Droning sound and slight vibration after differential replacement

[AgentBishop]

First off, Thanks to everyone here who contributes to the forum. It’s a wealth of info that I love to browse through. I apologize for not contributing - I’m more of a lurker and probably don’t have much to contribute anyway.

That said, I need some advice on my 2016 M4 DCT ZCP with 5k miles.

History:

-Purchased in September

-1200 mile break-in service completed in November

-Immediately following the 1200 mile break-in service there was a very noticeable whining noise that is present at 52 mph +/- 1 mph and could be heard most when coasting down from 60+mph to below 50mph on a smooth road. The dealer agreed there was a problem and replaced the read differential.

-After rear differential was replaced and the vehicle was placed back in break-in mode…everything seemed great. The car felt and sounded a little different, but seemed like it was functioning as it was supposed to.

-A few days later, first time on the interstate and above 65 mph, I IMMEDIATELY heard a very noticeable droning sound coming from the front now and some slight vibration in the pedals and steering wheel. Almost as if I had truck tires on.

-Contacted my service advisor about the issue. She asked that I just continue driving (unless I felt it was unsafe) until the 1200 miles break-in period was up and they would look at both issues when I brought it in for service. I agreed.

-Few days later, BMW Corporate/USA (or whatever) called me directly and said they were aware of my issues and were monitoring the situation. I told them the dealership suggest to complete the break-in and then bring it in for service for both issues…we both agreed that was best.

-Finally completed the second break-in period and dropped off for service. After a couple days, my service advisor called me and said the noise I was concerned about is the result of cupping/feathering of the front tires due to aggressive driving (80k car with premium tires that were developed with BMW specifically for this car…a car that hasn’t seen the track yet btw…so any “aggressive” driving around town shouldn’t cause improper tire wear). Which seems plausible, except that prior to the rear diff replacement the car drove super smooth and straight…2 days after service…front end noise starts. I also noticed the car seems out of alignment and pulls to the right after a few seconds. Initially rides straight…but then drifts right progressively quicker. The service paperwork from the diff replacement indicates an alignment was done, but this last service does not. How can you diagnose a problem as premature and improper tire wear, but not check the alignment?

Should I just accept the service departments (which has actually been great btw…) conclusion or continue to persist? Am I just being a nit-picky pain in the ass?

Side question…
When you step on it from a full stop and the rear end breaks loose…does your car track reasonable straight or does it pull to one side consistently? Mine pulls left (rear slides right and car goes left) pretty quickly every time.

Thanks!

Mark

[MN2///M]

So the real question is; are the tires cupped?

If so, I think your only choice is to replace the front tires and have the vehicle aligned; make sure you get a copy of the before and after report for the alignment.

If your drone/vibration is still present, then I'd get a little more adamant with the Service Department.

As far as your other question; depends on the road. I typically don't floor it, instead I manage traction with the throttle. If the road has a crown to it, say middle higher than the outside edge, the car is going to tend to slide with gravity....also, more likely to have some sand/gravel that causes the outside right wheel to lose traction first. I'd say normal unless you are on a perfectly level and clean road.

Are your left and right tire pressures even?

[AgentBishop]

Thanks for the reply.

I haven't examined the tires yet to know if there is any cupping. I brought it back to the dealership because the alignment was off. The shop foreman didn't think it was outside of what's considered normal. I asked him to take a look and do an alignment for me since I don't want to replace the nearly new tires and have the exact same thing happen again. So...they gave me a loaner X5 and said they would call me. Just so happens that the regional BMW technician was in the area and drove/inspected my car and determined the axles and both rear bearings need to be replaced and that the alignment was indeed off and they were having trouble getting it perfectly aligned. Technician said the front tires may be a little cupped but that's not the problem.

The term "buyback" has been mentioned. Has anyone gone through this process with a lease? If thats what they end up suggesting...is it worth doing just to wait for a new one to arrive?