Sounds From the Rear: Explained

I don't believe it does. Would have thought I would have noticed. Going out in it now to see I can determine for sure though.

Ok, I gave it some acceleration and unless it's so slight I'm unable to distinguish it, it doesn't seem to be Crabwalking. I've managed to get a clip of the sound too, in which way is it best to share on bimmerfest?

Sound to me like a loose heat shield or something like that. Since you just had someone messing with the exhaust I would check the insulation under the car. If it is not secure it could make a rattle until there is enough pressure (speed) to hold it in place. Guessing but I would start with that.

Here is a picture I found searching the web:


I think the piece on the right is loose.

does anyone have rear wheel bearing DIY videos?

Yes, just go back a page or two, else search 'Edz Garage' on youtube.

THis job is a SERIOUS pain in the ass though.

Update:

Ok so I've recorded the sound - how would I share this iPhone sound clip with you all?

The sound is there when accelerating but when the clutch is in, the sound disappears.

Cheers Jay Mac for the comment - the pic doesn't display tho? Can you post it again?

scrap that, it did open lol. so it's the exhaust surround you mean. hmm I'll lift the car

Heres clips of the sound. There are three

http://www.craigheyworth.com/bmw325/

Do you have access to a suitable jack? If so place it on the carrier for the rear dif and jack up the rear wheels. CHOCK THE FRONTS FIRST. Place in neutral and slowly spin the rear tires.
Listen to see if you can determine where the noise is coming from, if you get it at all from the car. I had a rattle that drove me nuts. Previous owner said it was the throw out bearing. So did my mechanic. You can imagine their surprise when we pulled the clutch only to find the pressure plate had snapped off the three tabs holding it in place. Drove it like that for 7500 miles including two track events.

Noise stopping when the clutch is depressed is giving me some trouble. Did you just notice that or is that different than when you first noticed it. I could not get the sound clips to play. What am I missing?

20111130 154315.m4a - 1.26MB

20111130 154413.m4a - 0.95MB

20111130 154208.m4a - 1.23MB

Oh, that's strange. Hopefully the links above will work for the clips of the very frustrating 'noise'.

Thanks for your reply.

Ok, so, it's always been the case that with a depressed clutch, the noise disappears. It's the same when coasting. When the noise starts, by playing around with the speed, staying at constant speed or accelerating hard, I can get the sound to disappear as well. Reving stationary never starts or aggravates the noise.

do the sound clips open?

I am getting confused, help me out with these:
You had the sound before your cats were replaced? Yes/ No

The sound comes and goes while driving? Yes /No

When the sound is present, depressing the clutch eliminates it? Yes/No

Is the sound always present now (every time you drive your car) or still intermittent? Yes/No

My thoughts:
Coasting or not the shaft is rotating so it must have something to do with being under load. It still could be any of the things that have been described. I don't know what happens to the shaft under load but it would seem to make sense that it should move do to torque and the load placed on it. A tapping or clicking noise could be some thing hitting slightly, it could be a part that is worn, similar to a cv joint clicking, indicating binding.

Flex disc
u joints
hitting insulation
drive shaft brace

Check out realoem for the diagrams to see what you should be looking for.

Frustrating as hell but one step at a time. Focus on the fact that to have someone do this for you will cost you $$$ but as always SAFETY FIRST. If you do not feel comfortable don't do it but then you have to bust out the check book.
Good luck!

Hey Jaymac,

Yeah, extreeeeemly frustrating lol. Your right though, one step at a time.

Cheers for the reply

Ok, so to answer your questions:

I didn't have the sound before the cats were replaced.
The sound does come and go while driving
when the sound is present, depressing the clutch always removes the sound
The sound is still intermittent.

I've only got the standard bmw jack so I'm gonna head out this weekend and invest in a heavy duty one. I'll get on realoem to get some diagrams to see what I'm looking at.

I have had good luck with these:
http://www.harborfreight.com/rapid-p...html-7814.html Some car mags have coupons in the back and you can get one for less than $60.
Another idea if you have the access is DOT scales. Most are closed on the weekends and they have pits you can drive over. Can't remember what you have out there. If you need an oil change you could do it there also, or wait until you need one. if you can tolerate it.

As for your answers, I still like the insulation or something that is loose as a result of the work you had done. I have not been able to get the sound yet but I will work on it this weekend.

I have H&R race springs so the car sits a little low. I use pieces of 2 x 10 and place them under the wheels. It is easier than jack stands and cheaper if you have access to the wood. Another option is to see if you can find someone with car ramps and place them behind the rear wheels and back up on to them. That should give you access to the under side of the car. If you are checking for loose stuff keep in mind that you might have a worn part but are unable to generate the force needed to wiggle the item. Start with the simple things first and just keep telling yourself that you are going to find it.

The fact that it comes and goes would make me think it is not a big deal yet but you can't ignore it.

Thanks for the detailed advice JayMac,

The sound has been getting progressively worse over the past weekend so today I had enough and took it to 'another' garage. They drove it, heard the sound and said it sounded like the rear drivers side wheel. He lifted it saw nothing wrong at all and could not replicate the sound. The only suggestion he had was the possibility of the cat con surround been knocked up when I had the cats replaced. I noticed that it wasn't connected properly either. He kinda yanked at it and let the car down saying that he could not determine the cause. However, leaving the yard and all the way home... you guessed.... not a peep, no sound at all!?!? seriously crazy. This happened the last time I took it to a garage but I don't know what they did as I left it with them. I still don't know exactly what the sound is. I just know that both times, after it being raised, it went in with the sound, out without.

Any further ideas?

I managed to get off a couple of quick photos before he lowered it (don't think he was impressed lol)

Looking at the photos theres nothing 'really' evident on them as they aren't the best angle. On the faaar right of the first photo you can see where the screw is missing holding the drive shaft protector in place

Ok, i've now been told that it's definitely two parts that hold and support the drive shaft. cost to repair 800-900 dollars :-/

The center support bearing? Those only cost around $30-40 for the part, and labor is easy.

Which part(s) are we talking about here?

basically, I told the garage the symptoms, the knocking when accelerating, it's intermittent etc etc and he said that there are two parts that need to replaced. He mentioned there's some sort of support for the drive shaft which will need replacing and the circular rubber part in the shaft that surrounds the six bolts or something. (bushing?). Yeah and quoted me 800-900 (prep boys)

hes talking about the guibo and the center support bearing

I believe this part is what he was referring to http://www.carpartsdiscount.com/auto...tml?3593=74584

I see. Is this something that when failed could create knocking when accelerating?

just reading some forums now and apparently I should be able to determine if this is the case by rotating the back wheels with the engine off, something I done a couple of times now with out any knocking or grinding :-/ hmm

you can visually inspect those parts

He's talking about the flex disc (aka: guibo) and the center support bearing, and he's trying to rip you off big time. The flex disc costs about $75, and I just looked up the center support bearing, which actually only costs $19 (these numbers are for OEM parts, too). Like I said before, labor for this job is very easy, and I can't imagine this job taking an experienced mechanic more than an hour or two. So, an estimate of $800-900 is total insanity.

You may need to have these parts replaced, since they are regular wear items, but I'm not convinced they are actually the cause of your troubles because A) when they go bad, the sound usually comes from right underneath the front seats, and B) when they go bad, they make noise all the time, not intermittently.

I recommend getting a second (or third) opinion. And definitely don't take your car to Pep Boys for work...