My 1998 Grand Cherokee has an automatic 4WD system - no locking hubs or controls to select for 4WD - not clear to me what system it is or how it is implemented. In snow, for example, if the rear wheels start to slip, the front wheels automatically receive torque and pull the car.
A worsening problem I have with it seems to occur when negotiating tight turns (e.g. parking) after driving some distance at highway speeds. The wheels hop - seems as though all the differentials are allowing little to no slip. The car has about 167,000 km on it and I've had all the recommended service performed.
I have been told that the solution is to replace the oil in the differentials. Is this the solution? Could I have missed this as a regular service item? If it is a fix, what is the explanation for old oil as the problem and fresh oil as the remedy?