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  1. #1
    Master Mechanic
    KyleZ71's Avatar
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    Jun 2010
    York and Wilkes Barre, PA

    Default Underdrive Pulleys

    I've read that aftermarket underdrive pulleys can lead to an increase in fuel mileage and and increase in horsepower as well. I've been told that these are not that good of an investment, so has any one here installed them or what are some thoughts on them.

  2. #2


    I've heard good and bad, depending on your driving style and how your truck is equipped. If you do alot of high RPM driving the smaller water pump pulley saves gas. If you have a massive amp & other additional power draws the smaller alternator pulley causes problems.
    Still Loyal to GM after all these years...:shocked:
    2006 Impala LT 3.5L
    2005 Silverado WT small cab/longbed 4x4 4.3L V6
    1999 Grand Am 3.4L in TX w/ our youngest
    1993 GMC Jimmy 4.3L 4 door 4x4 'Ole Rusty' - 'SOLD'
    1988 S-10 small cab/longbed HT3.4L Crate Engine
    1970 Nova 250 I-6, factory 3 sp floor shifter.
    1968 Chevelle 'Nomad' Wagon 250 I-6 w/ 3 on da' tree.

  3. #3


    I've read that they can help release up to 12HP but don't know anyone personally, who has installed them. Seems like a quick, cheap add-on for that type of HP gain, if they do work. Best way to determine if they work is to buy the pulley and have your truck dynoed before and after installation. The old "butt-in-seat Dyno" can just be the placebo effect. Listen to wis bang and use the least amount of additional power draws.
    2003 Silverado 2500HD 6.0L Vortec V8
    2" Body Lift
    3" Suspension Lift
    Skyjacker Hydro 7000 Shocks
    Skyjacker Steering Stabilizer
    35" Tires with 20" American Racing Rims
    Velocity Cold Air Intake
    Billet Throttle Body Spacer
    BBK Performance Headers
    MBRP Cat-Back Exhaust System
    DiabloSport Predator- Soon to be tuned by Diablew

    "Soon to be leveling-kit"

  4. #4


    I had a set on a my IROC Camero years ago and I hated them. The slowed the power steering down and made it hard to steer. Also my alternater didn't charge like it should. I ended up removing them. I think there fine if all you do is drag race.

  5. #5
    Master Mechanic
    KyleZ71's Avatar
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    Jun 2010
    York and Wilkes Barre, PA


    Thanks just wanted to know some peoples thoughts on them.

  6. #6


    I've used them before, while I did get a horsepower increase at the rear wheels the side effects like poor power steering response, terrible recovery rate on my battery charge, weak A/C, and prematurely toasted 2 alternators I didnt think the HP increase was worth the hassle. As was posted if all you do is race the vehicle this is a great performance enhancing mod, for a daily driver it might be worth a second thought.

  7. #7
    Master Mechanic
    KyleZ71's Avatar
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    Jun 2010
    York and Wilkes Barre, PA


    Did not know that at all. Thanks guys, I'd rather keep my silverado without the ten extra horses and without the extra hassle.

  8. #8


    i was just reading up on this, and this thread definitely just helped me make up my mind, no underdrive pulleys for me!
    2000 Chevrolet Silverado

    4.3L V6, 4L60E, 2WD, Single Cab
    Airaid CAI
    Poweraid TB Spacer
    Flowmaster 10-series exhaust (dumped)
    Edge CS insight monitor
    4.10 gears
    Limited-slip differential
    LS-1 Dual Electric fans
    Corvette tranny servo swap

    Head Unit: Alpine
    Speakers: Alpine SPR-60C 6.5" component set, 4X6 Infinity Kappas
    Subs: 2-12" Kicker CVT's
    Amps: Alpine-M1000 (subs), Alpine MRX-F65 (Speakers)

    305/70R16 NITTO Terra Grapplers
    16" PROCOMP 7089's
    2" leveling kit
    3" Fabtech Spindle Lift Kit
    Front/Rear-Bilstein 5100 shocks

    35W HID Low Beams
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    RIGID dually D2, flush mount, wide beam
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    Russell braided steel brake lines
    Powerstop-red powdercoated brake calipers
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  9. #9
    Master Mechanic
    KyleZ71's Avatar
    Join Date
    Jun 2010
    York and Wilkes Barre, PA


    yeah i did the same thing. a lot of hype, but you dont hear of the negatives
    Objects in mirror are losing

    2003 Chevy Silverado Z71, 5.3L, K&N 57 series, 2.5'' Flowmaster Super 10 series dual exhaust , Corvette Servo, McNew Automotive Dyno tune, SS gauge cluster, Extang Trifecta Tonneau, Pacesetter shorty headers, Goodmark cowl hood, Sony Xplod speakers, Kenwood DDX-470 exhaust tips, 16" Ultra Badlands polished wheels, Pirelli Scorpion ATR .

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