Diffs dont have to be changed.. IMO
Many have changed tire diam, hence Cirumf and run OEM diffs.
(Tire width doesnt matter to the gearing of the diffs.)
It will give false speedo/mileage readings with larger/smaller tire diam/circumf...
.........but TOD etc will all still work as long as all 4 are matched.
And if you do change diffs... as some, including me have....
...you must change both
Jo
.