After starting work and taking off the lower guard of the engine, the mechanic told me that he had never changed the transmission oil of Mercedes-Benz, and I was speechless. Then came a mechanic who claimed to have worked at the Mercedes-Benz 4S Store. To be honest, I had some doubts about his experience of working at the Mercedes-Benz 4S, because he said the code name of the five-speed gearbox was “722.9”, but then he was adept at saying the group code and name in the WIS. I suspect this person may not have repaired the Mercedes-Benz for a long time.

When it comes to emptying the old oil part of the torque converter, this part focuses on writing. The mechanic who changed the oil for me said categorically that the oil in the torque converter could not be released. “if there is no oil in the power drum, it will be broken.” I explained to him for a while, when the mechanic who had worked in the Mercedes-Benz 4S also came and said that he had never changed the oil in the torque converter at the 4S store. I did not approve, called the store manager, the manager smiled and said to me, the torque converter in the oil is impossible to change, his apprentice is now working in Mercedes-Benz 4S, you can call to ask. So I asked him to call, and the reply I got was “it’s okay to change, or not to change.” So the mechanic began to study where the drain bolt on the torque converter was. I reminded him of the two rubber plugs under the position of the torque converter, which would expose the bolts by removing them. Once again, he said firmly that it was impossible. “there are observation holes, not oil bolts.” I had no choice but to show him the video I found on the Internet, and then I removed the two plugs. After removing the plug, they found that they could not find the location of the drain bolt, so they called the man who is now working in the Mercedes-Benz 4S and knew that they needed to turn the crankshaft to expose the drain bolt. After removing the bolts, the old oil was discharged, and when I installed the oil pan, I reminded the mechanic to use a torque wrench, but he said, “Don’t worry, it’s already in place, there must be no problem.” I insisted on using a torque wrench, which began to be fastened with standard torque.

Because the machine is equipped with oil conduit, the oil cannot be pumped from the lower part of the gearbox, but needs to be filled from the engine compartment. When filling the oil, the mechanic was faced with the black oil dipstick pipe plug in the engine compartment. Finally, I told him the method of disassembly and assembly to get it. The Beijing Automobile Club store could not find a funnel suitable for the filling conduit of the 722.6 gearbox, and finally made a simple funnel with A4 paper to pour the oil into it. The standard dose in WIS was 7.5L, and then changed to 8L. After filling about 7L of oil, I started the engine, idled, switched gears, and made the tire run for about 5 minutes. At this time, the oil dipstick is used to measure the liquid level, and the liquid level is a little below the scale line at 80 degrees. Touch the temperature of the oil with your hand, which belongs to the kind of temperature that is not hot but somewhat hot, and it is estimated that it does not reach 80 degrees, so stop filling. Here is the first question in this post: is it too little to add 7L gearbox oil? Does it not meet the minimum conditions for the operation of the gearbox?

After coming out of the Beijing train club, I ran about 50 kilometers again, and I didn’t feel any significant difference after the experience, but I felt that there was a delayed shift in the gearbox just after filling the car for the first time (the speed of the gear shift was higher than usual, usually about 2500 rpm). I don’t know if there is an oil change protection program inside ECU.

Calculating the cost of this oil change, 10qt oil is 775 yuan, transmission oil dipstick is 24 yuan, filter set is 67 yuan, and working hours are 160 yuan, totaling about 1,000 yuan, which is more than half cheaper than 4S oil change. It is acceptable to me, but for Xiaobai, I still recommend going to 4S for oil change, because based on my experience of oil change this time, I found that if you change oil in a place like a roadside store, unless the technician is particularly experienced, it will definitely be debated over whether to drain the old oil from the torque converter and whether to use a torque wrench. People who have no experience or don’t know much about cars may be “fooled”,”We have never seen anything like this in all the years of repairing cars. According to what we say, it must be true. Whatever is said on the forum is wrong. The guidance document is just a guide. If you follow that, you will have to repair the car sooner or later.” If you don’t have the ability to cope with things like this, go to the 4S honestly.

This post can be regarded as a personal record of changing gearbox oil. It is also a guide to share some experience with everyone. For Xiaobai, who has just joined the forum or does not understand car maintenance, it is a guide to avoid pitfalls.