I am running steel drives as well. The shaft itself is not the problem but the yoke. The yoke is the part that attaches to the tranny. You need the revo style with 2 pins sticking out twards the tranny. These pins hold the new type brake disk. Your current setup has that blue aluminum hex on the yoke for the brake disk. This will not work on the newer grey 4908 tranny.The bolt pattern is even different. As far as I know traxxas has the new yoke for use with your traxxas center cvd's on backorder. First i made my own plastic driveline and installed pins to hold the brake disk but it was a weak setup. I just bought a new 4908 revo spec plastic driveline. It has held up to my axial .28 for 3 gallons now. I will eventually get the right front steel driveline but it works for now. This tranny is pretty strong. Good luck.
see attachment if not in post. pic is a little blurry. I can take a better one in the am if needed.