The Pro-Built® 4X4 front differential comes professionally assembled for easy drop-in replacement. The sealed assembly comes pre-filled with 30k-weight silicone oil with steel gears to withstand Velineon® brushless horsepower. Pro-Built differentials are direct replacements for VXL 4X4 models (see full list below). Includes 13-tooth pinion gear and 37-tooth ring gear. (Pro-Built differentials are not directly compatible with Titan®-powered 4X4 models) Accessory part(s) for these models: BIGFOOT 4X4 BL-2s 67134-4 Ford Fiesta ST Rally BL-2s 74154-4 Ford Fiesta ST Rally VXL 74276-4 Ford Raptor R 4X4 Ultimate 101177-4 Jato 4X4 BL-2s 90154-4 Jato 4X4 VXL-4s 90386-4 Rustler 4X4 BL-2s 67164-4 Rustler 4X4 VXL 67376-4 Rustler 4X4 VXL Ultimate 67097-4 Slash 4X4 BL-2s 68154-4 Slash 4X4 VXL 68386-4 Slash 4X4 VXL Ultimate 68277-4 Stampede 4X4 BL-2s 67154-4 Stampede 4X4 VXL 90376-4