What should I do?

[D17KDB]

First, I'm not trying to be a douche. If you already have the box off and open you can calculate your final drive by counting the teeth on the gears. There are many websites that have the required formulas to figure out your final drive/gear ratio based off of this. A quick way to verify this would be to count your teeth and compare the numbers against someone who knows for sure they have a 4.7FD, math wouldn't be involved then.

This would let you know for certain, without a doubt, what your final drive is. Math doesn't lie.

Other than that, there may be a serial number some where but chances are you wont be able to see it without taking it all apart.

The gearbox is on the car at the moment. It was more something to change over winter. The car has been all back together since about march.

 

[oifovo]

What rpm does it sit at when doing 70mph?

You must check what RPM it sits at when you are in 3rd, not just in any gear! If it is a 100% stock 98 spec S80 then the 4th & 5th will be longer, so when combined with 4.7 fd the revs will be pretty much the same as with standard 4.4 S4C. That's the one thing I don't like on the 98 spec S80 - the massive gap between 3rd & 4th - if I get one I will put in the 4th and 5th from my own S4C box...

 

[eg6 flex]

^ that's what I have in my S80

Oh and a Mugen diff

 

[ek9mike]

you will notice a big difference with the s9b gearbox. I had the standard s4c box in my car till i destroyed the final drive, then i put in the s9b gearbox and to be honest the gearing really is pretty tall. Im thinking of either going for another s4c box or maybe an s80 with the 4.4 fd

 

[D17KDB]

So would i be better keeping the S80 and just changing the final drive?

 

[Nuno@Camtec]

So would i be better keeping the S80 and just changing the final drive?

s9b mate.

torsen diff is more than enough for the job, and the 4.2fd is ideal.

also its relatively hassle free compared to starting changing gears about in your current box.

Nuno.

 

[B18C'R EK]

s9b mate.

torsen diff is more than enough for the job, and the 4.2fd is ideal.

also its relatively hassle free compared to starting changing gears about in your current box.

Nuno.

x2

i have a s9b on my b18 turbo

 

[dhdavectr]

If you have the 4.4 fd in your s80 I'd keep that instead of swapping out to a 4.2

I know the s9b is 4.26 not sure what the 4.4 is exactly to the next number but that's not a huge gap.

If you're running a 4.7 then yes it would be worth it.

If you stick with the 4.4 then maybe think about a taller 1st gear or run boost by gear/revs ?

 

[D17KDB]

s9b mate.

torsen diff is more than enough for the job, and the 4.2fd is ideal.

also its relatively hassle free compared to starting changing gears about in your current box.

Nuno.

cheers and thanks for the advise guy's. Much appreciated

I think my S80 will be coming out and going up for sale very soon

 

[Nuno@Camtec]

cheers and thanks for the advise guy's. Much appreciated

I think my S80 will be coming out and going up for sale very soon

honestly this is the best thing you can do.

Even 4.4Fd's can be a bit short, s9B's are just perfect over all in stock form.

Also cheap to pick up these days.

Nuno.

 

[D17KDB]

honestly this is the best thing you can do.

Even 4.4Fd's can be a bit short, s9B's are just perfect over all in stock form.

Also cheap to pick up these days.

Nuno.

cheers. I already have a s9b lined up. Just need to arrange when i can get the S80 out so i can get it sold.