When I had mine done I went the other way. Stock is 4.1 lots of people go to 4.5 or higher but I went to 3.9s. Take a stock car and boost it by like 40 to 50%. Think it will accelerate faster? Duh. Which means you are doing the first and second gear shifts much closer together. Couple that with going with 4.5s and shit you might not even need 1St anymore, lol. you see my point. I do a little autocross and hardly ever get out of second gear. Going to a 3.9 is a 5% change. You will never notice the difference with 40% more HP. And you spend more time in first and second(notice most here), have better gas milage, less RPM and drone at highway cruise, and you have a higher top end. If you are not building the car to drag race than I think it is a no brainer to go to 3.9s if your boosted and your are going to do PuddyMod and if you are not drag racer(and it sounds like your not).

 

Maybe you miss reread my initial post. I had 4.56 gears and sold them. Don't think many put such low gears when making 450whp most go the route you did. Talked to my tuner and he believes 4.10 will work best. really no sense of putting gears in the diff if I don't plan to stick with an s2000 diff later down the road. Also not concerned with gas mileage since it's not my daily.

 

The stock diff works when driven correctly. For all motor guys, they work better but they still break diffs while road racing. I was at 630whp for 3 years and countless 700hp pulls on the dyno and the diff showed no signs of fatigue. Rev match, know how to shift, don't shock the drivetrain and you'll be fine. I made one mistake with my last diff and it split the diff in half (downshift to 4th).

If you're worried about it, buy a spare or throw in a Ford 8.8

 

Nicely said ^! Thats the plan.

 

Ran my car boosted for few thousands of miles. Stock diff (93k) finally gave out after 30 passes and still went 11.40

 

Still, going WOT is not what kills these things. It's ALL in the driving style. Don't launch the car, and don't bang gears, esp the 1-2 and 2-3 change.
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+1

Also, leave the CDV alone.........

 

He doesn't have one. He has a Ap1.

 

Do what I'm doing.

Buy http://www.weirperformance.com/solid...pacerkits.html

Then take a bearing cap off and have a machine shop build you one out of something stronger.

Send it, the ring and pinion, and the sleeve to be cryo treated. Get it back, install it all. I reccomend buying a new ping and pinion just in case yours is iffy lol.

I was at 581rwhp on 93+meth on f20, now it's a f22 with e85. Waiting to get tuned. Will still be on stock diff and trans, low boost in 1st and second, and add 5 more or so in 3rd, then let it eat from there.. lol

 

So your rebuilding your stock diff? what kinda of price range should I expect?

Diff Blown!
2007 s2k
CTSC 300whp
59k miles (bought it with 48k)
Its my DD and often do pulls to redline... few hrs on a go-kart track this month. No launches really.. I was taking a 90* corner at about 50mph when i felt a big clunk as I was exiting... gring grind grind. Towed it home and drained the oil and metal chunks out of my diff

 

I meant in general, but if he's really concerned he could easily put one In, or swap with an AP2 etc