Whirring noise from 406 Auto Gearbox when cold?

Hi,

I have a 1997 406 3.0 SE Coupe with auto box and just clocked-up 200k
with no real problems until recently (but read on).

Started to get a whirring noise when starting the engine which seems
to be somehow related to the viscous clutch on the automatic gearbox.
This noise gradually settles down after driving a few miles (i.e. the
gearbox has warmed up). It's been gradually getting worse (louder,
more evident) over the last few weeks. Noise is directly proportional
to engine revs and appears in all gears including Park and Neutral.

The whirring noise reappears when the engine is heavily loaded (i.e.
accelerating hard) or when braking heavily (the auto box will change
down to assist engine braking). Noise disappears again when driving
normally/steadily.

I've also noticed that when cold, sometimes when slowing down/braking
the auto box will disengage - the engine revs drop to tickover even
though I'm probably still doing 30-40 mph. I've also now realised this
has been happening from new - every now and again when cold the auto-
box would suddenly produce a big 'thunk' when slowing down and a
consequential jolt in the car - basically the auto box was disengaging
and then kicking back in to create the jolt. Again it only ever
happened when cold.

Otherwise the car drives fine.

Obviously the car's getting a bit worn now, so I think there's
something related to the viscous clutch. But I don't really know much
about the internals on an auto box!

Dealer has run a diagnostic test on the box and found no problem -
apart from low gearbox oil. However that's now all topped-up and
there's no change. I don't really want to take it back to the dealer -
they're really saying the only thing they can do is strip the whole
gearbox down and look to see what the fault is - my confidence level
in them finding something wrong and fixing it though is not high!

Suggestions anyone????

Cheers,
Richard.

 

changing the gearbox oil to full sythetic oil such as Castrol Trans Z may
help. I've found Peugeot auto are fuzzy on oil and the semisynthetic oil
specified doesn't seem work very well. It's worth a trial, a lot cheaper
than stripping the gearbox down.