Will the 335d differential (2,81) fit on the 535d (2,65)? And the X3sd diff (3,23)?

As we know most of the remapped 535d can easily do 280 kph. So i took that speed and made these comparisons on 6th gear:

Diff ratio----------RPM------------Speed (kph)

--2,65------------4000-------------280 (stock gears)

--2,81------------4000-------------260 (335d diff)
--2,81------------4300-------------280

--3,23------------4000-------------230 (X3sd diff)
--3,23------------4900-------------280

 

The numbers are wrong. I meant 270kph of top speed and therefore:

Diff ratio----------RPM------------Speed (kph)

--2,65------------4000-------------270 (stock gears)

--2,81------------4000-------------254 (335d diff)
--2,81------------4250-------------270

--3,23------------4000-------------220 (X3sd diff)
--3,23------------4900-------------270

One cons on top speed run on this cars is that the gearbox take too much time to change 5th to 6th due to higher drag at 260 kph (5th gear at 4900rpm). So if the 5th were shorther it would change to 6th easily, and it would be faster on the other gears too. So on 5th gear:

--2,65------------4900------------260 (stock gears)

--2,81------------4900------------247 (335d diff)

--3,23------------4900------------215 (X3sd diff)

After this numbers the 335d diff ratio would be perfect for our cars. Maybe this is one of the main reason why bmw claim that the 335d is a bit faster than the 535d.