Found this thread from here
https://www.volvoforums.org.uk/archi.../t-144353.html
This is similar to what I said earlier :- the early V70 + V70XC ran a viscous coupling which was very unforgiving re different tyre diameters.
Since about 2004 perhaps sooner all 4x4 systems fitted to Volvo have been a Haldex system which could car less about tyres of different diameters.
Cheers
Bob