Blown Alcohol on 10.5's first gear ratio???

BAE hemi supercharged 2300hp/3200lbs converter driven 2 speed on 10.5's.......What first gear and rear gear you running? I started with a 1.40 first gear, final ratio in 1st gear is 5.74 with a 4.10 rear gear, wanna try a 1.57 first gear that will make it 6.44 in 1st gear . Anybody running something similar? I run 1/4 mile mostly- been 4.55 to the 1/8 and 7.00 1/4. I'm thinking the 1.57 first gear will get the weight moving quicker off the start as long as I can hook it.

 

10.5

You are in the ball park... What is the weght of your truck... keep putting more untill you cant hook it or over-rev at finish line.

 

We had all the ratio in the trans last year. This year we're swapping it...putting ratio in the rear end and lower in the trans (actually going from 3 sp to 2 sp). Not sure on why makes so much difference, but too many people have made gains by switching it. We had a 7.74 1st gear ratio w/ 1.13 60'. Now we're looking at going w/ a 6.73 first gear. Only problem I see w/ your deal is that's a huge drop from 1.57 to 1:1. Might loose boost? or possibly traction? Just throwing it out there.

Josh

 

ratio

6.50 ratio is average for a promod with 34.5 tire. If you are making good wheelspeed and pulling out some timing I wouldn't go with a lower first gear.
We ran a 2900 lb roots glide car with a 1.80 low and 4.56. It went 4.40's but we had to dump half the timing on the hit to soften it.It could have pulled a lot higher first gear and wouldn't have the huge drop at the shift.
You'll find a lot of old school clutch guys that will still want low first gears but huge gains in automatic cars have come from trying new things in low gear.
You want the converter to stay slipping/multiplying as long as possible.Once it locks up you're no faster than a clutch.
We're switching to a 1.31 low with a 5.00 rear 2 spd for 1/8th mile. I hoped to hit it with more timing on the start but now we bought a screw so we'll probably wish we had a 1.25 ratio in it.

 

I mentioned it in the post its 3200 a little heavy thats why I thought a higher numerical 1st gear would get the weight moving... I'm running mostly 1/4 mile and as we all know most of your et is gained in the first 200 feet or so.

 

With the 1.40 gear we are pulling out 12 degrees and we had it all back in at 1.00 second. we were gradually still bringing it in sooner and it was taking it without spinning the tires. So if it tries to spin the tires with the 1.57 I still have some timing to play with. Its a heavy truck I think the mechanical advantage of the 1.57 will allow it to accelerate faster earlier in the run and as a bounces make boost quicker.

 

Yes it will probably drop a few pounds at the shift but I think the quicker accelerating 1.57 will net me more ET overall.

 

ratio

the cheaper/easier way to test your theory is to throw a 4.30 or 4.56 in the back. You need to turn 9000 through the lights. At 4.55 in the 1/8th it can't be spinning very fast.
If you want to accellerate faster throw the timing at it until it spins or shakes.
I don't have 10.5 tire experience but i've watched it closely and I know guys were launching in high gear even at heavy weights when they first got the screw cars flying.

 

gear

1.31 with a 5.00 gear or a 1.40 with a 4.71-5.00 gear works.