All Balls Racing – Driveshafts & U-Joints, including upper shaft jack shaft bearing and seal kits for the 08-09 Ski-Doo MX Z 500 SS Trail, the 06-07 MX Z 440 Racing LC and the 15-17 Arctic Cat ZR 4000 EFI, plus lower shaft track drive shaft bearing and seal kits for the 1995 Ski-Doo Formula MX Z 454, the 2006 Freestyle 300F and the 08-09 MX Z 500 SS Trail. These kits bring the bearings, seals and retainers that carry drive load from the clutch through the jack shaft and into the track. Snow and water get everywhere on a sled, and once a seal opens up the bearing washes out, runs dry and starts pulling the shaft out of alignment, which chews chaincase gears and track drivers next. A rebuilt shaft spins true and quiet, keeps the track tracking straight and puts the engine's power down instead of into vibration. Set track tension and alignment once the shaft is back in, because a new bearing under a loose track will not last. Upper and lower shaft kits are not the same part, so send your year, model and which shaft you are servicing and we will confirm the right snowmobile drive shaft bearing kit before you order.