In the book \u201cOutliers,\u201d Malcolm Gladwell states that it takes 10,000 hours to become an expert in a field, task, sport, the arts, education, etc. Conservatively, I have 84,000 hours in automotive, but realistically it is more like 100,000 hours. I have been living for approximately 550,000 hours. Which means I have spent 1\/5 of my life working on or thinking about cars. This is somewhat depressing, as cars are not my true passion. No matter how many times I feel a diagnosis might be easy, I get surprised with something difficult. A technician could follow the test plan perfectly and still be miffed. This could not be further from the truth as I had a problem with my 2022 BMW X7.\u00a0<\/p>\n
For about three months, I had been feeling a slight shudder or vibration on acceleration in first gear and reverse. I first connected the Intelligent Service Technical Application (ISTA) and pulled codes. The only code I had was a system low voltage code in the digital motor\u2019s electronics (DME). This car was built in early 2021, so it was unlikely, but not impossible, for it to have a problem with the battery. We then cleared the code and I drove the car for a week. After a week, I connected the ISTA again and pulled codes. The system low voltage code was back.\u00a0<\/p>\n
BMW X7 batteries average about six to eight years before they fail and mine was only 5 1\/2 years old. Yet I was hyper focused on fixing my own car. I then replaced the battery, cleared codes and drove the car for a week. The system low voltage code was gone, yet the shutter was not.\u00a0<\/p>\n
I then made sure to check all the basics. Air filter, spark plugs, ignition coils and checked for vacuum leaks. All the basics were OK. The whole time it kind of felt like a motor mount to me, but if it turned out to be one of the basics, I would have been mad at myself. I then checked the motor mounts. The motor mounts were OK. I then started checking further back in the powertrain. Transmission, propeller shaft and rear differential. While checking the propeller shaft, I noticed a lot of movement in the transfer case. The transfer case is mounted between the transmission and rear propeller shaft. The interesting thing about the 2022 X7 is that the transfer case mount is also the transmission mount.\u00a0<\/p>\n
Now I\u2019m super excited, because this shudder has been driving me crazy and I\u2019m going to fix it by replacing the transfer case mount. I looked up the procedure and ordered the mount. By the way, there is nothing easy about doing anything with this transfer case. The mount is pressed into a cross bracket that sits between the frame and transfer case. We then received the mount and installed it. After installation, I drove the car and the shudder was gone. I was so happy until the following day.\u00a0<\/p>\n
At the end of the day, I was parking my car (in reverse) and the shudder came back and it felt worse. It was one of those moments when you sit in your car and scream!<\/p>\n
How could the shudder be gone for a day and come back even worse? I then drove the car around the block. I could feel it when I was performing tight turns. This is where it gets really interesting. If I felt this type of shudder in an AWD car on tight turns, I\u2019d know there is a problem with the center differential or transfer case.\u00a0<\/p>\n
When I got to the shop the next day, I planned on performing a transfer case service on the X7 as soon as we could. Again, nothing is easy with the 2022 X7 transfer case. Not only can you not just drain the fluid, the ISTA has to be connected to allow the fluid to be pumped to a place where it has to be extracted with a large syringe. We then performed the service, which took about three hours, and I test drove the car. The problem was gone, yet I was not going to say anything until I drove the car for about a week.\u00a0<\/p>\n
After a week, the problem was still gone and then I sat down with my staff and discussed the problem. After looking at all of the environmental data we concluded that since my car is driven in the snow every weekend during the winter, the transfer case works harder than cars that do not go into the snow. We also run snow tires in the winter and they create more friction on the road. This also makes the transfer case and related parts work harder. The reason the problem got worse after the transfer case mount was replaced is that the new mount was stiffer. The old mount was weak and was absorbing some of the shudder. Your transfer case should always be serviced to the factory specifications, but if you drive in the snow a lot, do it sooner and also replace the mount. Thanks for reading.\u00a0\u00a0<\/p>\n