My friend and I were arguing, I think the stock diff is a 2 way while my friend says viscous, or helical. The car snaps from understeer to oversteer, classic 2 way behavior. Can anyone back me up or prove me wrong? Thanks in advance.

 

Your friend doesn't know very much, he's arguing a totally different point. Fb's use a clutch type limited slip. I'm not sure if its a 2 way diff or not, but snapping from under to oversteer wouldn't tell you much reguarding that in this case. Ever drive a FB with an open diff? still snaps from from under to oversteer. My car is a S, and while I've swapped in a GSL rear end I didn't think it was that much of an improvement, its better sure, but not hugely different. Oh and I agree, drift should stay underground, the minute D1 came here drifing died a little, now every initial D (which is a good anime, but not accurate) wannabe thinks he can drift. but I digress....

 

it's a viscous type since it mainly relies on the diff. fluid for the clutch pack to lock

 

no it isn't, it relies purely on the preload put on the clutch plates inside it. Viscious diffs have several plates spaced slightly apart, as they spin in opposite directions the goo like fluid thats in there heats up and stiffens creating pressure on the plates and thus keeping one wheel from spinning like crazy. They are good if you want a smooth diff, but bad cause they are slow(er) to react and if you have a ton of power they won't work much at all from a straight stand still

 

He's exactly right. All the FB uses is preloaded clutch disks. You need the fluid in there to lube the gears, not the clutch packs. Also, you ever make a tight turn (like a U turn) and felt your car jolting? That's the LSD slipping.