Dumb question of the day - new axle installation and noise
 

Hey guys,

I've been working on my '81 SC (170K miles) to replace worn rear wheel bearings and CV's. I decided to replace the entire axles, purchased from our host.

Unfortunately I still have some noise from the rear end which sounds a lot like another bad bearing (I was careful when removing/installing the new bearings and used the Arnnworx tool) It's certainly possible that I screwed something up when installing the bearings but they went in fairly easily and all the bolts have been torqued, then re-torqued at ~100 miles.

My dumb question - does it matter which end of the axle is bolted to the inboard vs. outboard side? I assumed that it did since the CV's are the same on either end and have installed them. I can't imagine this causing the noise I'm hearing but just grabbing at straws trying to figure out what to do next.

I didn't replace the Lobro grease (probably should have) I've read that this is pretty lousy stuff but I wouldn't think that it would be so bad that the axles would be noisy. Any ideas?

thanks,
mike

they can go in either way. i just did this same job but i like to buy the cv's and install them on my axles- that way i know whats going in and i can check out the parts before installing them. if you just did both bearings and axles you can probably rule them out, unless you screwed up somewhere. how old are your tires?

Thanks for the reply, my tires are on the way out, probably about 4/32" tread remaining but not shot. When I had them installed I had a good local shop do a 4 wheel alignment and the wear has been pretty even. The tire pressure is right at spec, 34 psi cold.

Wish I knew someone local with a set of wheel and good tires, that would be good to rule out. I do have a brother with an '89 Targa with newer tires, might try to work something out with him but he lives 4 hrs away. Maybe time for a road trip!

The noise is very noticeable from 40-50 mph but nearly silent below that speed. It doesn't seem to vary when the car is side loaded in corners (which would indicate a bearing problem). It also does not seem to be localized to one side of the car but I know it's easy to get fooled.

I'm going to jack it up this weekend and do the 3-6 push/pull on the wheels to see if there's any play. I did re-torque the axle nuts, they were right at 220 ft/lbs.

The 911 chassis transmits noises in weird ways. Couple of things to check:

- Put both rear wheels up and put trans in gear. Spin one wheel to make sure nothing sounds/feels funny with the differential spider gears.

- With trans in neutral, get a friend to help spin both wheels forward/back. Make sure nothing sounds funny with the transmission.

- You should also be able to tell if you've got a rear brake rotor dragging or CV clicking with this.

- Put the rear down and lift the front. Spin each front wheel and make sure nothing's wobbly with front wheel bearings or brake rotors.

The noise at 40, but not at lower speeds as you throw the car from side to side to see if the noise is "sided<" may point to tire noise. I've not heard of a harmonic playing a role in either CV or axle bearing noises - when they get pitted or badly grooved the sounds seem most obvious at fairly low speeds (or cornering).

Were some of the bearings/joints you removed making noise before, so they might have masked tire noise? I agree that if the tires were fairly quiet before the car sat for these repairs, why would they start just now to sing?

Thanks Walt. The right rear bearing was making quite a bit of noise prior to the replacement and when I looked at the race, it was pretty badly worn. It's entirely possible that old bearing noise was masking some tire noise.

I'll get it up in the air this weekend and tug on the wheels and take a closer look at the tires.

Well, I got the car up in the air and found that the left rear wheel has very noticeable play/clunking when tugged from side to side, this would indicate a bad wheel bearing (and a screw up on my part when installing it I guess).

Is there any other reason there'd be play in the wheel/hub?

If I need a new bearing I'll have to hang my head in shame and get a local shop to do it, I'm just too swamped with work and family stuff right now and want it to be right. I did get a quote from a known good p-car shop (Kelly-Moss Motorsports) and was told that the labor was $204. I didn't believe it so they double checked and that's the rate they have listed. Suspect it won't be that cheap...

I'll post the results after I get it done.

It will be interesting to see what they find.
I don't think that a bad rear bearing typically shows up as play. That would be too easy. It shows up as noise.

Play comes about when the axle nut isn't properly torqued, because that is what presses the two bearing inner races together. Or from the bearing not being inserted fully into the banana arm, and then moving some.

But you said you retorqued and nothing moved, so to speak, when you did that. I think in both cases the retorquing would tell you if either happened, but I am less sure about the "not fully inserted" part, because if it really stuck out you couldn't get the cover plate on and flush with that part of the banana arm.

Of course, if you have loose lug nuts you'd have this issue also, but doesn't that only happen to us track junkies at the track? If you recognize the klunk klunk klunk, raise your hand.

Walt, thanks again for the reply. I spoke over the phone with another highly respected local Porsche shop and he recommended tightening the nut to the next cotter pin slot. Not thrilled with this idea but if for some reason the hub and stub axle didn't pull together (due to a bur, etc.) maybe that might explain the play. Not sure how far you can safely tighten the axle nut beyond the torque spec, seems like a bad idea.

Driving in to work this morning I was able to detect noise on the drivers side (loose bearing side) when tossing the car from side to side so maybe that's it.

Regarding the loose lug nut - I've had the wheel off and on several times and made sure to torque t he nuts.

We did the same work - replace rear wheel bearings - and used the Arnworx tool also.
I messed up on one of the bearings and had to remove and replace with another new one from Pelican. So, I bought 2 new ones and now have a spare sitting in my freezer . . . ha ha . . .

It sounds like the KM shop is the way to go for you . . . but, you have mostly succeeded in a very difficult project . . .

Regards,

http://forums.pelicanparts.com/uploa...1468848664.jpg

Roy, thanks for the kind words! If KM does the replacement, it will be the first time I've ever had someone other than myself work on the car. It bugs me to know that I have the tools and knowledge to do it but not the time. Got the "stinky face" from my wife when I casually mentioned that I might have to take another day to work on the car. I figure a couple of hundred bucks isn't too bad to maintain marital bliss :p

One question - when you reinstalled your hub, did you use the Arnnworks tool with the large washer placed on the inboard side of the bearing to support the inner race? This is what I did and wonder if I screwed up somewhere and damaged the bearing. Still scratching my head about the whole thing, wondering where I messed up..

Wow, asking an old guy to remember past yesterday . . . no I don't think I used the Arnnworx tool to press the hub back into the bearing - think I used the CV side and outer hub with the big nut to pull them together, putting pressure on both the inner and outer bearing at the same time . . . I had to go back and look at the photos I took, but don't have one of this . . .

We were doing a coil over spring suspension project on the race car and this bearing replacement was added to make sure we started out with new . . . we recently put the 3.8L in also . . . and Turbo widebody front and rear . . .

Good luck with your project,
Regards,

Thanks Roy, I tried to pull the hub and stub axle together using the nut but could not get them inserted far enough in the bearing to thread the nut on (if that makes sense)

Dropped the car off at Kelly Moss Motorsports this evening so the can replace the bearing, feeling a little uneasy about it. Reminded me of the time I put my kid on the bus for his first day of kindergarten and watched it pull away! Sometimes I think these cars are like pets, you take care of them and they take care of you. Ok, sentimental mode off..