I think you mean Y1 and Y2.

The only difference in between them box's are Final Drive and the Y1 depending on the donor may have had a LSD.

Easy way to tell if LSD came in your box it will be stamped.

"Determining whether or not a transmission has LSD is very simple, just look into the differential and see if its opened or closed. For those not familiar with this, you'll either see a set of gears that form a closed cylinder, or you'll see an open differential with a bar splitting the middle."