Bert Transmission L.W. Spool 31/33 CTD-200-17 - Bert and CTD have been working with Tiger Rear Ends to further improve the rear drive with the innovative smart spool. The spool is bored and splined through with the industry standard 31 spline design. The outer portion of each side of the spool is machined with a larger 33 spline pattern. The smart axle is shouldered (similar to a driveshaft) eliminating the need for the axles to butt against each other. (with adjusting bolts) The result is a two inch saving in axle length. Added to the 3 inch saving of the smart drive system translates to axles which are amazing five inches shorter per side. The weight saving is equal to cutting ten inches off an axle and every bit of it is unsprung weight.