The front axle never needs a friction modifier and the rear axle only needs it if it has the optional Tracloc limited slip differential.
However, probably 99% of the appropriate GL-5 gear lubes already contain friction modifier for use by a limited slip differential. The additive is compatible with all axle types with or without a limited slip differential so most lubricant manufacturers include it just in case the vehicle has a LSD.
You can verify if the gear lube has the friction modifier by looking on the label on the back of the bottle and looking for wards to the effect of 'compatible with limited slip differentials' which means it contains the friction modifier additive.
Your Jeep has a Dana 35c in the rear and a Dana 30 in the front.