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Q: Car wouldn't shift properly and driver saw smoke - 1995 Mercedes Benz S320

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One day recently, the transmission had stopped shifting, but now it is shifting again. Previous to this, the night before the speedometer backlight had gone out. The next day while I was driving, suddenly 4th gear dropped out and would not work. I managed to pull over to the side of the road and I saw smoke. Then, my car wouldn’t shift into 2nd gear, but it would still drive in 1st gear. Two days later, the speedometer backlight came back on and I’m now able to shift properly again, with no problem. To test it, today I accelerated all the way to 80 on the interstate and there was no smoke, and the shifting and down-shifting are working perfectly. What caused the shifting trouble, the smoke, and do you think it will happen again?

Hello. I would first recommend having a full vehicle inspection performed by a qualified mechanic. The smoke could possibly be due to a fluid leak landing on the exhaust. The transmission may be leaking fluid, which could also be causing the shifting issues.

It is also possible that the issue only occurs when the vehicle gets hot. After a day or two of cooling down, the vehicle may take a few miles of driving before the symptoms reoccur. If something is not right with your vehicle and the problem stops randomly, it is very likely that the problem will reoccur.

After the full vehicle inspection has been performed, you will know if any fluid is leaking from your transmission or not. If no fluid is leaking, a more in-depth inspection will need to be performed to determine exactly where the smoke is coming from. Once the source of the smoke has been located, the cause of the smoke will be easier to determine. As for the shifting issue, if no fluid is leaking from the transmission, the issue may be electronic and may have thrown a trouble code. If this is the case, it may be a good idea to have the vehicle scanned for trouble codes. To have the problem scoped out in detail, a certified technician from YourMechanic can come to your car’s location to diagnose the shifting problem and smoke firsthand in order to have this repaired properly.

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