406oc.co.uk

Apparently something got overloaded when I accelerated and snapped (very sudden loss of power, faint clunking noise afterwards), and I'd like to get some qualified guesses to find the offending component before sending the car to the mechanic. I am guessing that the cold weather we have now must have made the components more brittle than normal, as I would have thought the car to be grip-limited, especially on winter-compound tyres (and also because I would have thought the car to be dimensioned properly for the 314 Nm HDi, and thus give some headroom for the 267 Nm V6).

Since I was in a very low gear when it happened I think that the problem is between the engaged gear and the wheel, and not between the engaged gear and the engine. Which components should I poke and have a look at?

Have you lost drive to the front wheels? Check drive shafts first if so,

(sorry your question is a little confusing/hard to understand)

Sorry for not expressing myself more clearly.

Yes, I have lost all drive to the front wheels. The loss of power was sudden (a snap), and happened during acceleration. If it had happened in a higher gear I would be more inclined to suspect something between the gearbox and the engine - i.e. the clutch, but it wasn't, so I also suspect it to be a drive shaft.

Do you have any schematic over how the power is transmitted for these cars? As I have understood it the differential is almost an integrated part of the gearbox? Are there any other potential culprits that can be inspected, other than the two last pieces of drive shaft that connects to the two front wheels?

When you put in in gear, do you hear any grinding noise?
popped drive shaft
or
Spline ends of one of the shafts might have gone if so, never seen one go on a 406 but worth a check,

There is no grinding noise. There was a cyclic thumping noise regardless of the gear selection (i tested 3rd after it broke to see if it would have power - it didn't), much like you'd expect from something rotating freely at a low speed and not being supported correctly by a bearing. The frequency (or rather: thumps per second) might have been 2-3 Hz. The frequency did not appear to correlate to vehicle speed or respond to the clutch, but I can't say for sure (turned off the engine rather quickly after it had happened).

Jack the car up, place on Axle stands for safety
and check the drive shafts going into the gearbox ,

Thanks, I'll give it a go and report back when I know what has happened.

No axle stands necessary - the right driveshaft (between the differential and the wheel) is broken cleanly at an angle of 45 degrees relative to the longitudinal axis of the axle. Will post pictures later.

Was able to see the stub from the differential by opening the bonnet and looking down the right side of the engine. When I got down on the ground by the headlight I could also see the wheel-end of the broken driveshaft. Hopefully nothing else was broken with it, in which case it may not being as expensive as first feared.

Glad you found it at least! Pictures will be interesting, not heard of this happening before.