MT75 gearboxes don't like 75W 90 oil. Originally Ford had their own specific MT75 oil, the colour and consistency of ATF. I put Ford 75W 90 oil im one of mine once as that what was what the dealer told me they now recommended as they stopped doing MT75 oil. It was horrible and notchy and slow to engage gears. I immediately dropped it out and put Comma MT75 oil in and it was fine. Granville also do an MT75 oil.