Is my tranny or differential broke? Options

[HardHead93]

The car has been leaking gear oil. I thought it was an axle seal so I took it to my local shop because they installed the original seal and would warranty it. Come to find out it is not the seal. The axle has some serious in and out play in it. When it moves out gear oil leaks out. The shop has tried 2 other brand new axles and the problem is the same. The last axle would not click and lock in. I have a helical LSD in an S54 transmission and I am running a Gen 4 3sgte tuned for 340 hp on E85. I track the car so it gets beat on pretty hard. The shop is having a hard time getting a good part number because the original part number is discontinued but superseded by another. One axle came from OReilly's and the other came from AutoZone. Is the tranny or the differential broke or am I not getting the right axle? Has anyone else had this problem?

[Bitter]

I want to say the manual and auto use a different axle and that the length of the part that inserts into the trans is the difference, with one being longer or shorter than the other. I'm assuming it's the driver side because they're the same auto or manual on the right side it seems.
Automatic
https://www.rockauto.com/info/570/TO-8145__ra_p.jpg

Manual
https://www.rockauto.com/info/570/TO-8106__ra_p.jpg

What often happens is that cores aren't sorted/boxed right when they go back for refurb so you'll get parts randomly boxed wrong that way. Might be worth checking inside the diff with a flashlight to make sure nothing has gone wrong, how did the old axle that came out look? Is there excessive up down play in the bushing the axle rides on?

This post has been edited by Bitter: Apr 25, 2019 - 7:59 PM