[ImolaM3Vert]

So I’ve recently bought an auction E83 with 170k miles as a daily as I needed an SUV and was pretty familiar with the E46 platform. I’m getting absolutely stumped on what I think is possibly an xdrive related fault.

At low speeds in parking lots I’m getting a horrific clunk noise when turning or letting off the throttle in first. It bangs a few times in the rear shaking the whole car. It’s almost as if the rear diff is trying to find which axle to engage.

When I first bought the car it had a 4x4 light and I only had the opportunity to drive it a few blocks with no tags. I replaced the transfer case fluid (and reset the adaptations via ISTA) and it already had a new servo motor installed. I also replaced the bent lower control arms and blown shocks. That problem ended up being the reluctor ring on the axle.

I really only noticed the clunk after I replaced that and got tags for the car.

Over this weekend I drained and filled the diff fluid on both the front and rear. I planned on replacing the subframe bushings as I’d seen movement with the car jacked up and shifting from reverse to drive but the bushings appeared to be in good shape. I did notice however that the bolts were VERY loose so I torqued them to spec. After that I also got and alignment and reset the steering angle sensor and the clunk persisted.


My next plan of action was to replace the guibo and CSB but I took the car out in the first snow storm of the year and the clunk went away completely. Didn’t matter if I was driving normally or doing donuts in a parking lot, it was completely silent.

It wasn’t until I pulled into a parking garage that it came back. This has me wondering if it’s an xdrive computer issue. The tires are the same size but different models from front to rear but the same on each axle. I did buy them used as the ones that came on it were completely flat. Is it worth throwing a new set of matching tires on all 4 corners or does it sound like I might have some sort of other mechanical problem?