We are currently running an Escort in Tarmac events and are currently changing diffs to 3.6:1 in the front (basically standard ratio) and 4.1:1 in the rear. We have new gears and morse chain for the transfer box to get a 1:1.148 ratio between front and rear but the ratio between the two diffs is 1:1.138. Obviously this small mismatch will cause the viscous centre work a bit. Does anyone know whether this amount of "slip" in the viscous is a problem, it seems to me it only a bit over 1% so should be ok but some knowledge would be good.