You put the block in the front diff. Locks the front end and will give you more acceleration out of the corners. It will make the car understeer more than a gear diff. You can use different weight oils to mess with how the car turns in. I think I have 150k oil in the front diff of one off my tt02's and it's a good mix between the two. The 150k leaks out a bit so I wouldn't go any thinner than that.