Although very rare, front driveline vibration may occur at speeds over 35 mph when in 4WD. If this occurs, install the appropriate optional t-case indexing kit. Optional t-case indexing ring kit recommended to reduce front driveline angle. Models with a 6 bolt transfer case use part # D5623. Models with an 8 bolt transfer case use part #D5813. Vehicles with a two piece rear driveshaft and carrier bearing require a carrier bearing drop kit D5405 sold separately. Not designed for factory rear airbag suspension models. Also fits 6.4L Gas models. Will not fit Power Wagon models