The manual says there are adapters for a puller. There is a specific adapter for COE. From what I can see in the pic, it looks like the adapter, which is a part on the end of the puller jack screw, is either resting on top of the threaded shaft or screwed to the shaft. This adapter has a small enough OD to allow the pull bolts to thread. Maybe you can find a socket that fits over that horn stuff, pushes on the shaft, clears the bolt holes and place your puller jack screw on the square drive end of socket. May need a washer on the square drive end of the socket to provide a hole for your jack screw point. Of course a machinist could make the perfect adapter for your puller.

Pic HERE

Let some liquid wrench run down the shaft threads. Maybe it will reach the spline. I'm guessing about all this from a shop manual picture. I don't know for sure. 41-47 AD boys will know.

It seems like the adapter would screw onto the shaft end. Otherwise pushing on the shaft end will damage it's lead-in threads. In that case you will have to find a nut/modify a nut that fits the shaft. Then push on that nut. Maybe the actual steering wheel nut will work OK. Bolts may clear the flats. Steering wheel only needs to be pulled up a little to release. Some folks put the nut on, pull up on the wheel with their knees and bang on the nut. But you have that funky horn thing to stuff out of the way I guess. If I'm all wrong I will delete the post so as not to create bad info, even though a guess.

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