what gearbox oil is in it? and is it overfill?. volvo's synthetic gear oil is quite thin, might be worth changing the oil if it's not been done for a while.Low mileage truck is hard to split to low range when cold. When the gearbox heats up sufficiently the splitter works well. What can it be. Perhaps I need to adjust something but I don't know what/how. Is there a workshop manual available online?