Cloupler U-Joint broken (Nitro Vee) Replace with Traxxas part #3527 and or #3528 Outdrive U-Joints broken or loose Repair or replace with Traxxas part # 1539 (Blast/Nitro Vee) or part# 1539R (Villain boats) Clutch is worn or missing (Nitro Vee) Replace clutch with Traxxas part# 3126 One or more drive shafts broken or missing Inspect and Replace drive shafts. Loose Setscews Inspect the yokes, prop, and pinion gears for tight set-screws. Debris caught in props Remove debris and clear props and shafts of stray items such as: weeds, trash and fishing line. Jammed gear train Open pinion/spur gear area and inspect both gears for damage and for items lodged between the two gears. Electric motors locked up, dirty or damaged Give the motors a thorough cleaning and then install them back on the motor mounts