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Discussion Starter #1
hello guys, i'm new to this GMC forum and i would like to ask a few questions.
i have a 03' GMC Sierra and i would like to have alot more pulling power to tow my Buick T-Type. i already have a 3" Gibson cat-back and JBA headers. i was thinking about getting a Nelson Tune, K&N Intake, and a Comp Cams Magnum cam. do you guys think these mods are worth getting? if so, how much gain do you think i will have? please respond with your thoughts on this.

thanks,
Cody
03 Sierra
87 T(400hp sleeper)
 

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internet bigot®
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id say get rid of your JBA headers... shorties dont really give much power, switch to long tubes and get some new gears...
 

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Discussion Starter #4
right now i have 3.42's, but i want to keep my gas mileage up.but when i'm on the highway doing 65,it struggles in OD and kicks down to 3rd and pulls.i want alot more low down grunt power and gears would help but this truck is driven every day. i'm probably going to go with some 3.73's down the road, but my question is would all the mods listed above help me out? i mean, the cam alone is probably worth a solid 15hp-15-20Tq right?

thanks,
Cody
03 Sierra
87 T(400hp sleeper)
 

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I'd do 3.90 or 4.10 if towing a lot. With 3.73 and a LT265/75R16 I am at 1600RPM @ 65 MPH. You mentioned a cam, which could hurt mileage depending on what you put it (Obviously you should see power gains).

Think about it this way, if the motor is stuggling at 1500 [email protected] and with 4.10 gears [email protected] you'll actually get better mileage. A vacumn guage is really the way to tell how hard and how effecient it is running.

People have been claming 15-20 HP with a tune.


See my post in THIS THREAD for calcualors for finding out RPMs with different gears and tires. The linked excel spreadsheet is best, tells you speed at RPMs in each gear.

E.g.

I did the overdrive ratio of a 4l60E .696 OD ratio

* Differential Gear = 4.10 to 1
* Transmission Gear = 0.70 to 1
* Tire Diameter (Inches) = 31.00
* Engine RPM = 2000

Computation Results:
# Computed Vehicle MPH is 64.27
 

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Discussion Starter #10
i have the 4.3l, i know, not the ideal pulling motor. but i know there is alot of potential in it though.i just have to figure it out and get the right stuff on it. i think i'm going to ditch the cam idea since it will void the warranty and affect drivability.instead of the cam i think some 3.73's or 4.10's as mentioned above is the way to go or maybe 3.90's if they definately make them for our trucks.i need to squeeze all the power i can get from it since i'm pulling 6500+ lbs. so Gears,K&N Intake,and Nelson Tune is the way to goi guess.any other suggestions on this setup or will this combo be ok?

thanks,
Cody
03 Sierra
87 T(400hp sleeper)
 

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turbocody said:
right now i have 3.42's, but i want to keep my gas mileage up.but when i'm on the highway doing 65,it struggles in OD and kicks down to 3rd and pulls.i want alot more low down grunt power and gears would help but this truck is driven every day. i'm probably going to go with some 3.73's down the road, but my question is would all the mods listed above help me out? i mean, the cam alone is probably worth a solid 15hp-15-20Tq right?

thanks,
Cody
03 Sierra
87 T(400hp sleeper)

i have 4.10s and after some tuning i get 19 mpg highway...
 

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Yah a 4.3l and 3.42, you definatly would want 4.10, I have a reg cab with 3.42 and a 4.8 and i can't stand the gearing. Thats why my truck is scheduled for 4.10 at my local 4wp store on the 26th of this month :D. I'll let u know how the gears are if u havn't done anything yet. I just got my tune in and i love it so i'd say get that too...as for an intake, save yourself some money and get a k&N filter and a new intake tube, gains will be about the same that way...i also de-screened my mass airflow sensor
 

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I'd forsure go 3.90 or 4.10. That really shouldn't kill driveabilty and mileage. Read that previous thread.. had some good info in it including link to 3.90 manufacturer.

Use that calculator to see what will work for your situation, remember lower RPMS don;t necessarily mean better gas mileage, you might be better off towing in 3rd rather than OD (vacumn guage can clarify).
 

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patio furniture breaker
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i have a question about the 4.10 gears. i have a 2003 V6 5 speed(NV3500). last night, i meet up with 5.3 Vortec in Harrison. going up the hills through the mountain i had to downshift to get up the hills, or leave it in OD and boog up the hill. i paln to lower this truck 3/6 and get some 20's with probably 275/45/20 tires. would the 4.10 gears make that much of a difference? would they help with in town driving? do the lower gears help with towing? the gears should make it quicker of the line, right? how much have you guys paid to have it done, or is it something the could be done in the driveway? would the dealer be able to change them? (my wife works there)
 

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Here are some options, that do not require going into the engine (cam) or taking apart your axles.

1. Custom 91-93 dual-octane tune. A 93oct tune can add up to 30HP and 25TQ at the flywheel on a stock 5.3L (not sure about the 4.8, but I am sure it is comprable). Also, if you are towing with 93oct gas and the motor starts to detonate it will pull timing by going to 91oct tables--this is good. Will also increase MPG's.

2. Get an LT1 or LS1 electric fan and have someone like nelsonperformance program your PCM to control the fans, they also supply the wiring harness for this setup--a real plug and play. This is said to free up about 10-15hp and 15-20tq. Will also increase MPG's.

3. A billet overdrive (3-4) servo. Much more holding power in OD. A must for towing.

4. A CIA (K&N, Volant,etc.)

5. Small diameter equal length long tube headers. Known to add bottom end TQ.

6.Cat-back? Why not. More for HP than TQ though.

Oh crap, I just saw that you have a 4.3L.

1. Supercharge it.

2. Done

=Dave
 

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Id go 4.10s, they wont hurt your gas mileage when cruising the freeway hardly at all...
 

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diamondd2 said:
2. Get an LT1 or LS1 electric fan and have someone like nelsonperformance program your PCM to control the fans, they also supply the wiring harness for this setup--a real plug and play. This is said to free up about 10-15hp and 15-20tq. Will also increase MPG's.

I would not reccomend for towing. There is no way that an electric can pull the same amount of air as the old belt with the engine wound up a little. Some of those long steep grades can humble the toughest truck anyday. On a long hill power is an issue, but heat can be a bigger one. At least if you are cool you can keep going even if only in first gear. Remember, they had to design these trucks for the what if situation. The majority of people woudl be more than sufficient with electric fans, but when towing at capacity, those few people who do that can't get away with it. I really sincerly think that if they were as good more manufacturers would use them. As far as I know not one major brand of fullsize trucks uses electric fans from the factory. There must be a reason other than it has always been that way. Especially with the HP race that has been going on between each brand. With the intended use, towing, I would not reccomend this modification.
 

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jebx said:
I would not reccomend for towing. There is no way that an electric can pull the same amount of air as the old belt with the engine wound up a little. Some of those long steep grades can humble the toughest truck anyday. On a long hill power is an issue, but heat can be a bigger one. At least if you are cool you can keep going even if only in first gear. Remember, they had to design these trucks for the what if situation. The majority of people woudl be more than sufficient with electric fans, but when towing at capacity, those few people who do that can't get away with it. I really sincerly think that if they were as good more manufacturers would use them. As far as I know not one major brand of fullsize trucks uses electric fans from the factory. There must be a reason other than it has always been that way. Especially with the HP race that has been going on between each brand. With the intended use, towing, I would not reccomend this modification.
2005 models have e-fans
:read:
 

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Sounds like a valid reason not to use an electric fan.

What I would like to know is how much CFM does the belt fan pull and how much CFM do the LT1 e-fans pull?

I can't seem to find this info anywhere.

=Dave
 
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