So it had been decided that the grumbling noise from the rear of the car was either the differential or a noisy CV in a drive shaft. Many thanks to Ian Haynes, Ben Smith, and a chap called Simon who I’ve never met who clubbed together to deliver a spare drive shaft to me at work today.

This evening I drive up to Robin’s and we investigate further. Various tests with the rear wheels up suggest to us that it’s probably the differential rather than the drive shafts. As we’ve disconnected the drive shafts already to test, and Robin has a spare open differential, we decide that it’ll be just as quick to swap the differentials over as it would to change drive shafts.

Craig Smith, the man who lent me a spark plug tool in my hour of need wanders in to say hello as we’re just getting to work. There are some pictures of all this somewhere on Robin’s camera – I’ll update again as and when I receive them.

Once we’ve got my LSD off we get it on the bench for an inspection. There’s certainly a fair bit of play in the offside bearing. Due to various complications Robin’s open diff doesn’t have its back plate on. We drain away his old fluid for disposal, and whip the backing plate off the LSD.

We transfer the oil from the LSD to the open diff (we know it’s not the right specification – given the short term use of the open diff we decide it doesn’t matter – anyone who knows different please let me know!). Having taken the backing plate off my LSD we notice that the speed sensor is badly damaged – see below:

As far as we can deduce, the failing bearing (which probably failed due to the suspected oversteer kerbing by a previous owner) caused the metal spinner which passes through the speedo sensor to come out of alignment. It would have hit the sensor rather than passing through its two prongs, damaging it. Our theory is that under positive load the bearing moves into a position where the spinner passes neatly through the prongs, but on the overrun the negative load moves the bearing out of shape to the spinner’s blades hit the sensor.

As we stand, it’s rather ironic that the LSD’d car I hunted for so long currently has an open differential! Still, this is temporary. It is lovely to drive without a nagging “I’m broken” noise in the background, and the car seems more tractable – less resistance in the bearings possibly, or maybe just the different final drive ratio.

So I’m now left with an LSD without a backing plate that may as well have all its bearings replaced. I also need a new speed sensor – I notice the ETK reckons that part isn’t available separately.

I know Ian and Simon have ideas about getting the LSD sorted, so I’ll be looking into those shortly. If anyone has any other ideas, or knows of a source of speedo sensors, please let me know.

Finally, I’d like to re-iterate my thanks to those who’ve helped source this half shaft that I haven’t yet used. It is appreciated, and at the very least I plan on keeping it in stock – we all know it could well be required one day!

The 330d has had a relatively quiet month. It’s had a quick trip to Wales in the snow for the Wyedean rally, but otherwise has just pottered around the south east, barely notching up 500 miles in the process. Fuel economy has therefore dropped to the appalling trough that is 38mpg. Oh dear, what a pity, never mind.

I’ve finally taken the time to attempt to repaint the alloy I kerbed back in the autumn – the result is okay – I imagine I could get a better finish if I spent more time on it in a warmer climate, but until the summer at least, it’ll do.

While removing the rear nearside wheel for painting, I noticed that the suspension spring that side has snapped, as is usual, almost at the bottom. This is quite common, and the car just sits fractionally lower as the spring effectively becomes shorter. The spring on the other side was broken when I got the car, but I didn’t notice until an eleventh hour pre-Nurburgring departure check back in April 2006, and my local dealer only had one in stock, so I didn’t have the time to replace the pair. One spring on the shopping list then.

I have made some progress on the juddering brake problem that has plagued me since I returned from the ‘ring last April. I’ve sourced a pair of Rossini drilled and grooved front discs, and they’re now proudly on display on a garage shelf. I must say they certainly look the part – magnificent in size and design – I hope this transfers to performance, but before it can I’ve got other hurdles to jump.

Firstly, which pads to use? I’ve got some Red Stuff pads in the garage, but I’ve heard mixed reviews about these to put it politely. Still, they’re here and my wallet would certainly prefer that I didn’t buy any more. Certainly I could justify using them in order to bring the magazine’s readership my findings, but would that cloud my judgement of the Rossini discs?

I’ve got time to muse over that because I want to replace other things when I change the brakes. I’ve got a theory that I cannot justify, but it says that juddering brakes could be brought on more rapidly by worn front suspension, most notably the wishbone rear bushes and ball joints. I really like the idea of replacing all these parts at the same time that I change the front brakes, effectively renewing a large chunk of the front of the car before it reaches the 100,000 miles “run in” mark. As I’ve got a set of the wishbone rear bushes already in the garage, I investigated the cost of two new wishbones (the ball joints are integral to these parts). BMW want… £200 each! Ouch! More research is required, especially with the M3 and (less interestingly) home decoration shaking my money tree.

Still, the 330d does deserve it; prior to this month it has cost £80 plus fuel to run since October. That said I’ve bought my annual tax disc which marks the impending one year of 330d ownership. I managed to avoid the horror of mingling with the great unwashed at the post office by using the magical internet – the tax disc was delivered to my door a couple of days later as promised. In the shadow of all this debate about travel tax it’s still a wrench to stuff £195 into Gordon’s pocket, but I can’t blame the car. It’s done another good job this month, and at the very least it’ll get its new spring, and maybe even its new wishbones and brakes on before you next hear from me.

Mileage since last report: 542
Total Mileage: 93,384
MPG this month: 38
Cost this month: £216.89 – brakes