BAIN

iTrader: (5)

I posted this in the gears and axles section, but I figured I would get more help in here with the drag racers

I was just wondering if I would pick up any time going from 3.73's to a 4.10 gear in my car? It's a 2000 A4 cam only car with a T-Rex and a TCI 4400 with the shift points set to 6700. I took it to the track and it doesn't seem to pick up untill after the 1/8th compared to my previous cam. It picked up .02 and 1.4mph in the 1/8th, but in the 1/4 it picked up .10 and 2mph. According to an online gear calculator I'm crossing the 1/8th- 96mph @ 4650rpm and the 1/4- 120mph @ 5800rpm. Could those numbers be right? I don't think so because my shift extension is close to 5900-6000rpm after the shift.

I guess I just need some positive feedback before I put the 4.10's in or should I leave the gears and get a larger stall?

Thanks in advance guys.

rebersole2

I run a little different combo than you (carbed, na LT1/ TH350 in a 86 coupe). I will tell you that I run a 28x9x15 MT slick at 16 psi, a 4.10 gear and a 4000 TCI stall converter. I pull mid 1.60 60' times and I shift at 6200 rpm's and I cross the line at 6100- 6200 rpm's. I use to run 4.56 gears in another combo. It was one heck of a launch (1.48- 1.52 60' times), but man was it rough running the quarter on a short tire. rpm's were in the low to mid 7000's.

BAIN

iTrader: (5)

So would the 4.10's help any over the 3.73's

SMOKIN01TA

iTrader: (10)

well A. you are not shifting high enough, if you scared to shift higher put rod bolts in it but that cam needs to be reved to 7100-7150rpms for shift points, and yea, you most definatly need more gear and would garunteed pick up from it, if you are only crossing at 5800 rpms you are leaving alot on the table, you need to be at 7k+ going across the traps. so if you are running 3.73, im thinking more along the lines of a 4.30 gear, a 4.10 wont change your rpms enough using the same tire. if you want to optimize that setup use atleast a 28" tire and gear accordingly to get 7k at the traps,

BAIN

iTrader: (5)

Thanks. I was hoping some of you faster cam only guys would help me out.

As for 4.30's, I would love to go that big, but it's still my daily for now. I think I deal with the 4.10's though.

PewterZ28

iTrader: (1)

What he said. I would think you can pick up around .15 by choosing a tire and gear combo that will have you crossing the traps at the end of your powerband. That is one of the most important elements of the 1/4 mile. Sure, your top speed might only be 122 mph but at least you get there in a hurry.

SMOKIN01TA

iTrader: (10)

i would expect him to gain a good 3-4 tenths in et if he shifted at 7100+ and crossed at that also, i lost 3-4 tenths running these 4.10 over my 4.56 staying with the same tires just because i bogged out the hole and only crosse half way through 4th gear. im glad it was only temporary

BAIN

iTrader: (5)

Well I think I have made up my mind

I'm going with 4.30's on 26" drag and shifting at 7000-7100. I'm also stepping up in converter to a 4800 since that is where most of the dyno's of the T-Rex I have seen peak in torque.

How does that sound guys?

SMOKIN01TA

iTrader: (10)

sounds great, my only suggestion is to get the people you getting the converter from to tell you what mph that combo is good for at 7000 in 3rd gear with the slipage factored in, id hate to see you on the limiter before you reach the traps. you need to be able to go id say atleast 125 mph.

BAIN

iTrader: (5)

Good point. Maybe I will try the 4400 I already have with the 4.30's first and see how it goes.

PewterZ28

iTrader: (1)

I think you are going to run out of RPM. 4.30's with 26" tires seems to small, I would think you are going to at least need 28" tires with those gears unless you are locking the converter. I have 4.10 gears with 27" QTP's and I plan on crossing the traps around 6800 and 124 mph.

BAIN

iTrader: (5)

Grrrrrrr. I thought I had it figured out!!!

26" tires, 4.30's, 4800 stall and shifting at 7000-7100 and now looks like none of those things are going to help me get into the tens.

I already have 3.73's so I figured the 4.10 wouldn't help out that much. That's why I planned on the 4.30's. I have a 4400 and the shift extension is a little low 5800-5900rpm and it doesn't hit right at peak torque 4800 by 6 speed graphs. That's why I was going to a 4800 stall with a shift extension of 6200-6300rpm. I really appreciate the help you guys have given me. I'm to the point of banging my head against the wall trying to figue out what would be the best combo for me to get in the 10's.

BADFNZ

iTrader: (19)

Due to the slippage of larger stalls, you won't notice much of a difference in RPM going through the traps. I'd just raise the shift points a couple hundred RPM and see where that gets you. It'll help the shift extension issue too.

PewterZ28

iTrader: (1)

Go with either 4.10 gears and 27" tires or 4.30 gears and 28" tires. I would choose the latter if I were you.

BAIN

iTrader: (5)

I tried raising the shiftpoints from 6700 to 7100rpm and the mph shiftpoints up +4 this past weekend on an 1/8 mile track. There was no difference in times or mph with my current setup (4400, and 3.73's)

68maro

you'll be in good shape with the 26" tall tire and a 4.30, you should be able to hit 130 with a 7200 limiter if you trap 124-125 you'll go across between 6900-7000. just input your different tire and gear combos hear and you'll get a close idea.
http://www.speedworldmotorplex.com/calc.htm

SUX2BU

iTrader: (14)

only prob with that is in an auto you have to factor in converter slipage.

BAIN

iTrader: (5)

How much would converter slippage factor into the rpm's?

FACE

I'd do 4.10's with a 26" tire to be safe. That way, if you run out of gear, you can just upgrade to a 27" or 28" tire.

SUX2BU

iTrader: (14)

depends on the converter, my friend tried out this converter for me and his 6800 shift light was comin on WAY before the end of the 1/8 mile track with 26" tires and 4.56 rear gears at about 98 mph.
I'm going with 4.10's and a 4600 and crossing my fingers that i can make it down the 1/4 with 26" tires. it will be close.(SI looking to trap right under 120)