ball diff adjusted correctly should be fine in the b4 raced against guys with there b4 for years on Calandra green carpet..
Team Associated 9830 Gear Diff Outdrives B4.1 B4.2 T4.1 T4.2 SC10 sc10.2 NOS NIP | eBay
Hot Racing SCT38XH Hard Anodized Aluminum Differential Gear and Cover B4/T4/SC10 ...