Cupra ST 300 4drive, problem with differential hum? please help

[Reactor]

Hello!
I am sorry for my English.
I have a problem with leon St cupra 300 4drive.
I had a hum from the rear axle, in 7500km the rear differential was replaced. The hum seemed less, but now it's quite noisy.
This happens when taking your foot off the gas from 100 to 70kmh. It is also in the N-shift position.
Does anyone have a similar experience? How can this be solved? It is very unpleasant.
Now the hum from 110kmh and more has been added, this time when the throttle is added it can also be heard from the rear axle.
It's louder than the first hum. But it wasn't there before. Wheels and tires are fine.
I've never been on a racetrack or tried to drift in the snow.

Thank you!

 

[Damo H]

No need to apologise for your English. It’s better than a lot of the natives lol

Couple of things to check:

Was the hum there before the differential was replaced? And was that 7,500 from new?

What are the tyres like and make. I know you’ve said the tyres are fine, but run your hand across the rolling surface backwards and forwards. See if you feel a sharp edge from the tread blocks in one direction compared to the other. If so try swapping with the fronts. If it’s odd tyre wear due to a bad alignment, the noise should reduce.

Maybe worth paying for an independent garage to service the Haldex rear Diff. And take pictures of the filter housing. Heard horror stories of them being serviced with wrong oil etc. So a possibility if it’s been swapped.

If the car has done less than 10,000km I wouldn’t expect things like bushes to be worn or wheel bearings to of failed, but maybe worth checking for any okay on anything.

 

[Reactor]

The hum was about 2500km. I had a winter r18 bike dezent, service told me to come when you have the original r19. They checked the wheels, tires, bearings. They changed the oil in the haldex (it smelled like a burn) and then changed the diferencial because there was a lot of metal in the oil.
I thought it was less humming, but now it's a lot to hear again. I have 20,000km. Tires conti sport 6. Winter goodyear ultragrip.
it roared even in the snow, it's not tires.
It also doesn't look like a bearing.
Haldex works.

 

[MATT RILEY]

The rear diff has two oils, the haldex oil and then the actual diff oil. Have seen it before where a garage would drain the diff oil and fill it with haldex oil causing damage to the diff. Check this first.
Also another thing to check is the front transfer box bearing where the prop is bolted on, check for any play in this.

Hope you get this sorted fella.

 

[martin j.]

Mistakes with oil would be my first guess, heard of it before, not just Seat can make this mistake.

 

[Reactor]

I was in an unofficial service. The rear brake discs were wavy. Everything else looks fine. Now the brakes are replaced, but the hum is still there: - (((( Now the car will go to an authorized service center.

 

[Norbert]

I hear some hum noise i think from new. 100% back section.not too loud and i cant hear all the time.I had old bmw common issue with diff and that was really bad like wheel bearing.
I can live with it but i think you not alone. My car done 5.000 miles yet.

 

[300bhpdaily]

Sounds like saw toothed inner tyre wear. Having said that most techs would have sent you a vid on the health check if that was the case to up sell the tyres. Did you have any mention from the garage about needing rear tyres due to uneven wear? if I was you I’d put the rear tyres on the front and see if the noise moves to the front. If it does it’s the tyres if it doesn’t investigate further my friend.

 

[Reactor]

I flipped the tires from the front to the back. The hum is the same on summer r19 and winter r18.

 

[300bhpdaily]

Oh dear ok well we can rule the tyres out for definitely then.