What gears to run?

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BillyBBad

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68 FB Cuda with 360/727 runs 13.27 on a good day.
What gears would you guys run?
It sees little to no street use and if and when it does it's at low speeds.
4.10's
4.30's
4.56's
 
Geez, always asking questions :tongue: Just kidding, sorry i never said did i?

Right now 5700 rpm is top (if i remember right)
tires will be 27/9.00x15 slicks
gear i have now is unknown, I never did check. I know when i changed from the 8 1/4 to the 8 3/4 it dropped in time.
 
What is the current tire size? How high can you spin the motor and still make power. Where does the car like to shift now? I am not the biggest mopar rear end guy but I am sure you lost some speed from the 8 3/4 having heavyer parts. I am guessing your MPH is around 102 and if it is your current gear with a 25 to 27 inch tire is around 3.80 to 4.10. But I could use a little more info.
 
id say 4.10s cuz like my car your gonna run out of motor with the 56's now i hav bigger tires so thatll help me out a bit now she shouldnt run out of steam! go with the 4.10" :thumleft:
 
MidTexCuda said:
What is the current tire size? How high can you spin the motor and still make power. Where does the car like to shift now? I am not the biggest mopar rear end guy but I am sure you lost some speed from the 8 3/4 having heavyer parts. I am guessing your MPH is around 102 and if it is your current gear with a 25 to 27 inch tire is around 3.80 to 4.10. But I could use a little more info.
Click to expand...

Good call, I trip the lights at 101 mph. The current tire size is a 245/60x14. When i go out to the garage later i'll get the height of the tire then.
I can spin the motor to 6 grand but thats a little tight so i backed it down to 5700 and seems to like it there too.

I have people telling 4.56's and i have seen some bad a$$ times from 4.30's as well.
Im sniffing around for low 12's out of this thing.
 
If you are going through the traps at 5700 and 5700 is about the max, the gear you have in the car now is the limit. OK did some work on your gear tire combo. Not 100% but I think I have it nailed down. With your curent tire size, and crossing the traps at 5700 your gear is around 3.92 to 3.98. If you go from you 26inch tall tire to a slick 27+ that might grow .05 a 4.10 gear will give you the same results as your current tire and gear combo. If you go bigger than a 4.10 gear on either tire you will only pick up RPM and not MPH. I think you will se bigger gains from the current gear and a taller tire. If you can reach 5700 with the new 27in tires through the traps you will see about 4 more MPH at the traps. The 4.10 gear or bigger will let you get going quicker but if you are RPMing out at the trap. You will need to drop weight of find another way to make the car quicker. Gears can only do so much before they work against you. I say Put the new tires on and run the car. Find out what your trap RPM is and test you shift points. I would say your trap RPM sould be about 100 to 300 above your shift RPM. If you are close that through traps with the new tires ( with in 250 RPM) ie if your new tires net you 5500 trought the traps You cant gear up it will make you run out of gear to fast. In other words makeing up the extra 200 to 250 RPM through tweeking or weight reduction will net you the faster ET and MPH where the gear will not. I hope I did OK explaining this if not I will try again.
 
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