Help me get rid of this noise!

[ckakoliris]

Hello everyone.
In the last 2 weeks my right rear of the car has developed a loud shake/rattle sound.
I happens when i accelerate above 3k rpm. when thumping the rear right fuchs centre cap with ny fist, it sounds like there is something rattling. could it be lose exhaust manifolds? wheel bearing? I Just had new tires put on...

911 1976 3.0

Thanks in advance.

[tobluforu]

Have you checked the cv bolts? Since new tires were put on, have you checked to see if the lugs are tight?

[ant7]

Originally Posted by ckakoliris

Hello everyone.
In the last 2 weeks my right rear of the car has developed a loud shake/rattle sound.
I happens when i accelerate above 3k rpm. when thumping the rear right fuchs centre cap with ny fist, it sounds like there is something rattling. could it be lose exhaust manifolds? wheel bearing? I Just had new tires put on...

911 1976 3.0

Thanks in advance.

Something inside the tyre ?
Also,Check that the large nut that holds the cv joint through the hub is tight!
Could be just coincidence that the noise has just appeard since tyre change, could also be one of the the rear brake plates rubbing, or the handbrake cable etc.check around the rear hubs and Cv joints etc.
Hope this helps.

Anthony.

[Bob Kontak]

Also check the big muffler straps and all the rhight hand side tubes carrying blown air into the heat exchangers.

[ckakoliris]

Update.
I have checked lug nuts, tight. i jacked the car up and tried to move the wheel. The wheel moved backwards and forwards (radial, not axial). As in it has play when holing the wheel on each side with 2 hands and twisting it, like it would normally rotate.

The brake disk move/twists left and right like it's lose. the bolt that holds everything in doesn't look like it has moved (there's a pin there too) .

Where are the CV bolts? and how much do i tighten them any spec? Muffler straps are tight.

[Bob Kontak]

The brake disc should move the same amount as the wheel. If the wheel is tight, the wheel and brake disc should not move separate from each other.

Tell us more about the brake disc.

The wheel turning sounds normal.

[ckakoliris]

With the wheel off, holing the bolts where the lug nuts go the disk moves. this is with the ebrake on. how do i check/ tighten the cv bolts.

[Bob Kontak]

I will double check if mine moves on my 81 with the e brake on.

CV bolts are on the back side of the wheel entering the hub/bearing assembly. I think there are about eight (could be wrong) allen head bolts that can be tightened down. There are torque specs and methods for tightening but for right now I would get the car high enough and slide under there and hand tighten them pretty snug (with allen wrench) if loose.

You can only do one or two at a time and then you have to rotate the wheel to gain access to the others. CHeck them all - at the trans as well.

Support the car well. We want to hear back from you. ;-)

[Bob Kontak]

Originally Posted by Bob Kontak

I will double check if mine moves on my 81 with the e brake on.

One rear wheel up. Wheel spins freely. With e-brake on the tire at the tread will move less than 3/8 inch and then hard stop either direction. Only that little bit.

[OsoMoore]

In software I frequently do something that may be helpful here. You have one working side and one bad side. Take off both wheels and compare. Does your right wheel/hub do something that the left doesn't? Whatever the difference is, it is probably a bad thing.

[Andy911sc]

It almost sounds like the heat shroud behind the brakes is vibrating. I had a similar issue with my 924 with the heat shroud on the exhaust. When I would be right around 3 grand on the rpms the vibration resonance would be just right for the shroud to make noise.

It sounds like you narrowed it down to a specific side which is good. I would just start at the end of the wheel and work your way into the transmission checking for loose bolts or close tolerances where something could be vibrating together. Since you said it makes the noise when you thump on the center of the wheel, I highly doubt the problem is anywhere else on the rear of the car. The transmission would absorb a lot of the energy from you thumping, so I would only focus on the right rear axle from the transmission out to the wheel.

Also what Osomoore recommends is a really good idea comparing the two sides for reference.

[ckakoliris]

Update
I have just jacked the car up, all the bolts (hex) are tight on both ends. when holding the joint at the transmission end (the whole thing and twisting it, it moves. Is it ment to do that? Additionally then puling and pushing on the cv/ axial rod it makes a lose sound, like a clanking sound. are there bearings in there? or are the teeth of the rod broken? should i open it up? What replacement parts would i need to do this job?

I'll post pics soon.

[ckakoliris]

[wasserkuhl]

OK.

I'd check the following (in this order)

1) Brake calipers and pads secured? Disc not warped, cracked or damaged?
2) Remove wheel and take it to be re balanced, as you mention you have new tyres, its fair to say that possibly the balance weight has dislodged and the wheel may not be in balance.
3) As above, it is also possible that the rear toe/camber settings may be wrong and causing this noise.
4) If all that checks out. Remove the Right rear drive shaft and have the CV's inspected as it may have come apart. Probably best to get them both re furbished while you are there.

I am sure it will be one of these areas. I am more inclined to say its the wheel's balance or your toe/camber settings.

[ckakoliris]

I have found a video that shows exactly what i mean. Mine is the one on the right. I know these are from a 993 although mine makes the same sound. does this mean i have to change the whole axel and cv joints?
Link: Porsche 993 Bad Rear Axle - YouTube

[Bob Kontak]

Originally Posted by ckakoliris

.............although mine makes the same sound. does this mean i have to change the whole axel and cv joints?

At least you found it. Good job.

Yes you need to replace it or the bad parts within the assembly.

If you are looking for a bargain assembly with suspect quality I can find you a link where Vincent Hill bought a cheap axle for a spare. You may get lucky or just get what you paid for, if you know what I mean.

It is a filthy job to disassemble and replace the CV joint(s) themselves. Consider the whole assembly but if your boots are ok and you have only one bad joint, it's do-able in a few hours.

Let us know what you plan to do and we can guide you.

[DohertyCM]

Do it yourself!
The parts are not that expensive....and truth be known, the hard part is getting them out and putting them back in. Get four new boots....don't skimp here go for the quality on these because if they leak, they make a huge mess. Get 4 cv joints....do them all...if one is bad then chances are they all have wear, I will bet they have never been replaced on your vehicle. Inspect your bolts carefully, if they look worn, replace them.
I have never seen the shaft bad, so I would bet that is just fine.

And while the axles are out, clean the areas up real good. This will tell you if you got a leak. I've done them on my Boxster, 911 and 930. They are all the same and are easy to do. Good luck and give us some feedback.

[Bob Kontak]

Originally Posted by DohertyCM

Do it yourself!......They are all the same and are easy to do......

They are doable but a bit frustrating the first time through - at least for me. Mainly, in the cleaning, dis-assembly and re-assembly of joints you wish to keep. Kind of like a puzzle.

You need snap ring pliers.

I am all for it if you are into the DIY experience.

[ckakoliris]

Is it worth changing/ easier to change the whole complete axal or just the cv joints at each side?

[ant7]

Glad you found it!
If you can find a good complete spare shaft and joints then it will save time in getting the car up and running again, you can then rebuild your original shaft at your leasure.

Anthony.