47-55.1 Need help with Wipe arm linkage set up on my 51.

[65blackfleetside]

So long story short this has been an 18 month build. I put all of this wiper linkage together with new aftermarket motor but with what I believe to be? the original wiper linkage over a year ago. Fast forward 1 year to now i have more electronics, AC ducts, wires etc under the dash than a 747- And Now I cant see sh*T. And I dont remember much about this part of my build. It sucks getting old.

(Pictures coming soon of my completed build in different thread)

This linkage on drivers side has a small spline shaft 5mm ish and then a larger diameter (12mm ish) set of double splines pushes over top of smaller one.
See picts

Problem: This assembly just pushes through with nothing holding it on the back side.
I am missing something here? It seems as though the wiper gear assembly should be bolted from the inside or some type of retainer clip.