You really wont notice the difference while driving between a 3.73 or 3.90 or a 3.90 to 4.10.
Just be sure that your tires are 30" tall like I had guessed. I used a tire size calculator in my Tunercats 2 tuning software to estimate your tire height using teh tire sizes. The most accurate way to determine your tire height is to put a mark on the ground right in the middle of where your tire squishes on teh pavement, then roll the truck backwards or forwards just enough to rotate the tire EXACTLY 1 revolution. Then make another mark on the ground. Measure teh distance between the 2 marks. Then use teh equation C=Pi x D
or
C= 2Pi x R
C=Circumference (distance around the tire)
D=Diameter (distance from 1 tread surface to the opposite tread surface)
R=Radius (half of the diameter-center of rim to edge of tread surface)
Pi=3.14159265 (the ratio of every circles diamter and circumference, every circles circumference is 3.14159265 its diameter)
Lets say you get a measurement of 90" between the 2 marks, 90=3.14159265x D
90=3.14159265xD
90/3.14159265=D
28.65=D
Diameter=28.65"
This is the most accurate way of determining precise tire height, even the tire manufacturers arent as accurate when the tire is installed on your rims and on your truck.
If you really want out of the hole performance, a good performance torque converter would be of more benefit. With a stock torque converter, you will always have to accelerate through those rpms at which torque is NOT strong. If you go to a lower gear, like 3.08 to 3.90 or 4.10, you will still be accelerating through that "dead spot" although with the lower gearing makes teh amount of time spent in athat "dead spot" markedly less.
A performance torque converter allows your engine to simply "bypass" that "deadspot" altogether and get right into your engines torque and then power bands.
Not only will you bypass the low torque rpms from a stop, the performance TC will allow you to stay in your pwoerband during WOT upshifts. WHile this was more of an issue with teh 4 speed autos because of their large gear spacing between 1st and 2nd gears, if you look at the 6l80e and 6l90e, the 1st and 2nd gears have an even larger split in ratios.
700r4/4l60/4l60e/65e/70e
1st 3.06
2nd 1.63:1
3rd 1:1
OD 0.70:1
Gear ratio spacing equals Current gear minus gear being shiuft3ed into
3.06-1.63=1.43 gear spacing between 1st and 2nd gear
1.63-1=0.63 spacing between 2nd and 3rd.
6l80e/90e
1st 4.03:1
2nd 2.364:1
3rd 1.532:1
4th 1.152:1
5th 0.852:1
6th 0.667:1
4.03-2.364=1.666 gear spacing between 1st and 2nd
2.364-1.532=0.832 spacing between 2nd and 3rd gear
1.532-1.152=0.38 spacing between 3rd and 4th
As you can see, that when you compare teh gear ratio psacing between the 2 transmissions, you can see that there is a marked increase in the amount
of gear spacing in the 6l80e vs the 4l60e series of transmissions.
In my experience, there is substantial acceleration gains to be had when making teh ratio spreads closer than stock in teh 60e. One way to do accomplish a similar effect, is to install a higher stall TC. I did this in my truck and when I shifted from 1st to 2nd at 5500rpm with teh stock TC, the tach would read at around 3200rpm after the WOT upshift to 2nd was accomplished, then after installing a Vortec 4.3 V6 TC behind my L31 Vortec 350, performaing the same 1-2 WOT upshift with a 5500rpm shiftpoint, the resultant rpm on thetach was 3700-3800rpm.
With the stock TC the trans would shift into 2nd and there was always a brief period where acceleration was poor as teh engine struggled to recover its torque as the engine revs up in 2nd gear. AFter teh TC swap, instead of this acceleration "bog" 2nd gear would grab and teh engine/truck simply accelerated. It was abig difference, it totally changed the toqrue recover during WOT upshifts, along with allowing me to have a stall spedd of 2800rpm vs the stock TC stall speed of about 1800rpm. Meaning atht when I launched form a dead stop at WOT, as soon as I punched teh throttle the tach would flash to 2800rpm as teh truck left teh line, whereas with teh stock V8 TC, the tach would read about 1800rpm. Having slicks on at the time allowed for a dead hook, so comparing stall speeds was much easier than trying to do so with street tires that would simply lose traction during a WOT punch.
Even with ypur stock 3.08 gearing, your overall 1st gear final drive ratio is 12.41:1, or your engine turns 12.4 times for every revolution of your tires.(assuming zero trans/tire slippage).
The soggy low rpm torque is the design of the engine, coupled with the ECM trying to protect the driveline (Torque Management and all teh TM'like tables in the PCM/TCM).
In all honesty if your lazy low rpm launches are your main issue, a quality performance torque converter will allow you to accelerate in a much more agressive manner that even going from 3.08 to 4.10 gears will.
I went from 3.08 gears to a 4.10 gear while at the same time installing a locker in teh rear and when I punched it from a stop, I was surprised how little theSOTP(seat of teh pants) acceleration had changed. I thought it was going to be out of control tail wagging fun from a stop, butr while thedrag numbers were improved I have to admit there was some disppointment there. My truck already has strong torque, so having too much gear and torque converter can just as easily hurt acceleration, but a truck like yours with an engine that makes much more power at mid-high rpms, a middle of the road gear change, accom[panied with a good torque converter swap, can significantly improve your current "waiting for teh p2woer to come on" feeling, to an immediate
ut you in your seat" feeling from a dead stop to whenever you choose to let off the throttle.
If you go with a quality torque converter, your requirement for rear gearing to aid acceleration will be decreased. Because of the transmissions very short 1st gear of 4.03:1 you could get away with a 3.42 or 3.73 and have much better acceleration than a stock TC with a 4.30 gear. You might want to stay a bit more conservative on teh rear gear with a performance torque converter just so you will be able to retain traction. This will give you better fuel economy when on the freeway with the higher gear as compared to the lower 4.10 or 4.30 gear. Then if you ever had to tow anything on the heavier side down the freeway, you could simply select 5th gear instead of stressing the trans in 5th gear with a load.
Since these modern performance torque converters and transmissions have a lockup Torque Converter Clucth, you can have whatever torque converter stall speed you wish, then when the TCC locks, you will retain your cruise rpm just like a stock TC. Be cautioned though, that a TC with too much stall speed will creat more heat when the TC clutch is not engaged than a stock unlocked TC.
A good quality performance torque converter will yield you better acceleration gains than your headers/programmer and gearing combined.
Sorry for the book, but this deserved adequate explaination. Before you pick a gear, be sure to find out teh exact diameter of the tires you are or will be running.
peace
Hog
