Are gearbox same, mehatronic and valves?
Is it possible to put 5hp19 gearbox amd diff from 2.5 TDI to 2.7TT and leave ECU and TCU from 2.7TT
As I know they all have same speed ratio only final gear are not same? Or I am wrong

The final gear ratio is different, the transfer case to the front axle and the transfer case to the rear axle are also different. and since the center distances of the gears in the transfer case to the front axle are different, the box body itself is different.

The rotation sensor is also installed on the output shaft to the front axle, so the gear ratio in the transfer case is important. you need to install the final gear pair in your box. It is possible to adjust the gearing.

Allroad 2.7t has its own individual box housing and corresponding transfer case housing and front axle drive gear