640D Ownership Dilemma - HELP!

[nmirza]

Hi all,

I am hoping to get some thoughts on a dilemma I'm facing with my ownership of the 6 series I currently have. It is a pre-LCI January 2015 640D Gran Coupe M-Sport. This is going to be a long read so grab your popcorn and fizzy for this one.

I bought the car back in July 2023 and below I shall give some background as to how the relationship has been going with the car thus far and if it has come down to depart from the car already.

So following on from first purchasing the car, it threw a 'Driveline Malfunction' error when accelerating. Diagnosis of this issue threw up a code of 244C00.

In order to get to the bottom of this issue the following works were completed under warranty in August 2023 -

-Pressure Sensor pre turbo replaced
-Vacuum Pipes replaced
-Pressure convertors replaced
-DPF Pressure Pipe (failed and replacement fixed code)

Following on from this the car had just done 70,000 miles so booked it in for a ZF8 Gearbox service/oil change in August.

Front Tyres changed in November due to a mishap with a sharp curb, don't feel comfortable changing 1 tyre.

In December is when I started feeling this odd vibration from within the car at motorway speeds. At this point is where the journey begins into this oddity so I had wheels balanced which got rid of the vibration.

I booked the car in for Interim Oil and Oil Filter service in January 2024.

Unfortunately in February rear left tyre lost air pressure rather quickly, found out nail in tyre so replaced rears as well.

Vibration in the car is back and felt at motorway speeds but also through the brake pedal. So all 4 Discs and Pads replaced in March as they had warped. Vibration gone from braking now but was still there between 60mph to 75mph.

When I had the car booked in for the Gearbox Service the mechanic noticed weeping from Diff and advised getting Bushes/Propshaft bearing and Flex Disc replaced. So started off by replacing the Flex Disc or Guibo and the Prop Shaft bearing in March as well. My mechanic noticed at this point that the existing Prop Shaft bearing housing had been damaged by whoever was underneath the car last. But also rather interestingly that the PropShaft was non-OEM. So propshaft bearing and housing replaced.

Vibration still there and now I notice it from about 35mph+, it is at it's worst at 74mph. It is not rev or gear related as it happened only with the speed of the car no matter what driving mode it is in. Vibration is felt through the steering wheel, front footwell, base and back of the seat. There is an audible rumble through the car as well, almost like a change in air pressure within the cabin.

I sent the car in again with my mechanic who now carried out a dial/run out test on the alloys and noticed that the Front Right and Rear Left were slightly out. So I booked it in for a specialist to have them straightened however they said my alloys were fine and there was no issue with buckled alloys. Wheels balanced again, vibration still there.

So next as it was on the to-do list I had the diff seals replaced and all diff bushes as well in early April however vibration remained.

I thought since I don't know the car that well I went to have a 4 Wheel Hunter Alignment however the mechanics there could not complete it as all tie rod ends had seized so these were replaced as well in April. Hunter Alignment complete however vibration still remains.

As I was perplexed by the dial out test and told the alloys were fine, I wanted to negate this side of things completely and my very nice friend lent me his E92 M3 Tyres and Alloys and give them a run out. Unfortunately, vibration still remained - noted that it wasn't AS prominent as before but I put this to 19" alloys rather than 20" and also non-RFTs.

SO I took the car to a BMW specialist in Crawley just outside London and they had a technician sit with me to experience the vibration. They are attributing the sensation to possibly being the Prop Shaft.

Now here is where it get's interesting if not already - the Prop Shaft they are offering is a special order in from Germany, totalling around £1600 supplied and fitted. The other alternative is to get the existing one balanced at a specialist which are hard to find for much cheaper.

The car is booked in with them next Wednesday to investigate the prop itself to determine it's current condition. My dilemma at this point is this - if it is the prop that is the cause of this vibration which I hope it is as I've not had a clear answer for months now; do I go down with just having the existing one balanced and just get rid of the car? OR install an OEM prop and keep the car knowing there has been 1000s spent on it.

My worry is if this doesn't fix the vibration issue - I'm at the stage where I feel like a total mug putting this much money into a car that technically speaking isn't even that old and shouldn't require this much maintenance surely? I can't keep giving the wife the usual adage of well this could have happened within any second hand/used car we bought.

I'm not looking to getting certainty from people of what the issue could be, but more advice on where to go from here.