Really appreciate the information on the L5450. I'm having the same issue with the 4wheel drive. I did the same search as you. Seems everything on this tractor is a little different than others from that age. I crawled under there tonight, and saw the same huge bracket. I'm always overly cautious and was concerned. So very thankful coming across this thread.
My question is once you dropped the bracket and axel cover, was there anything else different I might run into, compared to the other YouTube videos on the same problem or fairly straight forward?
I have already purchased couplings. I'm not a great mechanic but can do the basics.