Can anyone advise me ?I’ve Lost drive to back wheels without any warning

[jody391]

That is very true! if as you say the machining was poor it would only weld the mating surface.

Good point!

[ScottR400D]

I think the outer layers get hotter quicker than the core. The process needs to be very carefully controlled to be successful. 

It's widely used for all sorts of shafts especially drive shafts. 

[Gridgway]

It's possible and possibly probable(!) that the centre machining is just to locate and the weld is only intended to be at the edge for a certain depth in.  Right in the middle there will be no heat from friction, a bit like an instantaneous centre of revolution.

I definitely don't think it's a one-off bodge job, but a failure of the welding process somehow.

[aerobod - near CYYC]

With a weld only 1/3 of the radius from the outside diameter, a shaft would still have 80% of the torque transmission capability of a shaft that was welded for the full radius (due to strain from torque being proportional to the 4th power of diameter), so a material problem such as the lack of proper heat treatment or weld contamination would be more likely, than an issue with the depth of the weld.

[Gridgway]

Ooooo, I never knew that.  You don't come across many things proportional to the 4th power!

[Geoff Brown]

So......how many cars are driving around with this time bomb ?  One will never know until becoming unlucky.

 

[SLR No.77]

Who says it's a time bomb Geoff?  It may well be a "normal" method used during gearbox manufacture that nobody would know about until one fails, and this failure might be the first?

Stu.

[aerobod - near CYYC]

In terms of inherent design related time bombs Geoff, I think the big one that is almost a certainty is that there are hundreds of R400D Duratec engines that will have inlet valve spring failure at some point. It depends on what the time period the specific valve spring and cam combo was used as in my 2012 car, to the number affected and how much high rev use the car has seen (all 8 of my inlet valve springs had broken at about 10,000km of track use, 40,000km total use, with the fatal double break of one spring).

[Geoff Brown]

Thankfully I do not rev the guts out of my Duratec !