Golf 4 4Motion: Humming Noise Front - Diagnosis

I'm having a problem that sounds like the sound of a truck rolling on the highway.

In my opinion, it comes from the front on the right side.
It usually only happens when I'm accelerating quickly or if I hear it while giving the gas.
It will not run below 1200 RPM, and this is only possible with the gear engaged and the clutch disengaged.
When I press the clutch pedal, it disappears. When I'm in neutral and not pressing the clutch pedal, it's also gone.
Regardless of the gear and starting at approximately 30 km/h.
It's also present when the brake is pressed and a gear is engaged for uphill driving.

Okay, briefly put, it only happens when a gear is engaged and I'm in "drive" mode.

What I would rule out is: the brake (because it remains engaged even when released), and the wheel bearings (because the noise doesn't change during turns).

I suspect it might be the driveshaft, but I'm not particularly sure. Perhaps someone could briefly explain a method for checking it, or even have a better idea of what it could be.
I am looking forward to your suggestions.

Greetings.

Okay, if I understand correctly, the noise disappears when the clutch is engaged and reappears when the clutch is disengaged (even when the car is stationary).

No, it only starts at 30 km/h.

To rule out a problem with the differential, for example, drive downhill in neutral and then slowly apply gas until the drivetrain is free of tension (ideally driving straight to help eliminate the driveshafts as the cause). If the noise disappears at this point, the problem likely lies there. The lack of tension almost completely relieves all bearings and rotating parts. It's definitely worth a try.

No, unfortunately, the squealing noise doesn't go away even when I slowly accelerate uphill.
Regardless of the gear and speed.
If I slightly engage the handbrake, the all-wheel drive disengages, and then the noise remains.
"I've also noticed that it sometimes makes noises when driving through curves (especially sharp, fast turns), and the noise disappears when I drive over bumps in the road."
Sometimes, it also briefly stops working after I drive over a pothole.

Could the intermittent nature of the problem be related to a change in length of the driveshaft?

Would a part designed for front-wheel drive also fit?

Best regards, Thilo.

It's likely either a driveshaft or a wheel bearing causing the noise. If I can't pinpoint the exact source, I'll disassemble the joints (on the wheel side) and inspect the balls and their raceways. Often, a small piece of the rolling surface on the raceways or balls has broken off, which then becomes audible during turns (a clicking sound). Sometimes it helps to have someone else listen to it.

Today I drove for a longer period again and had a nice ride outside the city where I could test [something].
Okay, just like you said, if I give the mountain gas, the humming stops.
So it seems the problem is indeed related to voltage fluctuations in the powertrain --> could it be the drive shaft, as suspected?
Would a front-wheel drive version fit, or does it have to be one specifically from the 150 hp/manual transmission 4-Motion model?
Greetings.

Unfortunately, I don't know if drive shafts from a front-wheel drive vehicle will fit.
You should also consider the differential or differential bearing, because when driving straight on a smooth road, nothing is moving in the drive shafts. However, the sounds are different. I don't know if you're familiar with the typical transmission noises of older T4s; in those cases, it's usually the tapered roller bearings of the differential, which sound somewhat like a tram. With the drive shafts, it's more of a metallic cracking sound. But both types of noise are speed-dependent. If you're not sure, start by checking the drive shafts, as the joints can be replaced individually, making them much cheaper to fix.