Spring 2025 update.
The car spent the winter in a nice heated underground garage just a few kilometers from here. The first two items on my list were to look at the cruise control and at the rotating knocking noise coming from underneath that started not long before I parked the car last fall.
First hick-up, both batteries were dead. My fault, I should have disconnected them, not only rely on the main battery switch. So I now have 2 new batteries.
I took the car to a local shop to see if they could pinpoint where the noise was coming from. They were not able to pinpoint the source, but fixed a loose exhaust bracket, but everything else looked solid. They recommended that I go to to a shop that specialize in drivetrain to make sure that everything is indeed good.
The rotating knocking noise (toc - toc - toc) is from solid metal, not sheet metal (It is hard to explain, but I am sure that many know what I mean). The noise is there at low speed only. We went to the drivetrain specialist this week. the opened-up and inspected the differential and found nothing wrong there. this was a great opportunity to clean it up, replace the gear oil, etc. The rear axles were solid, so no issues with the bearings. They removed the driveshaft and it was in like new shape (I had the U-Joints, center bearing, etc. all replaced last year). Both ends of the driveshaft showed no sign of wear.
They however noticed two things. First the transmission mount is showing signs of wear. It is still good, but I will replace it anyways. Second, the transmission output shaft seems to have excessive play. From what they could see it looks like the bearing at the back of the transmission may have seen better days. However, they are not a transmission shop so this is where their investigation stopped.
The good news is that the driveshaft and the rear end are in tip top shape. I have an appointment at a transmission shop in about a month. This will be a good opportunity to replace the transmission mount, change the oil and replace the leaky transmission oil pan gasket.