406 diff whine - is it a problem?

[stripped fred]

There is a whine coming from my 406. Not too bad and has been like that since I got it. I think it's the diff but I suppose it could be the alternator or something else? It goes up with engine revs. The gearbox is fine and changes well. Assuming it is the diff should I a) ignore it, check the gearbox oil level and top it up if needed or c) change the gearbox oil completely? I suspect some will say changing the oil might do more harm than good but I don't really understand that as surely new oil will be better than the old stuff in there? Just trying to keep it going as long as possible. Will it just stay noisy and keep going or is it near the end of it's life? Ta.

[Dave_Q]

Deffo top up gearbag oil, think the fill hole is behind the ns wheel on the end of the gearbox.

 

Probably nothing terminal, but if its related to engine speed rather than road speed it's not the diff, a noisy diff would also probably sound different under acceleration, coasting and deceleration.

[stripped fred]

  On 05/05/2016 at 09:38, Dave_Q said:

Deffo top up gearbag oil, think the fill hole is behind the ns wheel on the end of the gearbox.Probably nothing terminal, but if its related to engine speed rather than road speed it's not the diff, a noisy diff would also probably sound different under acceleration, coasting and deceleration.

Of course, didn't think of that even though now i do it's pretty obvious! Think I need to investigate further then. Will check the alternator then as could be that. Or something else inside the gearbox?

[Dave_Q]

I honestly wouldn't be too concerned, the last car I drove with an actually fucked box sounded like an accordion or something on acceleration.

 

Check the levels but really, a serious problem makes a serious noise and if you're noticing a slight whine you've probably just been driving the same car for too long.

[steve_earwig]

Oooh, 406 diff whine, don't hear that much. If you're topping up the oil you may or may not find a level plug. Much easier to drain the lot out and stick 1.8 litres 75w80 in through the reversing light switch hole (18mm I think)

[dollywobbler]

My XM has had a gentle transmission whine the whole time I've had it. Only really noticeable at 50mph, which is why towing the caravan is a little annoying, and only in fifth gear. I keep meaning to change the oil, but was putting that job off for when the clutch gets done, seeing as driveshafts have to come out.

[ruffgeezer]

does the whine remain if you dip the clutch?

[flat4alfa]

A shreaded pair of nylons is favourite for shutting up an old diff.

[sierraman]

Lots of old Peugeots have diff whine especially at high mileage. It won't get better but it'll go for thousands before it becomes a problem. Are you sure it's not the wheel bearing?

[flat4alfa]

That's what I thought too

 

Put some sawdust in anyway, just in case

[stripped fred]

I think I may have got it wrong as it does it when stationery too. It can't be the diff then can it? Increases with engine revs, clutch in or out. Thinking it might be noisy alternator bearings?

[Anthony]

Yup, won't be anything transmission related if it does it when stationary and unchanged clutch in or out.

 

Might be alternator bearings, or one of the idlers/tensioners on the aux belt or cambelt. The aux belt ones in particular can be both noisy and troublesome in my experience, assuming that it's the same setup as a 306 HDi.

[Stanky]

Get a bit of garden hose and hold it near, but not TOO near, things like the alternator and anything else belt-driven. You should be able to hear which of them (if any) that the noise is coming from if you hold the other end of the bit of hose to your ear.

 

it worked for the noisy alternator bearings on the Saab.

[stripped fred]

I'll have another look before I waste anyone else's time! The garden hose method sounds useful. Thanks for all replies.

[beko1987]

Ooooh keeping an eye on this thread, sounds like my issue (whine related to speed not revs, starts at 50, vanishes over 80, doesnt change with clutch, steering, braking or shouting)

 

I've ignored it for now, although I'm wondering if it's explaining my lack of power compared to prior to the whine

[steve_earwig]

Duff tyre?

[sierraman]

Might be a drive belt idler. Or even a partially seized tensioner. I'd take the belt off and check the idler for roughness, then with some plusgas work the tensioner in and out. While you've got the belt off you might well change it. Could be alternator bearings, there should be barely any perceptible end float in the pulley.