This is one of the most strange things in this game (another one is the body rigidity costing 1/2 price of the car).
Anyway, what gives me hopes for "fully adjustable" transmission later either at higher levels (waiting to be unlocked) or by patch (an omission which to be fixed?) is the fact that you can see adustment buttons for each gear but you cannot go the cursor above them.
I am sure it will be fixed (or unlocked) soon... It's just stupid as it is now.