GM Truck Club
THE PREMIER CHEVY TRUCK & SUV FORUM
Founded in 2004 ~ We're the #1 Chevy Truck & SUV Forum.
Silverado & Sierra | Tahoe & Yukon | Suburban & Yukon XL | SUV & CROSSOVER
Results 1 to 10 of 21

Hybrid View

  1. #1

    Default under drive pulleys

    so i buoght the asp ud pulley kit that comes with the crank pulley and alt. pulley. after doing so the voltt gauge indicated that it was only pushing about 10 volts whens its supposed to be pushing 14 volts... i was told get a bigger alt. which i did, i went from a 105amp to a 145amp alt. but am still having the same problem. basically im looking for the solution, preff. someone thats run into this problem.... not sure if it matters but its on a 2006 vortec maxx 6.0 motor

  2. #2
    Legend
    stephan's Avatar
    Join Date
    Sep 2010
    Location
    Far West, Oregon USA,
    Posts
    8,610
    Blog Entries
    1

    Default

    Don't know who told you that upping the amperege on your alternator would raise your voltage reading to 14 V at idle but......??
    The higher amp alternator will do better at recharging your battery if you are useing a lot of consumers at the same time, but I don't think it will ever show 14Volts at idle with an underdrive set. Mine never has. I put the March three pulley set (crank, wp, alt) on mine but it was so long ago I don't remember what the underdrive percentage is. It keeps my 6 year old battery charged with the 105 amp alternator if I don't let it sit for more than a week. My voltmeter has read as low as 8 volts at idle lol

    Do you know what underdrive % is?
    At what RPM does your voltmeter come back up to 14V?
    1988 Chevy C-3500 2wd (no pic)
    350 c.i. 5.7 L Stock Block, 4 Bolt Mains
    L-31 Vortec Heads, Edelbrock Cam & Intake,
    Holley 650, Flowtech Headers, Magnaflow exh.
    Jet Trans 700R4, B&M Ratchet, 4:10 gears,
    3" susp. lift kit "shadetree"
    No rev limiter, No speed limiter lol


  3. #3

    Default

    its a 25% kit... but im not sure as to the exact rpms but durring the day when i get up to about 20mph and that brings it to 14v... night time at 20mph its only reading about 12v, im guessing thats due to the small system and 8k hids...

  4. #4

    Default

    I have never heard anything good about under driving the Alt.
    Pavement sucks... :grrrrrr:



    1994 K1500 4x4 Ext. Cab
    PCM chip and Xenon 8000k bulbs
    350cu.in bored over .050"
    balanced Crank, 10:1 compression
    Flat top pistons,cam,ported heads
    Option Racing Cold Air Intake
    Holley Throttle Body Spacer
    Accell Igition, 45kv coil
    FloTech Headers, no CATs, dual exhuast
    Goodyear Silent Armor A/T 305/70-16
    Pioneer SupertunerIII CD USB Bluetooth
    Kicker ZX200.2 ZX Amp
    Kicker Audio COMP 10" Subwoofer

  5. #5
    Legend
    stephan's Avatar
    Join Date
    Sep 2010
    Location
    Far West, Oregon USA,
    Posts
    8,610
    Blog Entries
    1

    Default

    Quote Originally Posted by ejohnson03 View Post
    I have never heard anything good about under driving the Alt.
    more power, better mileage, aluminum pulleys for less rotating weight. 25 to 35% isn't much loss for the alternator.

  6. #6

    Default

    Quote Originally Posted by stephan View Post
    more power, better mileage, aluminum pulleys for less rotating weight. 25 to 35% isn't much loss for the alternator.
    Under driving can give an increase in performance, but I don't think leaving the Alt. pulley will compromise the overall benefits.

    If you are running any additional lights or a large audio system, 25% loss at the alternator will not be a pleasant expierience.

Similar Threads

  1. Underdrive Pulleys
    By Jarrett in forum GM Powertrain
    Replies: 5
    Last: 02-21-2010, 07:40 AM
  2. Underdrive Pulleys
    By Silverado Junkie in forum General Chevy & GM Tech Questions
    Replies: 0
    Last: 02-16-2010, 10:54 AM
  3. Under drive pulleys
    By doublej in forum General Chevy & GM Tech Questions
    Replies: 11
    Last: 07-16-2009, 12:33 PM
  4. underdrive pulleys
    By blacksilverado07 in forum Performance & Fuel
    Replies: 3
    Last: 11-28-2008, 09:39 PM
  5. Performance Pulleys !!
    By wailalghanim in forum Chevy Silverado Forum (GMC Sierra)
    Replies: 3
    Last: 06-30-2008, 01:48 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •