Thread: What is this sound!

I couldn't quite work out how many times the noise occurred over a set period of seconds because the "chimes" kept beeping ....however, my initial impression is that it's some sort of 'sympathetic resonance' vibration.

Can you replicate the sound by giving the engine a "blip" with the accelerator pedal while stationary in the driveway or does the vehicle have to be moving at say (guessing here) 60+ kmh?

Does it matter if the engine/exhaust is fully warmed up or not?( ...thermal expansion may be part of the explanation)

If it only occurs while driving then it's fair to assume it's driveline related...

Does the rhythm of the "brr... brr... brr..." sounds vary with the speed of the car or with engine rpm at a steady speed?

Even though panels etc of whatever size appear to be properly secured, they may still vibrate. Double check all the fastenings of the components mentioned by others in these posts.

If it's driveline related and speed dependent, I'd suggest carefully checking UJs and CV joints for undue "play" to begin with...

(Hope this helps...can be most frustrating ...if not...pls forgive my lazy Covid lockdown musings... !

Originally Posted by Macadamia

I'll see if I can get to them without removing the wheels, otherwise will check on them next time I rotate.

Give them a tap with a large screwdriver or similar from under the back. If one rattles or vibrates then it needs to be removed and repaired anyway.

some closure finally as I didn't get anywhere with popping heat shields on and off.

The D4 went in for a service today and they called to say the prop shaft bearings had collapsed and I could either replace the bearing or the whole shaft. They recommended the whole shaft as the replacement bearings are poorer quality.

I was already planning on getting the alloy coolant distributor installed while it was in so it's turned into quite a pricey service >_<

Well there you go.. centre bearing carrier

Originally Posted by Macadamia

They recommended the whole shaft as the replacement bearings are poorer quality >_<

OEM replacement bearings should be fine. Propshaft may need to be rebalanced, but full replacement is of course nicest and easiest.

Originally Posted by Eric SDV6SE

OEM replacement bearings should be fine. Propshaft may need to be rebalanced, but full replacement is of course nicest and easiest.

No workshop in the UK worth it’s salt refits bearings.
Not one has had the repair go the distance.

New shaft is the go.

Originally Posted by Tombie

No workshop in the UK worth it’s salt refits bearings.
Not one has had the repair go the distance.

New shaft is the go.

This is one thing I don't understand, nearly every modern rwd vehicle has a 2 piece shaft and the bearing can be replaced, must be somewhere like hardy Spicer that can do it properly.

Originally Posted by loanrangie

This is one thing I don't understand, nearly every modern rwd vehicle has a 2 shaft and the bearing can be replaced, must be somewhere like hardy Spicer that can do it properly.

It’s a plain bearing in a rubber skirt slid on the shaft with a retaining clip or similar. I just did the exact same replacement of an almost identical part in an 80s BMW. The only difference is how the centre of the shaft separates to access it. The BMW has a spline join with a lock collar you unscrew and they slide apart. The Disco shaft join is more complex in this regard with damage possible in the separation process especially in corrosive UK environments. The BMW has balance paint marks on each half you align during reassembly.

What I did learn in the bmw process was that you are supposed ‘apparently’ to preload this bearing by sliding the carrier 5mm to front of vehicle after finding it’s static position on the reassembled shaft. That’s folklore in bmw world.

The advantage of replacing the whole assembly is it’s also highly possible that one of the uni joints are on the fritz by this stage as well and leading to the centre bearing wear. Certainly this was the case for the rear uni on the bmw which was stiff and is not serviceable or replaceable.