate, bearing cap and four bolts. Torque the bolts to 34 ft/lbs. Before you install the brake cable, use two 17mm wrenches to loosen the two nuts on the cable at the spacer tube. Back the nuts off so you will get more cable showing through the spacer tube. Install cable and all it's parts in proper sequence. Snug the castelated nut until you can insert the small cotter pin. Tighten the two nuts on the cable to take out the play and continue until the expanders  just start to expand the brake shoes. Now back off  a turn or so and tighten the nuts against each other. Don't forget the splash shield, if your car has one.

To install the hub, use the puller with the same parts and order that you used to remove the bearing, Figure 11 and Figure 12. Use the cup against the hub and not the flat plate as shown in Figure 15. The cup will center itself much better. Hold the bolt with a socket and breaker bar and tighten the nut. This procedure will press the hub into both bearing races.

Slide the axle into the hub and finger tighten the axle nut. Insure that the CV joint gasket is still good (look inside the CV flange) and connect the CV joint to the flange. Torque the bolts according to your application. For Nadella - 34 ft/lbs, Lobro M10 bolts - 60 ft/lbs and Lobro M8 bolts - 31 ft/lbs. From my experience, SCs and Carrera have Lobro M8 (six bolts, 6mm Allen wrench). Hub and axle installed, Figure 16.

Install the shock bolt and torque to 90 ft/lbs. Install the rotor and the two flat head screws. Adjust the brake shoes through the hole in the rotor until they just drag. Install the caliper. Put a drop of blue Locktite on the two bolts and torque to 43 ft/lbs. Connect the brake line and install the brake pads. Remove the stick holding the brake pedal. Finally, tighten the axle nut as shown in Figure 17. Torque the nut to 217-253 ft/lbs for SCs and prior and install a cotter pin that fits snugly. Torque Carrera nut to 333 ft/lbs. Bleed the entire brake system.

Parts and tools: you can get the bearing from Pelican Parts (www.pelicanparts.com) for about $50. The bearing spreader and the hub puller came from Harbor Freight tools (www.harborfreight.com) for about $20 and $50. The bearing puller comes from Performance Products/Automotion (www.performanceproducts.com) for about $150

  
Installation Notes For Brake Caliper Piston With Notched Face Minimize

Some calipers utilize pistons with a notched or recessed surface that presses on the brake pad.  The purpose of the notch is to attempt to even out the pressure applied to the pad, since the leading edge of the pad would otherwise do more work than the trailing edge.  When installing these type of pistons, orient the notched portion such that it faces the leading edge of the pad.  This would generally be facing upward if your caliper mounts on the leading side of the rotor, or facing downward if your caliper mounts on the trailing side of the rotor.  To be more technically correct, there is a Porsche alignment tool to set the orientation, but the above guideline will get you pretty close.

  
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