Hello, I have a two questions, maybe this one can answer me. 1. How much and which oil actually comes into the four-wheel coupling. (my last info was 75W90 Hybrid OIL) 2. Is an oil filler opening available? if yes where? This has the following reason: I was told that the oil has penetrated into the transmission housing, and thus there is too little oil in the four-wheel coupling housing. Due to the few oil the lamellae could not work properly. My theory is, I Just fill in oil and can delay the expensive repair a bit. The oil has penetrated into the gear box seems logical to me, because according to the measuring rod I had too much oil in the drive so let off about 0.5L, because too much oil can be as harmful as too little. But it is not tragic if the oil from the four-wheel coupling mixes with the gear oil. I thank you in advance for your support Walter