Wheel Bearing Help

[n8marx]

I need some help.

I have what I think is a bad wheel bearing on the left rear of my car but I'm want to be sure before I go tearing into it. A little background. I bought my car in July of this year. At the time it made a slight groaning noise from the rear only when turning left. Now, 5,000 miles later, it makes the loud groaning noise all the time. Sounds like a freight train is tailgating me at speeds above 20mph. The noise is independent of engine speed. Coasting in neutral or with the clutch in produces the same noise. A couple of threads yesterday suggested it might be my worn RE730s making road noise. No dice. Changed to my track tires and the noise is still there.

Here's the rub. Nothing gets hot like a bad bearing should. Also, with the rear of the car jacked up I tried to shake the wheel. No play in the bearing. I then rotated it by hand. No wierd noises. On both sides of the car I could hear the bearing rotating but nothing that sounded bad. The fronts were dead quiet. Should the rears sound "dead quiet" like the fronts or are both rear bearings bad since they both made some(minimal) noise? Is there something else back there that could be making a loud groaning noise(ie. differential, gear set, etc.)?

Help!! Winter is fast approaching here and I'd like to get this diagnosed before the salt flies so I can fix it this winter.

[Tim L]

OK, I just had a bearing go bad in the back. If you rotate the rear wheel it should be dead smooth if it feels the slightest bit rough its bad. BTW my bad bearing had no play at all.

Tim

[88911coupe]

I was hearing some similar sounds on my '87 cab and it turned out to be a problem with one of the emergency brakes. Much easier to repair/replace than the bearings. May be worth checking into before you take the bearing out which is a lot more trouble than the fronts.
Good Luck,

[Superman]

True. It should be dead smooth. It's not easy to identify which wheel bearing is bad, but the symptoms you report are absolutely conclusive. You do have a bad wheel bearing. Perhaps even both the rears.

If you're going to try replacing them yourself, you will need the tool. It's theoretically possible to replace them without the special tool, but it's not a smart idea to try. And finally, just be sure to put sufficient torque on the big nut. Spec is astronomical, and the important thing is not not put it on looser than spec.

[john walker's workshop]

there's so much axle and transmission drag that it's hard to spin the wheel fast enough to hear much. bad rear bearings rarely have discernable freeplay in the wheel unless they're really toast. if there's a slight bearing noise when it's spun by hand, it's probably bad. once the axle, caliper and disc are off, spinning the hub is much easier and then you will really hear the rumble. load each bearing in a sweeping turn to see if it aggrevates the noise. left turns load the RR bearing for instance.

[n8marx]

I don't recall "feeling" anything when I was rotating the rear wheels. Just "heard" a slight bearing noise. Will try again tonight and pay special attention to the "feel" of the bearing.

About this special tool. Is it just a bearing puller or is it a "Porsche specific" bearing puller?

[Superman]

It is not Porsche specific, but it does have to fit. I'm sure Pelican can hook you up. It'll cost perhaps $200 if you don't know someone who has it already. Generic sets probably will have the right sizes. The tool is a big steel cup, and big thick washer and a big bolt and nut. The bolt and nut push the bearing into the cup using the thick washer. When I say thick, I mean thick.

[n8marx]

Thanks for the info, JWW. I guess next step is to start disassembling to investigate further. Calipers and axles coming off soon. Driving season aborted due to mechanical difficulties.

[stormcrow]

Before you go tearing in to it, I would do a temp check on it. If the bearing is bad, the hub will be a lot hotter on one side then the other. Take a temp reading on both sides after you've had it out on the road for a short run. This is a good way to make certain it is the bearing and not something else.

Steve

[n8marx]

I performed some more checks tonight after work. I drove the car and then checked each side to see if one was warm. Nope. Both sides were stone cold. I then jacked up the rear of the car and blocked the front wheels. I rotated each wheel by hand and could not "feel" a bad wheel bearing. I then started the car and slipped it into 5th gear. I let it idle in gear with the rear wheels spinning(sounds bad but I really had it braced well). The noise didn't seem to be coming from either side. It seemed to be coming from the center of the car. For the next check I raised only the left side of the car and again let it idle in 5th. No noise. I then raised the right side of the car and did the same thing. The noise was back.

So, I have narrowed the bad component to the right side of the car, not the wheel bearing. Could a bad inner CV joint make this noise without the usual clunking? Is there a bearing in the transaxle case that might be bad?

[Tyson Schmidt]

No you haven't ruled out a bad wheel bearing. You need to remove the axle, caliper, and rotor to be able to feel the bearing properly. I can't tell you how many times a wheel bearing has felt fine when everything is together, but felt awful once all the ancilliary components were removed. Spinning the whell in the air is not a good method, since most of the time the bearing will only make noise when it is loaded.

[Tim L]

I think it's a bad bearing. When you spin the tire slowly you shouldn't hear any bearing noises or feel the slightest of bearing roughness. The left turn groaning is telling you that the right bearing is going bad, I wouldn't rule out the bearing.

Tim

[n8marx]

Tyson and Tim,

Thanks for bringing me back to earth. I was trying so many different things last night trying to convince myself I didn't have to replace a wheel bearing. I'll have a little more time tonight so I plan to dismantle both sides and investigate correctly.

[Superman]

In my mind there is at least a 99% chance that your right rear wheel bearing is bad. Trust me, I'm a statistician.

[LFogelson]

I have been struggling with a similar problem on my 82 SC from the right rear. I had a metalic cyclic squeek-scratch noise in May that I thought was a rubbing rotor shield. It went away when I straightened it...but the weather was also warmer. By the end of the summer I noticed the right rear wheel wobbled A technician told me my bearing was bad. I went home and tightened the "crown" axle nut and everything was fine for 4 weeks and I thought the technician was a crook (he overcharged for some other work, and tried to sell me some expensive "fixes"). As soon as it got cold the scraping started again and there was no wobble in the wheel. I changed my e-brake drums because the right became weak, still the noise. Brought it to a trusted technician who drove it, put in on the lift in and out of gear. No noise. The noise is only under load, worse when cold, worse when coasting, worse turning left, worst coasting left turn on a cold morning. Technician thinks it is the bearing but said I can wait and it should get worse and more constant (non-cyclic). Further, he suspects that the outer part of the "wide" bearing is bad in one spot and aggravated by shrinking in the cold. I am curious what happens with your car. If I decide to just change the bearing without waiting (really annoying sound) I will let you know.

[Bart911Man]

This summer my '80SC started to develop just that noise. reaches its peak between 35 and 60 mph.
With the targa top off it's ok, but with the top closed it's realy like driving a coffy grinder.
I am planning to take out my gearbox this winter to have it revised. Was planning on changing bearings as part of the project.

I'm realy curious to heare of the outcome of your troubleshooting n8marx!

Goog Luck!
Bart.

[n8marx]

I got everything torn apart to discover that it was in fact a bad wheel bearing. Without the brakes and the axle in place rotating the hub feels as if there are detents in my bearing. Not good. John Walker, Tyson and Superman were right on the money.

Now the question. How in the world do you get the hub out of the bearing? A search of the archives told me that you pound it out of the inner bearing race from the back side. So far no amount of slide-hammering will budge it. Is there a trick to this madness?

With a little luck I'll get to drive again before the salt flies.

[Neilk]

n8marx,

Good luck! Jordi, a fellow Pelicanhead, had a pair of aluminum trailing arms with hubs for sale at our local swap meet. I took a look at them since I am contemplating changing the rear bearings as well. Getting the bearing with hand tools seems really difficult. I am looking forward to hearing about your repair.

[john walker's workshop]

there are no special tools currently available to pull the hub out of the bearing on a 911, even though the manufacturer of the vw and honda tool says it will. i use a pair of 3 foot long prybars, (they look like giant screwdrivers with angled tips) inserted on each side of the hub, with their tips against the retainer plate bolt heads, which are directly under the flange. then take up the slack and give a good hard pull, or two, or three. be careful if the car is up on jackstands, as it can easily fall sideways and cause personal injury. then R+R the bearing. then pull the hub into the new bearing with the special tool, which is just a big all-thread with thick washers. be sure to place the thick washer (1/2" thick) behind the inner race as the bearing is pulled in, or the race will be pushed out and the bearing will be damaged.

[beepbeep]

Talking about bearing, this is what mine looked like:

I overtorqued bearing to fix "bearing play" (due to worn bearing) which consequently cracked outer bearing race together with banana-arm.

3600$ of damage...

One of those expensive DIY-lessons