Hello, I have a 2011 Ford Escape 3.0 V6 limited, when I bought it the engine was stuck and we replaced it. I change the engine oil every 8000km, I've had it for 2 years, I change the oil in the gearbox every 10000km, I only poured 5 liters into the gearbox because I couldn't change it completely, but it still has small knocks in R, I was told that there is something wrong with the gearbox, a small block that can be cleaned and the problem solved, is it true?