E39 rear transmission noise

Hi folks, I've been away from BMWland for a few years, it's good to see you are still here.

After 21 years my 1998 523i saloon has just started making a noise in what sounds like the rear transmission at around 45 to 50mph. There are no vibrations to feel through the bodywork or steering wheel. At first i thought it was tyre noise (Michelin Cross Climate) but it sounds more like a universal joint or some sort of rotating gear hitting a resonant point? It is definitely road speed related, not engine speed.

I know noise can be deceptive but it sounds as if it is from the rear. It's not a rough noise like a wheel bearing going nor a metallic noise, it's not squealing; I can best describe it as a "not very loud firm and muffled" sound from something rotating at road speed.

Before I start crawling under the car (age is catching up with me as well as the E39 !) is this familiar to anyone?

 

I once had budget tyres on my 525 E39 and they created a mechanical noise, I did not believe it could be the tyres and I spent ages changing suspension bushes and checking wheel bearings, but when I finally changed to a premium brand tyre the noise disappeared. What tyres do you have?

 

Thanks Kleynie. I'm running on Michelin Crossclimate tyres. I do a low mileage in the BMW and up here in Scotland a four seasons tyre is useful. The Michelins are noisier than the Vredstein four season tyres I had before, they were really quiet, but it's a more constant rolling rubber noise. The noise I have now sounds more mechanical but following your message I just checked tyre pressures and wheel nut torques, all were as they should be. More test driving needed, I just need a smooth stretch of road (hmmm find one of those these days) without too much traffic where I can change speed to "tune" the noise in and out.

 

Don't rule out tyre noise. 'Heel and toe' wear patterns can generate noise, common to sound very much like a bearing about to fail.

Good idea to try different road surfaces, that can help you see any intensity changes, also whether a constant sound track, like a mechanical component.

Peter

 

Just for a test try putting 10/15psi more in the tyres to see if the sound changes.
Or even lower the psi just to test.

 

Peter, Alan,

Thank you for your replies. I did think it was tyre noise when I first heard it but then a few weeks later it seemed to get louder so I started to suspect a mechanical source getting worse. Thinking back the louder noise was on a stretch of road I rarely drive so possibly a quite different surface. My next move is to travel in the back with my wife driving, I may be able to get a better fix on the source. My E39 has fold down rear seat backs so I may be able to hear more precisely into the boot area We shall see. I'll be back. Thanks again.

 

Hi Mogman, welcome back to the fold

Good to have another Member in the 'Frozen North' & congratulations on the e39, generally acknowledged as one of BMW's finest models. I used to love my 528i.
I hope the mystery noise will soon be the thing of the past & you can get on with enjoying her to the fullest.

 

Thanks Slim_Boy, When I bought the car out from being a three year old company car in 2001 I only intended to keep it a few years. I'd had a BMW 316 in 1985-1987 and not been very impressed so I had no tie to the marque, but as an engineer and driver the E39 really grew on me. A local non-franchised specialist (sadly no longer working here) told me to hang on to it if I liked it because this range "was the best built BMW to date", and still is I reckon.

 

Are you anywhere near Inverness? If so, Jimmy Cruickshank is your man.

 

Welcome back Mogman , am another who thinks it could be tyre related , different types of tyre make different types of .road noise

 

Thanks but no, I'm near Dunfermline.

 

Thanks Verbarthe, I'll be taking some test runs this week weather permitting.

 

I assume that you have checked there is oil in the back axle? Or if it has done a highest mileage, maybe an oil change in the axle may help - I know BMW say it is filled for life, but in my book no oil can possibly last for life!!
It isn't something silly - like the self levelling suspension pump running when it shouldn't? Assuming yours has that!

Rich

 

Hi Rich,

Thanks for your suggestions. I agree, BMW never thought "lifetime" oil meant 22 years! I had my gearbox and my diff oil changed three years ago when I realised I'd be keeping the car a while longer than I ever expected, it made a real difference to the gear-change, so much smoother.

My E39 does not have a self-levelling suspension pump, I'm used to them on Land Rover Discovery suspensions.

When the snow has gone off the roads around here I'll be out for a test drive to try a selection of road surfaces at the critical speed of 45 to 50 mph.

 

My E39's were all tourers, so I wasn't 100% sure if the saloons had self levelling or not - rules that out at least! I think I would be inclined to think tyre noise, as has been suggested, or it could be a rear wheel bearing, bearings can make some odd noises at times, whirring, rumbling, often increasing when you turn a corner, as it loads the bearing that bit more. If you have never had them changed, it could be that, you haven't mentioned the mileage, but if it is highish, that could also indicate a need for change. I have never changed a rear one, but I believe lt involves a fair bit of work and a large puller!!

Have you checked the driveshaft joints for wear? Is the rubber gearbox flexy OK - I know the mounting holes can wear which might make it run slightly out of true - just a thought!!

Rich

 

Hi Rich,

It's done 120k miles with regular servicing, about time for things to start failing and being difficult to get apart. Once the roads around here are clear of the last slush and not so wet that you can't hear the road noise properly, I'm going to do a tyre noise test run sitting in the back with my wife driving and with 2/3 the rear seat back folded down so I can hear the rear end noises better. I've tested wheel bearings on other cars so i know what you mean by cornering to put load on, it doesn't show any extra sound that way, I've tried. The sound seems more central so prop-shaft related or both rear tyres? We'll see.
Thanks for the suggestions.

 

The roads are back to something like normal so a test drive today with the rear seat backs folded forward to get a better earful of the noise. The muffled even rumble is always there once the car has been driven a couple of miles, as though grease has to warm up and thin? The same noise is there no matter what tyre noise I am getting off the road so I still don't think it's tyres. The sound doesn't change as I put load on the and off the diff by accelerating and decelerating so possibly not the diff. The noise is absolutely related to road speed not engine speed and peaks at around 45 to 50 mph. I can't make the sound change by cornering, loading the near or offside wheel more than the other. This leaves drive shaft bearings I guess? More to follow.

 

A couple of years ago, I had a 200 mile journey driving back from the South East. On the M42 around Birmingham the speed of the traffic reduced to around 40 mph due to road works for approx. 10 miles, and I heard a 'droning' noise - very similar to a faulty wheel bearing. It was related to road speed rather than the engine. I drove a good distance with my window down and could hear it echoing off the armco crash barrier, so it was definitely somewhere on the running gear. Once I joined the M6 Toll, I increased speed and the noise seemed to fill the car. I eventually got onto the M6 proper and the noise eventually disappeared. The following day, I went out to try and replicate the noise and the car sounded completely quiet and normal. I did ask the dealer a short time later to check the wheel bearings and they said there were no faults. Since that day, I've never heard the noise again. When I asked the forum members for advice, a couple of people suggested that it might have been due to a stone stuck in a brake caliper. I know that it's a long shot, but you might just check your brake callipers to ensure that they are clear.

 

Thanks Mieke,

That's an interesting reply. The wheels will be coming off soon so I'll get an opportunity to follow up on the brake pad idea.

 

OK folks, thanks for all the responses. Now that the roads around here are free of snow, ice and deep puddles, I might even say they are dry again, I've given the 523i a run to test for the noise. I am becoming more and more convinced it is tyre noise. Time will tell but if that's the case I can live with it. They are Michelin Cross Climates, I don't know if they are known for noises?