Noise near side rear

[Pinky white]

Today we drove back from woodstock to the Isle of Wight
Car went well,
However when doing 80 miles an hour and coming of the throttle
I can here a wine, going back on the throttle it stops, not that noisy
yet but you can tell it is going to get worse

Car is a 2.8 49,000 on the clock

I think it could be the drive shaft ?

What do you think

Cheers pink

[Del]

I've heard of similar when diff oil is low. I would change the diff oil (or at the very least check if topping-up is required) & visually check for leaks. Then see if the situation improves. One can overly focus on the low 49,000 miles and possibly forget that whatever is in the diff, is 12+ years old.

If your car has a limited slip diff, you require fully synthetic gear oil (GL5 rating) 75W-140.

http://www.zroadster.net/forum/viewtopi ... 18&t=17948

[Pinky white]

I've heard of similar when diff oil is low. I would change the diff oil (or at the very least check if topping-up is required) & visually check for leaks. Then see if the situation improves. One can overly focus on the low 49,000 miles and possibly forget that whatever is in the diff, is 12+ years old.

If your car has a limited slip diff, you require fully synthetic gear oil (GL5 rating) 75W-140.

http://www.zroadster.net/forum/viewtopi ... 18&t=17948

Thanks fir the reply
I don't no if it has a limited slip diff the year is x reg 2000
Thanks pink

[peter2b]

double check swmbo isn't still hanging on the door handle
peter2b

[wonderloaf]

I've had the same thing with my car since I've had it ... got the car with ~22k miles on the clock, now at 82k and still have the same noise, although much reduced now since changing the diff oil. I've looked around the internet quite a bit and there are some stories of people who have had their cars from new and who have their diff's replaced and still no joy, so seeing as mine as didn't get any worse since I bought it I elected to live with it and change the diff oil to see if that helped, which it did.

If you do go to change the oil it's very easy, although I did have to buy an oil suction gun and a diff plug socket to get the job done!

[Del]

I don't no if it has a limited slip diff the year is x reg 2000

If you give your VIN number to any BMW dealer they can supply a print-out of original, optional fittings. A limited slip diff is denoted as :- 'Sperredifferential 25%'

[Southernboy]

I have noticed the "diff whine" is more pronounced after extended high speed driving added to distance. I guess the hotter the diff gets, the more it tends to produce the symptomatic BMW diff whine. It's quite common. I was told by a BMW mechanic that it is amplified by the hollow axle carrier to which the diff is anchored too. He told me that they use an expanding foam to fill the hollow arms of that carrier which apparently minimises the amplification of the diff.

#1. on the diagram below.
The propshaft goes through the large hole in the middle, and the diff is mounted to the rectangular section at the top middle. The two arms which go left and right are hollow and it seems they amplify the diff noise.

[wonderloaf]

I have noticed the "diff whine" is more pronounced after extended high speed driving added to distance. I guess the hotter the diff gets, the more it tends to produce the symptomatic BMW diff whine. It's quite common. I was told by a BMW mechanic that it is amplified by the hollow axle carrier to which the diff is anchored too. He told me that they use an expanding foam to fill the hollow arms of that carrier which apparently minimises the amplification of the diff.

#1. on the diagram below.
The propshaft goes through the large hole in the middle, and the diff is mounted to the rectangular section at the top middle. The two arms which go left and right are hollow and it seems they amplify the diff noise.

Has anybody tried this?

[Southernboy]

The M version cars have the rear carrier filled with metal shot particles to add weight to the rear axle / tyres for added traction. The BMW mechanic noticed that it was the non M drivers who commonly complained about diff whine. Since the only difference in the components at the rear of any consequence was the empty vs filled axle carrier, he gave it a try using the high density expanding poly foam. He told me it worked very well, and that it is now common practice as a treatment for the complaint. I haven't tried it, but common sense tells me that, if the diff which is attached to the carrier emits any noise, an empty tubular metal object will resonate the sound. It's cheap enough to do, and certainly can't do any harm. If anything it will keep water and muck out of the carrier.

[Hairyscreech]

It's a specific type of expanding foam you need, it's now quite common to use it for automotive box sections but you need a closed cell foam, otherwise it will soak up water like a sponge with the inevitable rust issues that would cause.

I will look it up when I get home later as I was planning to pick some up a while ago for another project.

One other thing and I think it is important to note - A whine from the diff that starts to get louder quickly can be a sign of serious diff issues, in the case of one that is quiet until you lift off the throttle it can be a sign that the spool of the diff has cracked or the cross pin is failing. Either situation can sometimes be obvious from under the car if the rear wheels are lifted and the car is put in gear while idling, the diff output cups will appear to wobble.
It is hard to see but if you look carefully in the below picture you can see a crack by the crown wheel running from the cross pin through the cast iron spool.

[Hairyscreech]

I just found the video I was looking for the other day, the rear of this car is jacked up and it is running in gear, by slowing/stopping one wheel the drive is sent to the other wheel and you can see the effect of the cracked spool on the diff output flange. Wobble Wobble.

This car was quiet as a mouse until you backed off the throttle and it began whining.

http://vid159.photobucket.com/albums/t1 ... b80109.mp4

[XVar]

I don't no if it has a limited slip diff the year is x reg 2000

If you give your VIN number to any BMW dealer they can supply a print-out of original, optional fittings. A limited slip diff is denoted as :- 'Sperredifferential 25%'

Or just put the last 7 digits of your VIN here: http://www.bmwvin.com/

I've never actually seen this information in English before, the lookup site I used previous returned the results in German (as mentioned above). Not sure what Power: 142 refers to though since the 2.8 is 192bhp from the factory.

Edit: The 142 is 142kW, as per the wiki for the M52 engine: https://en.wikipedia.org/wiki/BMW_M52