I have a 2008 model Mahindra 6530 4x4 with about 700 hours. When i put it in reverse it sounds like the gears are grinding. Tractor will still move but the loud grinding noise continues until i take it out of reverve. I have changed the hydro fluid and filter and cleaned the screen, also opened the inspection plate to look at the gears, i don't see anything wrong but i can't see everything. Does not do this in any forward gears. Anyone experianced this problem before or know what the problem might be?