will putting 40deep tyres on the front and 45deep ones on the rear make any difference on a 4wd car?
Could it make the car think that cause of the different diameters the wheels are spinning?

if nothing else it'll put alot of extra load on the gearbox / transfer box...

don't know what car you've got, but if you did that on an XR4x4 you'd knacker the centre LSD

I wouldn't on a 4x4 car,it'll wind up the transmission,and if its modern,ie with tc etc confuse the brain somewhat!

I wouldn't on a 4x4 car,it'll wind up the transmission,and if its modern,ie with tc etc confuse the brain somewhat!