swap 4 speed automatic to 5 speed automatic

[mathieu_p]

Is it possible to swap the 4-speed auto gearbox of a 850 T5R with the 5-speed auto gearbox of a C/S/V70R.
The idea is to chiptune the 850 T5R to 300+ HP and to me a 5-speed seems to be better to handle the power and torque.
What I found on the internet is that the engines are the same, but the questios is: Does it mean you can swap transmissions?
Anyone any idea or experience?

[jimmy57]

No, yes if you have unlimited budget.
There was never a five speed auto trans used in a non-networked Volvo. A custom control module possibly could be made by someone who knows enough to write software to satisfy the TCM with available ECM signals. The ECM and TCM were both substantially revised effective 1999 with the 5 speed first used in 2000.

[jblackburn]

This is screaming for the application of an M56 swap.