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#1
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Thanks for Deciphering My last post on the Torsion Bars what a mess! Anyways all the replies really helped alot. Onto my next problem probably my biggest one right now. Last season I only made the last two races and I found out that I have a gearing problem (first let me review my vitals 76 Charger Bomber/Streetstock 400cid 3400 lb weight rule 1/4 mile semi banked asphalt)
I found that if ran in 1st gear (727) I was turning 6100-6200 maxium the 400 was not very happy with these numbers so I had to run in 2nd where I was only turning 3100-3200 maximum I couldn't stay with the pack on a restart or coming out of a corner. So here's my problem the car now has 3.23 gears in it I have a parts car which has 2.76 gears if I swap the 2.76 rear end in would that be enough of a drop in rpm to run in 1st gear? Or , Track rules state I have to run 70 or 75 series steet tires last year I ran what every one else did 15" 235 70's right side and 225 70's left side but the rules do allow to use 14" rubber if you want so if I dropped to 14" rubber would that raise the rpms up enough to run decent in 2nd? I know thes solutions are not ven close to ideal but I dont have much cash to invest right know so a low buck solution is my only way right now. Thanks a million for all the help. |
#2
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I'll take a stab at this one. I'd say, yes, the 2.76 gears will get you closer to where you want to be, given you keep the same size tires on the back. I've seen plenty of 727's and 904's ran in first gear and as long as they've got a good tranny cooler they do fine.
Your final gear was 7.91 with the 3.23 gears (3.23 times 2.45, which is a torqueflight's ratio in 1st). If you go to the 2.76 gear your final will be 6.76, which is a pretty big drop. Compare that to the 4.68 final you were running in 2nd gear (1.45 times 3.23). A couple of guys I know in our bomber class opt for the 2.94 gears, which gives them a final of 7.20. Different track, I know, but if the 6.76 is a little too low (numberically) you could go to that. |
#3
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I figured your est. rpm's with the 2.76 gear in 1st. It would be about 5300 rpm's. Try this site to compute your own.
http://www.idavette.net/tech/ratioc.htm p.s. 225/70 tires have a diameter of 27.4 inches. |
#4
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A tip that I learned is that for every inch in circumference is a difference of 100 rpm so if you go to a one inch smaller tire you will turn 100 more rpms. I would get a thin tape measure made for checking tires and start measuring tires and add and subtract your rpm that you are currently running. I call it cheap gears and it works.
I ran 410 gears with an 82 inch tire (245 60 series) with a 904 in second (1.54) (6.30 final) on a quarter mile track and it works pretty good |
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