i just pulled one of these apart. it was the rear on a 843 but the drawing above looks the same .after you take the big bolt off the inside you can just slide the splined sprocket off the end of the axle.you will need to take the bolt off the other side also to make room for the sprocket to slide off. on the machine i worked on the weld holding the sprocket to the splined hub was broken ,that is, in the drawing above part #3 was seperated into two pieces. the factory only welds these on one side. the part from bobcat cost about 450.00us so we had this one welded ,the shop where we had it done has a lathe so after it was welded on the inside they releaved the flush side and welded it on that side also. getting the wheel hub off the axle was another thing . i ended up pulling the axle out all together, that is hub, seal ,bearings ..... you have to pull the axle out to get the sprocket back on with the chain in place....you have to get the wheel hub off to put the seal i tried to press the hub off with my 20 ton press and it wouldn't budge. the welding shop had a 80 ton press and it did the job. we haven't reassembled the machine yet but as i see it the bearings on the outside go on first then the seal .put the wheel hub on and slide the axle in , the inside bearings go in then someone holds the sprocket with the chain on it in place, while another person pushes the axle in and rotates it to line up the splines, bolt everything up tight (sprocket bolt torque is about 450 ftlbs. i think) put the covers on ,put all of the hoses back on reinstall the stearing levers and trim panels and your up and running. well that only took 2 min. to type but i expect it'll take the beter part of a day to do.