DUSTIN - Two things could cause the steering wheel/shaft to raise up out of the steering tube.
First is the preload on the thrust bearings is loose, the BIG potmetal nut on the bottom of the gearbox needs to be tightened just a little. There should be a cotter key keeping this nut from turning You'll have to remove first, a large screwdriver fits in the slots to turn this nut further into the housing, it goes counter-clockwise. This is probably the problem if the wheel/shaft only raise up a little, less than 3/16 or 1/4 inch. The second problem is more serious, the stamped steel race the thrust bearings run on pushes up thru the diecast housing where the steel tube presses into the diecast housing and this allows the wheel/shaft to raise up further. The gearbox is only held in with two 3/8" capscrews, pull the steering wheel, disconnect the steering tierod from the gearbox, raise the front end of the tractor and securely support the frt of the tractor on jack stands and remove the whole housing & tube/shaft for disassembly & rebuild. If the whole tube, shaft, & steering wheel raise up then I would guess You have the second problem, the tube has come loose from it's press fit in the diecast housing, the thrust bearings have worked their way thru the top of the casting. There's a "FIX" for that, I did it to My 72's original box and My old 129. You need a short piece, maybe 1/2"-3/4" long of 1-1/2" OD steel tubing, NOT PIPE, with 1/4" to 3/8" thk wall. Ends need to be really "Square", grind a chamfer on the ID on one end, Then assemble the gearbox without grease, and drop the steel sleeve down inside the steering tube over the steering wheel shaft, tap the sleeve securely into place inside the steering tube against the top thrust bearing with a small long rod or wooden dowel. Drill & tap a couple holes thru the diecast housing, thru the steel steering column tube into the steel sleeve, I used either #8-32 or #10-24 machine screws, only about 3/8"-1/2" long and threaded them into these holes and locked the whole assembly together. Take everything apart and clean out the steel chips from the drilling/tapping, grease everything up real good and reassemble.
I replaced the whole steering gearbox a year ago on My 72 with a brand new one I bought probably FIVE years ago on sale at My local Case/IH/Cub Cadet dealer for over $200. I'm not even sure complete gearboxes are even still available. But they're easily worth brand new what a decent running whole tractor is worth.
I could use a $1,000 bill or two, and not as in addressed to "accounts payable" more like one that has "In God We Trust" on it. 
What you been up too? Thanks for the nice comment on my Original. IIRC you have that nice 100 with the flames on the hood, why would you need to redo it? Isn't this your 100? 
