Sounds From the Rear: Explained

Ok, great advice thanks.
When I got the last garage to lift it, all he did was yank and pull around the metal protective drive shaft surround. The one in one of my above photos and it after driving it in with unavoidable knocking, I drove it out with none.
Ok so under my car I get then. Put it off as I live in a flat in the centre of west hollywood. Difficult to find somewhere I can lift the bleedin thing lol.

oh, and i did notice that the flex disc did have 'some' cracks around the bolts. I thought that where minor so if it isn't the cause of the noise then it probably will need replacing soon so I'll have to keep an eye on it I recon.

haha, ok, I wont lol.

Great Advice! I'll be taking photos of the flex disc and support bearing, see what you guys think. Seriously at the end of my tether with the knocking haha. Can't even have the hood down now as I just draw attention to myself. I'll check out any loose insulation etc

http://www.pelicanparts.com/BMW/tech.../E36-Guibo.htm

Read this and plan accordingly

I had a 320is back in the '80's and it had a sound like someone tapping on a pie tin. I was told heat shields but after three times back to the dealer they found that the shaft brace was broken. Warranty but back three times was a pain in the ass!

Is the sound gone or do you still have it?

perfect, I was looking foe a play by play. Yeah, the sounds still there. Still intermittent and still annoying :-/

Ok, so managed to jack up the car, have a look round and take a load of photos. I didn't have enough room to be able to get behind the exhaust system to check the drive shaft surround, but got some pretty good pics of the flex disc. Have a look and let me know if you can see anything that may possibly be causing the noise. Didn't really do it all day today. Right click photos and open in new tab or window to view

oh, ok they've uploaded this time, massive, apologies

UPDATE:

Took it again today to get another opinion. He lowered the exhaust and removed the headsheild for the driveshaft. The flex disc and drive shaft support mount are in good order. No problems there. After putting it back together, and securing the heat shield tightly, we took it around the block and it made no noise. I started to drive it home, and you guessed it, it made the dreaded mystery knocking sound!!! I took it back and I removed the back seat and kept the widows up so we could establish exactly where the sound was coming from. He thinks it's the rear drivers side wheel and anticipates it may be the axel. Any ideas on what could be making the knocking noise from the rear drivers side wheel?

Have you checked your rtabs?

no i haven't. is there a way to determine if failure of the bushings is the cause of the noise?

the clunk sounds like it is in the rear end of the car

Gets worse and worse

at first youll only hear it while going over a bumpy road at times,

the rear end of the car will feel like it sways over bumps, and it will wear out tires when combined with a lot of negative camber

ok. yeah the sounds is definitely coming from the rear of the car. and more specifically, the rear drivers side. after it's been lifted, and it's making the noise, anywhere between 5 mins and 2 days. It don'ts make the sound when going over bumps, not noticeably anyway. I don't particularly notice the car swaying over bumps or under hard acceleration.

Is there anyway it could be my parking break knocking? Mine is particularly bad.

brake*

Craig, When you get the noise. Will it make the sound if you drive in reverse? I do not know what a cv joint sounds like when it is back but have often heard it referred to as a clicking sound.

I had a shaft go bad on my 328 and needed the whole shaft. Pricey through the dealer but there are aftermarket ones that are not too bad. I had a thumping sound on one of my cars and could not find out what it was. I would run the car up to 40 mph and shut it down and coast. It was coming from the rear wheel. When I found that out I was told it was the nut on the end. When I torqued it down it moved the equivalent to 1 hour on a clock face or about 30 degrees. No more noise.

It could be the shaft. Could be the dif too, you have limited slip correct?

Try the shut down thing. Low speed first just to make sure you get the hang of it so you are not locking your steering. Parking lot at a school on a weekend is a good spot.

If it is the brakes you can look at them yourself. Do you have any tools? If you determine it is coming from the wheel make sure your dust shield is not hitting the rotor. 21 in the diagram.



I think the parking brake is only on one side. Not sure on this maybe someone else can chime in.

Parking brake is on both sides.

Okay, thanks! The other thing you can do is to tap on everything you can that rotates under there and see if you can duplicate the sound. If you can't then it might be internal.

Notice failure symptoms:

Description
A CV Axle is the drive axle on a BMW 323 (E36) that contains two constant velocity joints. CV axle shafts are mainly used in front wheel drive and all wheel drive cars. However, rear wheel drive cars with independent rear suspensions typically use CV rear axle halfshafts. Some all wheel drive vehicles use CV axle shafts for all four axles. Two different types of CV joint are used on CV axles in modern cars. At the "inboard" end, where the shaft only moves up and down with the movement of the suspension, a "Triax" (also known as "Tripod") joint is used. This has a three-pointed yoke attached to the shaft, which has barrel-shaped rollers on the ends. These fit into a cup with three matching grooves, attached to the differential. Since there is only significant movement in one axis, this simple arrangement works well.

At the outboard end of the driveshaft, a slightly different unit is used. The end of the BMW 323 (E36) CV Axle is splined which fits into the outer joint and is typically held in place by a circlip. The shaft fits in the center of a large, steel, star-shaped gear that nests inside a circular cage. The cage is spherical but with ends open, and it typically has six openings around the perimeter. This cage and gear fit into a grooved cup that has a splined and threaded shaft attached to it. Six large steel balls sit inside the cup grooves and fit into the cage openings, nestled in the grooves of the star gear. The outer shaft on the cup then runs through the wheel bearing and is secured by the axle nut

Purpose
The Constant Velocity Joints in a CV axle allow a rotating axle shaft to transmit power through a variable angle, at constant rotational speed, without an appreciable increase in friction or play. The CV joint in the CV axle is extremely flexible, and can accommodate the large changes of angle when the front wheels are turned by the steering system.

Maintenance Tips/Suggestions
The only maintenance required on BMW 323 (E36) CV axle shafts are periodic inspection of the rubber boots that contain the grease to lubricate the CV joint. Check these boots for damage, cracks will allow the grease to leak from the boot and dirt to enter the boot causing damage to the CV axle shaft. It is best practice to replace the complete CV axle shaft if the boot or CV joint fails

Failure symptoms
A clicking noise when turning sharply at low speed is a symptom of a failing CV joint in the CV axle shaft. Cracked and grease leaking from CV boots.

WARNING
Ignoring these symptoms can lead to total CV joint failure rendering the vehicle inoperative.

AKA
Half Shaft, Constant Velocity Axle

Location
On front wheel drive vehicle the CV axle is located between the wheel hub and transaxle or transmission. On vehicles with rear independent suspension the CV axle is located wheel hub and rear differential.

Disclaimer
Depending on the year and options your BMW 323 (E36) has, the above information may not apply. Consult with a professional automotive technician or manufacturer for specifics on your BMW 323
A1 Cardone 60-9197 Axle Assembly

Originally Posted by PhilipWOT

Good write-up, but you forgot one:
It sounds like an airplane engine taking off when I slow down- Worn out LSD. Time for a rebuild or new diff fluid.

i have this same noise, when i hold the clutch in it kinda goes away, so u think its a worn diff? i know my lsd is bit worn had sum play in it

Hey Guys,

Thanks for the awesome detailed responses!

So, I've tried the shut down coast. The sound completely goes. The sound is completely sporadic, with sound half the time and not the other, but it always follow certain rules. The clutch HAS to be engaged, and 90% of the time I have to accelerating. The other 10% it does it when travelling a constant speed or decelerating by taking my foot of the gas. If depress the clutch, or take it out of gear and coast, or turn the engine off and coast, the sound will always disappear. The sound varies constantly in volume, sometimes being quiet, sometimes being reeeeaaally loud and embarrassing.

My hand break (parking break) is virtually useless and I have to have it in gear when on a hill to be certain it'll hold. Read in a few places that this could sometimes cause this type of sound. My mechanic thinks it may be my back drivers side axle, but I'm thinking more along the lines of rtab (rear trailing arm bushing). Only because, when I bought the car a couple of months ago, I drove down the private sale price massively because all 4 tires needed immediately replacing. They all had wear on the inside of the tire, which I assumed was bad alignment and he had been rotating his tires. I've heard that failing bushings cause bad tire wear?

It was due in again to day after taking it in and checking the drive shafts flex disc, support mount and head shield, all of which are in great condition, but he rescheduled for tomorrow. It's in tomorrow at 9 and we're going to look at the drivers side rear.

Still annoying, still a mystery, however I've now found a mechanic who will take me seriously and is willing to work out this mystery with me, and I replaced my broken stereo, so with enough volume, I can live in ignorance lol.

I'll keep you updated.

With regards to the CV joint. I believe I had one of these go on one of my first car. It is a similar sound to that, though not entirely the same. The mainly sounded when turning. This does sound when turning but only if I accelerate through the turn. Constant speed, or no gas removes the noise generally. I believe I attached photos above of the rubber boots that contain the grease (if I've pictured the right thing) and they are in good condition.

Let me know if I'm talking rubbish lol

From you description of the sound, it may be the joint. Accelerating would be a load on it as well as deceleration just from the opposite direction. As for tire wear, BMW's are notorious for being hard on tires. The fronts usually have too much toe which will scrub off tires. It makes the car drive straighter but you pay for it in tire wear. If you plan on keeping the car, new bushings are great. You get a great ride back and all those annoying sounds disappear. Did you have the car aligned when you got the new tires. If so they should have a print out of what you car had for specs. When and if you do get aan alignment, try to find a shop where the tech actually aligns the car not just adjusts crap until he gets the right color light. Check with local speed shops in your area. They may be able to steer you in the right direction. No pun intended

Hey Jay,

I never had the car alignment done after replacing the tires (fail) but plan on after solving this sound.

Ok, so I've just got back from yet the garage. Previously he lifted the car and established that it definitely wasn't the drive shaft support mount or flex disc. Today we had a look at the rear drivers side (us) tire. He lifted the car and I drove it. It produced no knocking noise when in the air. We had an external look at the axle and bushing. He never lowered it to see the bushing or removed anything to get a better look at the axle. He guessed that it would be the axle, quoted me 300 dollars for a refurb axle and said that if it didn't solve the problem that he wouldn't be liable. Didn't want to take the gamble so walked, and came back the trusty forum guys that are here on bimmerfest!!

An addition to all the symptoms and info above throughout all the posts now, I believe I know why it is often sporadic, and I have that elation of 'yeah, it's sorted' after taking it to a garage. It's weight related. When the pressure is off the drivers side for a while and then driven after, it no longer knocks. Anywhere from 10 mins of driving to 2 days of knock free driving bliss!!

Anyone know if the axle would respond this way, or the bushing?

I still think its the RTABs.

I had my RTAB's replace as part of installing the Turner kit. Don't know what worn ones would feel like just did it as a part of a project when Installing the LSD. If it were the RTAB what would cause the tapping noise? Not arguing with your thinking rather trying to walk this through. If the bushing was worn there should be deflection when acceleration and deceleration, but the taping would/should not be in the bushing because there should be a load on it. If it is the RTAB and it is worn to the point of deflection the movement of the trailing arm may allow a contact point somewhere and you have to find it. If you noise is metal on metal there is going to be some wear somewhere. Find it and you are on your way. Did you have the tire off when it was in the air?

The truth is we have older cars so stuff is going to wear out. That means what you save in price upon purchase you may have to spend after. The benefit is that you know what and when work was done. You can buy those axles from Parts Geek for $50:http://frugalmechanic.com/auto-part/...ardone+60-9197

Here is some diagnostics for the RTAB:


The rear trailing arm bushings (RTAB) of the E36 is a common wear item on all E36/E46 coupe/sedans (not Z3s or Ti). During acceleration and braking, the dynamics of the rear suspension settings change (by design). Specifically, the rear wheels get positive and negative toe, based on what the car is dong (squatting under acceleration or lifting under braking).

As the bushings wear, the vehicle will begin to wander. A test (on an open stretch of flat, straight road) can be done easily to verify and confirm if the bushings are worn. While traveling in a straight line, at moderate speeds (40mph), firming press the brake pedal WITHOUT HOLDING the steering wheel. If the car begins to veer to one side, this may be an indication that one (or both) of the bushings are worn. Another verification, while traveling at the same moderate speed (40mph), STOMP on the accelerator (2nd or 3rd gear). If the car lurches to one side, this may also be an indication that one or both of the RTAB are worn.

For all E36s produced to 1995 (including the M3), they used BMW # 33 32 1 097 009. A common upgrade is using the rear trailing arm bushing from the 96-99 M3 (US and Euro) BMW # 33 32 2 228 153. If you plan on using these factory replacements, you may want to consider purchasing Trailing Arm Bushing Limiter Kit while you're doing this job.

See if you can get what they are talking about here. If you posted I forgot. What is you mileage on the car?

Originally Posted by cyris-skrila

helloo guys i accidently drove my lowered car over a curb nad therefore noticed a rattling noise whilst driving!help plzz

My newest favourite!

teheheh.
every once in a while I've got to troll a newb.