This seems to be a common problem with the riding mower. I did find a solution, hopefully this helps. Although this particular mower is a craftsman I've noticed the problems with quite a few different brands and models. Not sure if your part is available at Sears if not you could try:

https://www.ereplacementparts.com/husqvarna-parts-c-114486.html?source=gaws&gclid=CjwKCAjw44jrBRAHEiwAZ9igKH6txKG1RnZgyC2KYRvT8INVVv8COou5_f9h9ijGIRyq3oSZP935GxoCasIQAvD_BwE

I am including the link and a pic as well of the online solution below.


Online Solution
If the axle has come out of the transaxle, the transaxle has to be taken apart to repair. The reason is the axles are held in the transaxle with clips on the inside. Once you have the transaxle apart,look for the clips. If they are broken, be sure to find all of the pieces. If you leave any thing loose inside it could find its way into the gears and cause a failure. If you need to order the clips, you can do so from our parts website: Sears Parts Direct

https://www.shopyourway.com/questions/1126889