Depends on your tire size.
With 25 inch diameter tires 6500 RPM is only 117 mph.
Personally I wouldn't consider 4.10's under any circumstances, but definatly not with the IRS. There is a slim chance they would be good in a straight axle, since you may be able to launch hard enough to take advantage of the extra torque they provide, but you'd probably need to go with 28 tall tires to get through the traps.
On my 98 I run 26 x 11.5 x 15 et streets. My shift light is set for 6400. When I get a good run 122+ mph it goes on right thru the traps. So at 124-125 where the fast guys with boltons are you are going to be about 6500-6600 with 4.10's and 26" tall tire.
3.90 with a straight axle should be about perfect for D racing with bolt ons. The KB cars would probably need a little less gear. HTH
I can't remember what i crossed the traps at (wasn't looking) but my live axled 03 with 4.10's ran 115.xx (kinda slow?) 12.09. I know it should be MUCH better than that, I guess seat time is what i need....
don't laugh! for the mods, times are high, MPH is slow! I'm working on it though.
2.8 pully, o/r QMP system, and a chip. up next are some subframes, cc plates, a 4 lb lower, JLP(most likely) cold air, and a retune. Oh yea, I guess I'll learn how to drive this car, it's a whole 'nother animal compared to my GT
It is totally accepted that the higher numerical gear you can run, the better. It is like challanging the notion that gravity makes things fall to assert otherwise.
Higher numerical gears can work, obviously, but it is not a given.
Several people have found with '03's that this is especially true. With N/A, turbo and centrifigal blown cars, a big reason they work is that you need to get the car into the power band to get significant torque to the pavement in first gear. The higher numerical ratio rear gear will help bigtime with that.
With a positive displacement blower (Eaton or KB) that is not true. The cars make great torque down low. If you have enough torque to keep whatever tires you are running on the verge of spinning, then you have enough gear.
"Extra" gear, moves all your shifts closer to the starting line . Ever notice how much more a minor f- up on the 1-2 messes up your et than a mess up on the 3-4? That is because you car is going fast on the 3-4 shift so even if you don't quickly get into the next gear, you are still moving down the track. On the 1-2, you aren't moving very fast so any time off the power affects et greatly. That demonstrates how, when you move all three shifts closer to the start line, they become more critical. You really need to shift like a trained mongoose.
On top of that, sometimes with the extra gear on the 1-2, the tires you are runing can't take a super fast shift without breaking loose. Then you are screwed no matter what you do, shift fast, loose et because of spin, or shift easy and lose et because you were off the power in an important section of the track.
Several different cars I have had slowed down when all I did was switch to higher numerical gears. If you decide to go with them, make sure you compare your et's with just the gear change.
JT - Thanks for getting into it, I see what you mean. I think I'm gonna swap the traction lok and 3.55's outta the IRS into the solid rear. This will work okay right? I assume it will it's all 8.8 right???? HELP
JT , You are on the money, Best gear is 3.73 , for the track.
But deponds on the tire ect. 4:10 is too hi, most of the time
Joe you too know you are correct. Take all into consideration,
JUST KEEP THE STOCK GEAR
interesting thoughts! I'm swapping out the spooled rearend soon for something a little more liveable on the street, like a C-Locker! maybe I'll swap in some 3.73s then? I still have some 3.55's as well as 3.27's. Are most KB guys sticking to 3:55's? I may go that route....