Really need to id the transaxle used as Craftsman mower are made by both AYP (Husqvarna) and MTD. I have seen both with the double "D" axles.
Depending how badly the rim is stuck on the axle, you might have to remove the transaxle, disassemble it, and use a hydraulic press to get axle out of the rim. But first try some 2 cycle fuel mix if the rim will move any at all on the axle as it can penetrate better than WD40 as the WD40 just won't soak thru the rust and dirt.
Here I experimenting with a new home brew penetrating fluid that seems the work a lot better than the WD40 or other commercial penetrating fluids that I have tried in the past. The problem with it is that it keeps separating so I shake it up before use. At least it is cheap to make up. Another drawback is that I got to find myself one of those pump sprayers that can handle the mixture.