THE KNOWLEDGE
Key to the technical success – and the modest cost – of this repair was Darren Gardiner’s frankly virtuoso skill in adapting an essentially scrap 987 Cayman drive shaft to work safely on our 986 Boxster. The 987 shaft is visibly larger in diameter than the 986 item, but there seemed no reason why that should be a problem, and crucially both items have the same overall length – give or take a little bit of ‘stretch’ in each of the constant-velocity joints.
No, the biggest issue, it seemed to me, was going to be the ABS ring. On the 986 shaft it’s just that – a ladder-like device wrapped tightly round the outer end of the outer CV joint, where that passes through the hub carrier – but on the 987 the required signal is generated by the sensor ‘reading’ the wheel bearing, and there is no ring, as such. Darren was confident he could remove one of the two rings we would be left with from the old shafts, and fit it to the Cayman part, but with the CV joint on the latter not only slightly smaller in diameter, and also with a marked taper, I was sceptical. How would we get it in the right place? And what would we weld it to?
The first step, obviously, was to take the ring off the old shaft. It was most likely shrunk on; that is to say it would have been heated to expand it to slide over the cold shaft, and then to grip it as it cooled and contracted. This suggested that, perhaps with the aid of some further heat, it could be gently tapped off, but we soon realised that would be difficult, if not impossible, without irreparably damaging it. So Darren carefully cut through the ring with a thin angle-grinder blade, and although it was still firmly stuck in place by the protective paint sprayed over it, some cautious levering with a screwdriver blade soon prised it free.
The next stage was to work out where the ring needed to be positioned over the 987 CV joint, and this Darren achieved by measuring back from the outer end of the two splined drive shafts, ie old and ‘new’. That gave him a datum point for the inboard side of the ABS ring, and then he carefully ground away the paint in the relevant area to allow the weld to ‘take’ on bare metal. The ring, too, he cleaned up with the grinder – all this done free-hand, I might add, with the confident dexterity of a practised surgeon – and having made sure the cut ends were neat and tidy, he welded those back together to create a full circle again.
How, though, to secure the ABS ring such that it was not only concentric with the CV joint, but also with its outboard edge effectively floating in thin air? Having deposited four small blobs of weld at 90 degrees around the circumference of the joint, Darren ground them back – again by eye alone – until the ring could be slid over them and more or less hold itself in place. More measuring, a little more welding, some gentle tapping with a hammer, and he was satisfied – and if you study the pictures I think you would have been, too. Some gentle finishing with a fine-grade grinder blade, to take off the external burrs, and the job was more or less done.
All that remained, given why we had the use of this shaft in the first place, was to grind back the paint on the remainder of the metal outer cover and seal the potentially leaking seam with first some paint from a rattle can and then some black silicon, with the same material squeezed into the air gap between the ABS ring and the joint as a further means of securing and protecting it. (The sensor would not ‘see’ the silicon, relying instead on counting the metal rungs of the ladder as they passed beneath it.) Ready to go!