Whining noise - Gearbox, Diff??? Hmmm

[Cottis]

So i have a whining noise on my 3b that seems to be most apparent at 2500rpm+ in 3rd and 4th gear. Nothing in neutral. It increases in volume and slightly in pitch as speed increases. Starting to think it is not engine related but maybe the box or diff.

Every gear engages fine, nothing ever pops out, no clunks or crunches. Mileage is just over 150k and I assume it is the original5 speed box.

It will be going in for some brakes in a coupla three weeks or so, so will ask matey to have a look but couple of questions are:

1. Would a knackered box or diff reduce speed of car. It just seems slightly slower than usual but of course that could be something entirely different.

2. If the box is knackered, would I be right in thinking it is pointless sourcing a used one as they are weak points if the my research is anything to go by. Seems better to buy a 2nd hand one, have it totally rebuilt, install it and then use my old for the same in the future if it happens again.

Never had a box or diff go before so not sure what noises I should expect. I would make a recording but I dont think it will come out very well on top of general engine/cabin noise. It has only really started doing it, so not too bad at present but assume it will worsen.

Damned car was running faultlessly for 2yrs+ and just getting a couple of annoying headaches having just done the Aux Rad, Cambelt and Aux belts ha ha. Typical but you gotta take the rough with smooth. Only surprise is that it worked so well for so long before something went awry.

Cheers for help or any suggestions based on experience

[Error404]

If it's road speed and not gear or load dependent I would say it's probably a shaft bearing or front diff carrier bearing
Rear diff noise IME is quite easy to hear it coming from the rear of the car.
Bearings for the 01A are not too expensive actually, compared to the 01E. If it does turn out to be the gearbox I would definitely rebuild if you plan to keep the car at sensible power levels. Getting a good used box is a wager with really bad odds these days

[Cottis]

Cheers Alex, pretty sure it isn't road speed related as the noise stops as soon as you come off the throttle and then starts again as soon as you put your foot down (assuming you are 2500rpm+) Fairly sure it seems to be coming more from the front of the car than the rear, so kinda plumping for the box unfortunately as it appears to be under load when it happens. How much is a box rebuild these days and any advice on where to take it? Next problem is that I cannot remove it myself and take it to a rebuilder. Get the feeling this is going to be big problem. If I knew I could source a box which just needed pinion bearings (assuming that is what it is) then fine but when you buy something 2nd hand, I think you have to assume worst case scenario. As I want to keep the car for some time and also keep the power as it is (somewhere around 350bhp maybe) I would want a full rebuild I think. Could do without this at present.

[Error404]

So just to clarify:

No noise when stationary
No noise when coasting (off load)
Increases in pitch with road speed
Increases in volume with road speed
No change through different gears

?

[Cottis]

So just to clarify:

No noise when stationary
No noise when coasting (off load)
Increases in pitch with road speed
Increases in volume with road speed
No change through different gears

?

No noise when stationary CORRECT
No noise when coasting (off load) CORRECT
Increases in pitch with road speed CORRECT
Increases in volume with road speed YEP ATFER 2500rpm until turbo kicks in at which point you cannot hear it because engine is making more noise
No change through different gears I never thrash 1st, 2nd gear doesnt seem to be a problem but third and fourth it is audible, cannot tell in 5th as at that speed, there is enough cabin and road noise to drown it out if its there. Below 2500rpm in fifth it is quiet

Initially I thought it was the turbo giving up because it seems down in a power a bit. The power available is still very consistent, no boost cuts or anything like that. My mate who used to be a mechanic came out with me the other day and said it didnt sound like a whistling turbo to him. It is more a cross between a whine and possibly the quiet dentist drill type noise. No smoke out of the back of the car. Turbo is K26 Hybrid that has done approx 35k and is always warmed up and down properly by me. I cannot speak for the first 25k of its life though but I would think it should last longer than this as it was a new unit in 2008 about 35kmiles ago.

[Cottis]

Oh and apologies for welcoming you into my world of awful mechanical explanations ha ha.

[Christophski]

Andrew, it sounds similar to what I had for ages then my head went and turbo was knackered so sorted them out and since then no whines..... Gearbox noises are more grinding sorts of noises compared to a whistle. You sure it's just not a tiny boost leak or something simple?

[Cottis]

Andrew, it sounds similar to what I had for ages then my head went and turbo was knackered so sorted them out and since then no whines..... Gearbox noises are more grinding sorts of noises compared to a whistle. You sure it's just not a tiny boost leak or something simple?

Hiya Chris, hope you are right. I can deal with a £500 turbo rebuild rather than a gearbox out job and total rebuild. I don't have equipment or knowledge to do a boost leak test, so am only able to check what I can see and access (which isn't enough) It is going into MRC next friday for a healthcheck and will ask them to leak test it. If that shows up nothing, I will need to take my mechanic out in it to replicate the noise for him so he can pass judgement. Recent belt changes probably meant front off and maybe a couple of boost hoses being taken off and put back on. Maybe something was not put back quite right. Was thinking of a full roose kit to future proof it to a degree but with recent cambelt, aux belts, aux rad and full service not to mention replacing front brakes, I thought I would leave it a few months. Might order them on Monday. Cannot hurt I guess

[Christophski]

Silicone hoses will help but won't solve boost leaks Bud as they mainly come where the jubilees oval upon tightening.... Just nip the jubilees up a bit and see if it helps. Sure MRC will tell you what it is and hope it is a leak or the turbo rather than head or gearbox. If it's not grinding I doubt it's the gearbox bud. If it is that then it's probably still ok until you get grinding too then you can try to play a tune with the whistling and grinding together lol. Just hope for your sake it's not the head but you would be getting all manner of issues if it was that too.

[Cottis]

Pretty sure it is not the head. Would be seeing other symptoms I think. It uses no water or oil and not making any funny engine noises. If it does, I am blaming you for mentioning it ha ha ha.

Will update on Friday next week. I think Alex had gearbox issues, so hopefully he will be along later to pass a bit more judgment on my garbled confirmations to his questions.

Was going to get a new daily but might put that on hold now until I know how much I need to spend on this. S2 takes priority over the dagdag.

[Error404]

I'm sure MRC can have a look & listen in person. I will say your symptoms sounds very similar to the issues I had with a gearbox bearing. Never opened it up to find out which one it was, shaft or diff carrier bearing probably as like yours it was road speed dependent and not affected by gears but mine did it coasting in neutral too. I ran with it like that for over 6k hard driven miles with a few days on track too and it got very marginally worse during that time but not significantly.... so I wouldn't worry too much at this stage if you can't hear it over the road noise once the speed picks up.

HTH

[Christophski]

I seriously doubt it's what I mentioned (I'm not saying it again lol) I hope it's a hose somewhere or turbo bud but like Alex said, it could be your gearbox but I thought it would grind a bit too. I'm not expert and it's just my thoughts and alex has way more knowledge than me so listen to him more than me bud. Hope it's a cheap solve for you though.