From: Wally Plumley [wplumley@bellsouth.net] Sent: Sunday, December 03, 2000 9:59 PM To: Nick@infinites.com; 928oc@list.928oc.org Subject: Re: [928OC] Rear Noise At 02:14 PM 12/3/00, Nick Tucker wrote: >Now that winter is here, it's time for some maintenance... > >I have a noise in my rear, the cars not mine. > >It's on the right side, a rotaional noise kinda like a bearing noise. It >goes away when cornering to the left, thus putting more force on the right >side of the car. Doesn't matter if I am in gear or not. > >Thoughts are that it is either a bad bearing or a bad CV but I would like >to narrow it down. > >Any thoughts would be appreciated.... Most likely suspect is the rear wheel bearing. First thing to try is tightening the bearing. That puppy torques to 339 ft/lbs, so you need a BIG pull handle! You can torque it by simply removing the center cap from the wheel - no need to jack the car or anything else. I think that it is a 36 mm nut, but I'm not really sure of the size. If torquing doesn't help (and it probably won't, but it is definitely worth a try), you need to have a knowledgeable mechanic check the car. Replacing the rear wheel bearing is not impossible for a home mechanic, but it is not a job for a real novice. Wally Plumley 928 Specialists From: Wally Plumley [wplumley@bellsouth.net] Sent: Friday, October 26, 2001 3:26 PM To: 928 Subject: [928] Rear Wheel Bearings At 06:34 AM 10/26/01, Bill Ball wrote: Besides getting the 322 ft lb axle nut off, what is involved in doing the rear wheel bearings? It appears you have to remove not only the hub but the hub carrier. I gather the bearing is pressed into the hub carrier. Is there any trick to this or do I just take off the hub carrier and take it to a shop to have it pressed out? Step 1 - buy the Factory Shop Manual. Below is a simplified version. First, if your problem is bearing noise, check that the axle nut is tight. The rear wheel bearings are two-row radial thrust ball bearings, and if the nut is loose, you will get bearing noise. The torque on that puppy is 339 foot pounds. That is 80 pounds on a four foot handle! This bearing replacement method worked for me YMMV. Put the new bearing (P/N 999.053.050.02, $82.52 Genuine Porsche, $70.16 OEM, plus shipping) in the freezer. Loosen the axle nut. Remove the half shaft (axle). Remove the caliper - don't take the hose off, just hang it securely on the suspension with a coat hanger wire. Take the brake disk off. Remove the parking brakes, and pull the cable out. On ABS cars, remove the sensor. Remove the upright (hub carrier) by removing one top bolt and partially removing the large bottom bolt. Be certain that you see and understand how the semi-spherical washers fit the hub faces. The shock holds the spring - no compressor needed. Clean everything very well. Drive the hub from the upright, being careful to avoid damaging the hub. This will destroy the wheel bearing. I had to cut the inner race off the hub with a die grinder - the book says to press it off. Don't scar the hub! Clean the hub and put it in the freezer. Remove the parking brake backing plate and the snap ring. Clean the upright and put it in the oven at 300 degrees F (per the shop manual) or at 200 degrees F (worked for me). Carefully (very!) drive the bearing from the upright. Slip the (cold) new bearing in place. Make sure that it goes all the way in - mine just fell in, but I had really chilled the bearing by using dry ice. Reinstall the snap ring, and be sure (very!) to put the parking brake backing plate back on. The bearing should now be pretty warm from the upright heat, and the hub should be pretty cold. Be sure that you have the snap ring and the parking brake backing plate in place, and drive the hub in place, supporting the inner race as you do this. Reinstall everything, being careful to get the parking brake retaining springs hooked over the edge of the holes. Torque the axle nut to 339 ft/lbs. I removed the small center cover from my wheel, and torqued it with the wheel on the ground having someone hold the brakes is probably required. I don't know whether the parking pawl in the transmission would stand that kind of load or not. Good luck! Wally Plumley 928 Specialists From: Wally Plumley [wplumley@bellsouth.net] Sent: Friday, October 26, 2001 6:58 PM To: 928 Subject: [928] RE: Poor Man's 340 ft lbTorque Wrench? At 05:41 PM 10/26/01, Jim Bailey wrote: >I would simply stand with one foot on the end of a 12 inch ratchet , you >might need a longer ratchet . Torque is not too critical as long as it is >enough , it does not load the bearing simply holds the wheel on , nothing >too critical !! I very, very rarely disagree with Jim Bailey - I think most of you know how much I respect his thorough knowledge on the 928 - but I'm afraid that I do have to disagree with him on this one. The axle nut torque is critical. The rear wheel bearings are a two-row, split-race radial thrust bearing, and depend heavily on the proper axle nut torque to achieve the necessary load-carrying capacity. For those of you with manuals, the clearest illustration that I have found is the one on the right side of page 44-32 in Volume IV. This illustration shows the wheel hub pressing on the outside of the split inner race, while the stub axle presses outward on the inside of the split race. The combination of the pressures (achieved by the torque on the axle nut) presses the balls outward into the solid outer race. If the torque is insufficient, the wheel hub and axle stub can move slightly, with the misalignment leading to noise and early failure. If the torque is too high, the bearing can be overloaded, leading to early failure. My suggestion is that you put the axle nuts on at as close to the proper torque as you can. If you leave the center caps off, you can then drive the car to a shop and pay them little or nothing to properly torque the nuts. It should take less than five minutes to do both sides. Wally Plumley 928 Specialists