7:31 R&P torque capability or 8:31 gearing issue
 

I’d like some advice on preparing my transmission to handle my 3.6 VRam swap. I currently have an 80’s 915 in the car with a 7:31 ring and pinion and swapped 3, 4, 5th gears in the car. For the autocross in particular I like where 2nd gear is with the planned 7500 rpm motor- the limiter would hit at 72 mph, which sounds about perfect. The question is will I (or maybe how fast will I) break it between the autocross and the track?

The other option would be to put the 8:31 I have on the shelf in, but even with the smallest reasonable 16" or 17" DOT competition tires I see I’ll be geared 10% higher, and so be putting down 10% less torque through the speed range I'm worried about. I guess the right thing to do would be to swap in the 8:31 and then do a new 2, 3, 4 and 5, but that sounds awfully expensive compared to using what I have...?

So any thoughts on how long the 7:31 would last? Is there a good way to extend this? Am I missing a better option?

I found the following good threads with Haden's advice (wevo) in particular on the subject that indicate it’s not a “good thing” to use the 7:31, but is there a reasonable alternative?

http://forums.pelicanparts.com/showthread.php?s=&threadid=151877&highlight=731+to rque+wevoid

http://forums.pelicanparts.com/showthread.php?s=&threadid=118829&highlight=731+to rque+wevoid

p.s- I’m posting this from somewhere over the atlantic in a plane on the way to Germany- ‘bout time they got wireless internet into these things. Nice.