Golf 3 TD Variant, problem with driveshaft or differential

For the past few months, I've been experiencing a strange problem with my trusty GIII TD Variant (which has very little rust and is in pretty good condition).
- It runs incredibly smoothly over short and medium distances, with excellent power delivery, and shows absolutely no signs of issues with the engine or bearings.
- On longer highway drives at speeds greater than 150-160 km/h (equipped with a long 5th gear, capable of a true 175 km/h on a flat road), a clicking noise begins to emanate from the front axle on the left side after approximately 160-200 km, at a speed of around 160 km/h. This noise is dependent on wheel speed and load (both pulling and pushing). I can only minimize this unpleasant sound by using a maximum of 20-25% throttle and maintaining a speed above 115 km/h (of course, not exceeding 125 km/h, because at too much load, the clicking also starts). It's most noticeable around 80 km/h, where you can only give it a very light amount of gas. Then, at 110 km/h, you can only cautiously accelerate on a flat road or downhill, after which it works again.
- After about 50 km of very delicate handling of the accelerator pedal, it suddenly disappeared again, and the car was running perfectly again, without any issues! Until the next high-speed section, which will be over 160 km long.
I've experienced this issue for the third time. Also, I've noticed some differential oil leakage on the left side (from the driveshaft seal). It got worse again last time (regarding the coffee grinder, and it was quite loud), but it fixed itself again.
My guess is that the joint on the transmission side of the left driveshaft is damaged. As long as the grease doesn't get too hot, it can compensate for the damage. However, prolonged high-speed driving on the highway can cause the joint to overheat due to friction, the grease becomes liquid, and the damage to the bearing surface in the joint is no longer compensated for. This can lead to loud clicking and knocking noises. After a period of inactivity, the fat becomes firmer again, and things return to normal.
Is that plausible? I suspect that the differential oil seal has become leaky due to the strong vibrations. Could the problem also be related to the differential bearing on the right-hand side (VA), or should we expect further damage to the bearing?
Planned: Replace the left driveshaft and seal. Inspect the differential carefully. Is it possible for someone with experience and good tools to replace the bearings on the left side of the differential if necessary? Is this diagnosis plausible, or should other things be checked (e.g., ...)? Front wheel bearing (left side) or the entire differential?

Has any work been done on the powertrain recently? My question is aimed at determining whether something may not have been properly repaired or tightened.

I would start with the obvious things first.

# Visual Inspection
# Inspection using a tire lever to check for worn or damaged joints.
# Inspect all relevant drive components for any signs of loosening (wheels, axle carriers, drive shafts).

What is the mileage of the Golf? Since when have these noises been occurring?


It can be difficult to translate "Radlager" or "Radlagerung" directly. Detecting wear on drive shafts.

Generally speaking:

# Wheel bearing: the outer bearing is defective. In a left-hand turn, the right bearing receives the load.
# Drive shafts: Accelerating on a straight road and then easing off the accelerator.

"With my Polo 6N, I experienced something similar. Because I couldn't get a precise diagnosis from those tests, I ended up replacing the wheel bearings and drive shafts. It's been quiet ever since. And the effort wasn't much greater doing everything at once." It might also be worth considering for you.

Thank you for the quick response.
The clutch was replaced a year ago, and since then, it has covered over 45,000 km without any issues. The problem first appeared last autumn, then again four weeks ago, and this weekend, each time after driving on the highway at speeds above 160 km/h. Otherwise, there are no other noticeable issues, even on long highway drives up to a maximum of 140 km/h. The car has over 550,000 kilometers on the clock, but the suspension was completely overhauled two years ago (rear axle bushings, both control arms with ball joints, both tie rods, strut mounts, all shock absorbers), so it actually drives like a new car.
Cornering is not a problem on either side, whether driving slowly with a heavy load or quickly with high lateral forces; the car feels very stable and planted. There are no unusual noises (except for a slight squeal from the rear left brake in right-hand turns, which probably needs to be checked and adjusted, possibly the wheel bearing).
A visual inspection revealed nothing unusual, and rotating it or shaking it without the mounting bracket doesn't cause any wobble. Over the weekend, it sounded really bad, and I was already expecting a complete failure. I was very surprised by the renewed self-repair.
I'll need to look at that as soon as possible, and then I'll go through your checklist.

Are these just noises, or are there also vibrations? Based on your description, the transmission is increasingly becoming a suspect for me. Does it shift properly? When was the last oil change (and when were the spark plugs last checked)?

The transmission oil was changed two months ago, and there have been no issues. During the last occurrence, a feedback effect was noticeable on the steering wheel (fine jolts) when encountering loud noises (not just impacts, but also cracking sounds).
I doubt it's the transmission, but maybe it's the differential on the left side.
The shifting is incredibly smooth.

Something broke, and the vibrations made it noticeable.

I'm guessing it's the transmission/differential or the driveshaft. It's difficult to diagnose from a distance.

Hello!

To troubleshoot, you could try something like this:
under the cuff of the inner drive shaft joints.
with a syringe or something like that.
Pour in some oil.

I've experienced this several times before.
"On my old T3 van, and on my Golf Mk2."
It was such a loud crash that nobody wanted to drive anymore.

I didn't do anything else, and then everything was okay again.
The end of the car-sharing service was foreseeable, so I didn't want to undertake any major initiatives anymore.

That would be the simplest and cheapest option for now.

Hi,
In the described "high-speed driving" scenario, the exhaust manifold, turbocharger, exhaust pipe, and catalytic converter get extremely hot, and the exhaust system expands to its maximum extent. Could a component in the suspension be affected, or is something loose internally (e.g., the catalytic converter insert)? Furthermore, joints in the immediate vicinity of the heat sources could also be a factor. Perhaps a heat shield is simply missing? (It might have been forgotten during the transmission installation).
hg
Herbert.

First, I'm going to replace the left driveshaft because I already have a spare. Then, I'll replace the left differential seal because it's leaking a bit. While I'm at it, I might be able to check if the differential bearing on the left side has been damaged, or if the wheel bearing on the left side is faulty. The argument against it is that the car is currently running normally without any noticeable issues.
The AAZ engine does not have a heat shield protecting the engine/transmission. The flexible pipe is positioned so that it radiates heat from a distance of over 15cm onto the engine block, and from above, a small area radiates onto the differential. Only a shield is installed for the footwell area. The catalytic converter is located underneath the floor with shields protecting the underbody and radiating downwards; both are installed.
It's possible that the knocking and cracking sounds aren't coming from the powertrain, and I will systematically investigate all possible causes. In this case, the load and wheel speed dependency could theoretically also occur, but the rubber-metal bearings for the engine-transmission block were completely replaced with new ones a year ago; the old ones were worn out.
I will post the result when I know more.
Thank you for all the tips.

Okay, the day before yesterday, even after two days of not driving, the problem persisted – a loud knocking sound under load when accelerating or engine braking. I only drove the necessary short distances and treated the gas pedal with extreme care, and I disengaged the clutch when coasting. Otherwise, it sounded terrible and even made passersby stop and stare. Yesterday, the bad weather finally cleared, and I replaced the left driveshaft, and the ball joint on the transmission side was completely worn out. Almost 5 degrees of play in the power transmission, I suspect the joint looks bad on the inside.
Assembled and test drive - exactly the same, just slightly better. Differential damage is already feared.
Today I replaced the right driveshaft. The same issue is present on the transmission-side joint: excessive play (not sideways, but between forward and reverse rotation). Thankfully, the differential spins easily and smoothly, without any irregularities or noises, and the pinion bearings have absolutely no play – phew, it seems they're still in good condition.
Assembled, and it runs again like new. That is, the drive shafts had approximately 500,000-600,000 kilometers on them and were simply worn out. The grease had masked this during normal operation, and the knocking that occurred after driving on the highway – although initially self-repairing – destroyed both transmission-side bearings within 5,000 kilometers. "When I have the time, I'll verschandeln them up and post some pictures of them. You can't see the damage in the photos, but you can feel it when you manually rotate the exposed shafts against each other – it's clear that they've been through some heavy use."

LaurenzBo wrote:

Otherwise, it sounded terrible, and it even made passersby stop and look. Yesterday, the awful weather finally stopped, and I replaced the left driveshaft, and the ball joint on the transmission side was completely worn out. Almost 5 degrees of play in the power transmission, I suspect the joint looks bad on the inside. Assembled and test drive - exactly the same, just slightly better. Differential damage is already feared. Today I replaced the right driveshaft. The same issue is present in the transmission-side joint: excessive play (not sideways, but between forward and reverse rotation). ... Assembled, and it runs again like new. That means the drive shafts had approximately 500,000 to 600,000 kilometers on them and were simply worn out.

Thank you very much for the feedback!