[Luke758]

I’m looking to swap the 3.5 diff in my 3.8 to the 3.9 diff from the 2.0t, and I know the bk1 3.8 and 2.0 diffs are interchangeable, but I don’t know if the same is true for the bk1 3.8 diff and the bk2 2.0t diff. I’m pretty sure I saw a thread on the full breakdown of the BK1 vs BK2, but I can’t find it. Does anyone know if the diff would be a direct bolt on? If not, would the bk2 gears fit in a bk1 case? Thanks

 

[Pchelka]

You may need axels as BK 1 has a Spline IN to diff axel while bk2 have a 'cup' design. better for servicing in my opinion. just google the pictures and you will understand whats the diffrence

 

[AKGC]

IIRC they are the same.
If you have a bk1 and want to put in a bk2 diff, you just have to remove the cups (or replace the half shafts with ones for a bk2)
If bk2 with a bk1 diff, you have to either source the bk2 cups, or replace with bk1 half shafts.
I haven't done it myself, so I could be wrong. Can someone verify?

It's easier to replace the cup style half shafts, without having to dismantle much of the suspension (in general)... but you have a slight bit more rotating mass.