We started with a Synergy Suspension Jeep JK D30/44 Complete Inner Axle Sleeve Upgrade kit. For $200, you get the inner axletube sleeves, inner C gusset kit, and lower control arm skidplates. The ball joints are another weak point on the JK front axle, so we ordered a set of Synergy heavy-duty upper and lower ball joints (PN PPM-HD-BALL-JOINTS). Even with the cost of the ball joints, we think that our axle upgrade is a steal at $425.