If you have both axle housings off the center section, unbolt the trunnions from the front frame. Drop the center section down and pull it frontwards to disengage the driveshaft and cover. Throw the center section on the bench and remove the pinion shaft. You do have a repair manual? If not get one, or hire the rest of the repair done by someone qualified and in a position to back up the work if something goes wrong. Ring and pinion setup is not for novices. You are looking at over $500 just for a new R&P; bearings, seals, shims are extra.