Did you swapped the right and left axles from one side to the other? If you did , DON"T ever do that again
If not something is not correct on your deal
Usually the left axle fails first due to the load on the driver side compared to the passenger side
Please take the time to check the tranny for interior damage
I have a SS/AH all out drag race 727 on the bench that ended up doing what yours is doing now, it failed when I broke a rear end in my old pump gas Duster. I haven't taken it apart but it would move okay under light throttle in first gear but not under half to WOT
I'll take it apart soon and fix it as it will be going into my new back half drag car