2nd service, gearbox fluid and shock absorbers... (2/2)

Article December 16, 2018

2nd service, gearbox fluid and shock absorbers... (2/2)

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Two weeks have passed by since my last post. Actually the car has been successfully serviced a week ago, however, a few issues appeared, which is the reason why I postponed posting.

“Beaten” oil

The image speaks for itself. Due to the hot summer the oil was pushed to its limits. With multiple Vmax rides on days with +30°C and an average travel speed of 240km/h (45 minutes for 180km including city driving, parking and construction work on the Autobahn limiting speed to 120km/h), it was simply too stressed.

After having replaced the oil it was time to start the car again and listen how much it likes the cheap Mannol. Surprise - it likes it a lot. With the Mannol the engine runs super smooth. Its about the same as I would have used Mobil1 oil.

However, there is a downside with the Mannol. Unlike Mobil1 its not fully synthetic making it a bad oil for short rides. In my case this is not an issue, since I never drive short distances and change the oil in regular intervalls.

Dripping gearbox

While the oil change went as planned, I noticed oil leakage from my gearbox.

At first glance it seemed to be serious, however, WIS reveiled that the issue I was facing was related to GM being savy on 4 screws, bolting the gear and clutch housing together. For some reason they thought 8.8 grade steel would be enough.

To fix it an upgrade to 10.9 grade steel is required. It really took me some time to find those for an acceptable price, yet I ended up ordering them from Schwedenteile. The part number is 55561609.

Unfortunately the bolts didn’t arrive yet, which made me to postpone the gearbox fluid change. Luckily the dripage is not too bad. The gears still shift smoothly and there is absolutely no vibration or whatsover from the gearbox.

Only the differential is making some noises, when the oil is still cold and being in low gear, which indicates that the fluid is worn.

Worn wheel bearing

Another thing which slowed me down was the rear right wheel hub. For quite somewhile I was annoyed by a humming noise, whenever I drove faster than 130km/h. However, I was unable to identify the issue, yet I felt it was related to the wheel bearings and guess what, I was right.

While changing the brake pads, I noticed that the wheel hub was totally fucked. Its a wonder that it continued operation so well. While there was no play, you could hear it grinding. I replaced it with a SFK wheel hub for another 70€. Replacement is a breeze and took less than 30 minutes. All you need to do is to remove the wheel sensor (on the back of the hub) and unscrew 4 nuts. Then you can use a small nut (11mm), put it on the bolts and use a hammer to tap them out.

Its a bit tricky, since its tight, but once you get the hang of it, it really shouldn’t be too much of an issue.

Together with the new shocks the car felt way more stable and comfortable beyond 220km/h. Once the gearbox is sealed properly again, the mechanics should be about right and will finally allow me to take the car to more than 300HP.

Rear shock absorbers

Speaking of the shocks, if you wonder what torque is required for all the screws:

  • Shock to axle - 150Nm
  • Shock to bearing - 28Nm
  • Bearing to chassis - 53Nm

Replacing them takes less than 10 minutes per side. What a noticed during my work was that the spring plates were gone. This might give a squeaky noise when running over bumps, yet its nothing too serious. Fixing this requires the springs to be compressed - in theory.

Practically you can use a second jack and remove the bolt connecting the axle and journal. Then you slowly release the jack and the spring can be taken out by hand. This method is especially safer for people, who never used a spring compressor.

Nonetheless, always be careful when working with springs, since they can easily kill you!

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