I-shift output shaft

Anyone had transmission output shaft on i-shift repaired/replaced?
I was told I need a transmission back box replaced/repaired because there is too much play on the output shaft, not sure to be honest what is a backbox I assume on the transmission but is it a big job?
Thanks

 

I was told by couple local mechanics that there is about atleast a 1/4 movement when they move drive shaft by hand, I saw it it moves up and down, I called Volvo they say it's normal to move little but not 1/4 of an inch, they said remove drive shaft from transmission and lose carrier bearing, put drive shaft on the ground and there is a plate kind of looks like it that stays on the transmission, they said you should not be able to move that plate, if it moves than u have a problem, well I took down drive shaft and sure enough that plate is moving about same like before 1/4 of an inch, I called Volvo back they said that's a problem, I will post a picture that was sent to me from mechanic at Volvo, that is a plate on a transmission that they said should not be moving

 

It moves up and down left right, and it's turning but that is ok I guess

 

I don't know to be honest, and interestingly there is no oil leak on the seal, yes trany oil is at level