rear gearing help

[scotto]

So I'm building up a sr20det with 5 speed, but using a Ford 8.8 irs. What would be a good gear to put in as I'm running a 205/55r15 tire and the rear comes stock with a 3.07:1 gear ring. I'm just guessing that would be way off as all that I've read so far has around a 3.87 or so for a stock sr set-up.

[Mikester]

Standard gearset for most S13's is 4.08:1... Others came w/4.36:1. Not sure what you want to know.

[scotto]

I wanted to know where to start and what would work best with my tire size. I knew that 3.07 was way too small to run on highway.

[godsmack]

3.07 is actually for more top speed. The 4. whatever will give you better acceleration but limit your top speed. And I've never heard of a 8.8 IRS. Are you using an actual full 8.8 rear out of say a mustang? If so if I was in your shoes I'd get the 3.73 r&p gears. With the sr it would give decent acceleration and you would be at around 2,000rpm's in 5th gear running 55mph or so.

[Kingtal0n]

I agree that a set of richmond 3.73 gears would be a great match, but if you are looking to maximize fuel economy and minimize highway RPM a set of 3.5x would be more ideal.

Yes factory is usually 4.08 or 3.9x, and although this is OEM I do not appreciate the 3,200RPM my engine turns at 85mph using OEM tires.

[scotto]

this is an 8.8 irs from a Lincoln Mark 8, nice aluminum housing and quite a bit lighter than the thunderbird units but it uses any of the stock 8.8 rings. They came with a 3.07 from the factory, so I was looking at doing some aftermarket gears and a lsd before everything got too built up.

[godsmack]

I got 3.55's in my fox body but the gearing is different in my tranny verse a sr's. That's why I would recommend the 3.73 unit. But You could always swap later down the road from one to the other to see what you prefer. Swapping the gears in a diff is pretty easy and simple and plus the gears are widely available and decently cheap. If you want to have similar to a 2-way set-up diff I'd get a spool right away. Those are really cheap compared to kaaz and nismo units.

[scotto]

Thanks, now I have to look for a LSD, and get back to work to get some money instead of just spending.

[godsmack]

So whats the mounting like compared to the rs200 for the 8.8? I've been pondering thowing my 5.0 in my 240 and with all the spare stuff I have for the 8.8 I'd be able to make it work really well.

[scotto]

Mine is in a fwd 1988 Sentra, so I had to remove the gas tank, cut a big hole in the floor, and make a subframe for the diff and rear control arms. I'll get some pics up once I find my camera, the kids got ahold of it.