On the early variations of the #70, the front shaft was removed by pressing out a roll pin that holds the drive sprocket on the shaft, then pushing that shaft out through the chain side. Later #70's and as far as I know, ALL the #71, that sprocket threaded on to the shaft. Hold the chain side of the shaft with a cresent wrench (grip the 2 flats where the chain sprocket attaches) and thread the drive sprocket off the shaft, then push shaft through to chain side.
On the rear, you'll find a set screw at the very tail end of the chain housing. Back that out. At that point, with the chain side sprocket removed, the axle shaft should push through to the closing wheel side. If there's significant wear or a build-up of dried grease, they can be a bear to get moving.
I've got a parts manual on the #70 with a detailed exploded view of the parts involved, which gives you a btter idea of how to remove and re-install. Email or PM me with a fax # and I can copy the pages you need and send them your way.