my friend changed his rear diff in his s2k to 4.77 and he also says #1 mod ever... i think he actually said it "best 888$ ive ever spent"

 

I think most of those who claim that it is the "best mod ever" are unknowingly proving this phenomenon which I previously mentioned:

Just my O...

 

duely noted...but i believe that it does accelerate faster to some degree, but just not as fast as it feels

 

I have to agree with NSXstacy. I can definately see how changing the overall gearing could be a help or hinderance depending on the given track. In fact even in an autocross situation it can be an advantage or diasdvantage to have a lower fd depending on the course. Some courses will be a little too open for the lower gearing and you will want to shift up into third soon before slowing for a corner, but would probably lose time shifting up to 3rd and then back down to 2nd a second or two later. Whereas with the stock gearing you can carry that extra speed in 2nd into the corner without having to upshift and then quickly downshift. I've come to find there are no modifications with only upside, they all have some downside. Having said that i think the 4.785 fd is an excellent mod for myself and in general works quite well for most applications. I also believe there's a reason that fd came in the Japanese itr's.