Changing rear end ratio?
 

The next thing I want to do, is change the rear end. I want either a 4.3, or I have even seen something like a 4.88.

If I stay all N/A, large street port on it's way, what would be the best to have to improve 0 to 100, maybe top at 125 or 130? Less wouldn't bother me. I am looking for acceleration.

Also, where is the best place / lowest price going to be? I have seen a 4.3 for sale at mazdatrix. I will probably buy all the other stuff for the rear since I will have it apart, why not rebuild most of it.

I might just wait and change the LSD too. I am looking at spending about $1.5k for everything. That expecting too little?

Thanks.

Mods in sig.

4.3 is found in the GTUs, gear is available from Mazda and any place selling OEM parts. There is a 4.88 and 5.12 on the market but very hard to find. They are custom built by meshing a 1st gen pinion with one from a 2nd gen and usually found in ITS or EP race cars. These are expensive with the diffs going for around $2500 built (w/LSD) and $1500 used, assuming you can find for sale. I've never seen just the R&P go up for sale, it's usually the entire diff. As far as getting one? Don't know any for sale but there is someone who claims they can make the 4.88 or 5.12, you just provide both pinion gears - (around $500+ IIRC for the 1st gen pinion, 2nd gen easy to come by).

Even with the 5.12, you still won't be topping out anywhere near 130. For example, with the 5.77 (hypothetical) R&P, you'd be topping out at 153, still higher than what a streetported NA can give you.

This was posted somewhere else by someone with Speedsource....

If you are running a 5.12 and GTU fifth (.76) you will run 122 @7000, 131 @ 7500, and 140 @ 8000. You will run out of motor before you run out of gear. This is with a 225/45/15 hoosier. Just for reference at 8000 you are :

1 30 mph
2 53 mph
3 77 mph
4 106 mph
5 140 mph

I'm using 9200 as the max rpm and .711 5th gear, for clarification.

SCCAITS, you mean GTUs, right?

Yes. I had just copied the quote from the other site and OP wrote GTU when it is/he meant GTUs

Hmmm, would changing from 4.1 to 4.3 make a large difference? Noticeable improvement from 0-60? 0-100? Or would i need to go higher?

I'll keep looking around. I want acceleration. I have done a lot to the motor, but i want to stay N/A and improve the acceleration.

Thanks for the responses guys.

It's a slight improvement, but it's noticeable. I have two cars, one with a 4.1 and one with a 4.3, but the car with a 4.3 is also tuned better.

Just buy a GTUs ring and pinion. Thats a 4.3 ratio.

hmmm i might have to find a gtu ring and pinion. I'm running the 3.90 from an auto in my s4 na

GTUs and GTU have two different R&P gears......

sorry meant GTUs, the gtu is just a 4.10 like all fc's besides autos right?

yup