Under drive pulleys

Discussion in 'General Chevy & GM Tech Questions' started by doublej, Mar 23, 2009.

  1. doublej

    doublej New Member

    was thinking of getting the underdrive pulley set...........anyone with experience? what kind of improvement?

    2007 Classic Chevy Z-71 LT 4 door
    5.3 L K&N CAI
    Flowmaster Exhaust
    Jet Power Programmer
    Jet TB Spacer
  2. TRPLXL2

    TRPLXL2 Epic Member 5+ Years 1000 Posts

    A guy at work installed an underdrive pulley on his 05' Avalanche, and he said it basically picks up the power lag from the AC compressor when it is engaged. I don't know if this is true or not, but I have heard this on more than one occasion. Hope this helps, if not then just ignore me! :lol:
  3. lvz2ryd

    lvz2ryd Rockstar

    Iam interested to know as well what they do for power on a 5.3:jap:
  4. doublej

    doublej New Member

    appreciate your help.......probably won't get..........thanks again.
  5. ahm1127

    ahm1127 Rockstar 100 Posts

    I installed on my 97 Yukon & removed after I purchased new battery. I was constantly having a dead battery & needing jump. 1st jump was needed about 3-4 weeks after install. I didnt notice any difference except low voltage from alternator when stopped.
  6. TrailLeadr

    TrailLeadr Epic Member 5+ Years 1000 Posts

    I guess that's one downfall to them. You might recover a little bit of hp, but the cost is that you either need to install a higher output alt to make up the difference or just suffer through with an alt that spins slower than stock, and as such charges lower.
  7. kcb37

    kcb37 Member

    For the power you get out of them it's nowhere near worth the money. The only time I would ever buy them is for something like a drag car where you are looking to gain even a tenth of a second. But for anything on the street no.
    Also like someone said, the alt will turn slower so it won't charge as much or at all at idle. Causes more problems then it's worth.
  8. silverado05

    silverado05 New Member

    On cars ( primarily mustangs, cobras, Z28's, WS6's and goats ) I have seen thm pick up around 4-5 hp to the ground ( standard trasmission ) never knew they had pullies for trucks.

    typical kits have a alt, water pump and crank pully.

    alt pully is really small, may hurt charging system
    waterpump pully is really big, this will cause you to run hotter
    crank pully is smaller and doesnt really affect much that I know of.

    Are these piggy back type pullies or are you replacing your harmonic damper with the same weight smaller pully?
  9. 04SilverChevy

    04SilverChevy Rockstar 100 Posts

    Instead of going underdriven...just getting the stock size in a lighter wieght would help ya out. I did this to my Cav. Oh course with a car only making 120hp anything will help it lol
  10. j5689

    j5689 New Member

    It's too bad this company called NST doesn't make them for GMs yet, I've heard nothing but good things about their pulley kits from the forums that talked about them

    This guy said his alt actually charged better with the new pulleys:

    Here's some other talk of it:


    And of course the link to the company itself:


    Sorry to necropost btw, although thankfully it was within the last two weeks of posting, lol

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