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Under Drive Pulley

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by Goldie, Dec 8, 2013.

  1. Goldie

    Goldie New Member 1000 Posts 100 Posts

    I'm looking to add an under drive water pump pulley to my 07 4.3L engine. Can someone give me a source for purchasing one? I haven't had much luck searching the net for one. I already have the crank and alternator pulleys so I don't need a kit.
  2. clgoch187

    clgoch187 New Member 100 Posts

    Can I ask why you wants smaller water pump or alt pulley? The point of the underdrive crank pulley or to reduce parasitic loss, replacing the other with smaleer pulleys would counter act this andjust make it a bitch to find a proper fitting belt
  3. shaggy08xr

    shaggy08xr New Member

    Where can I get the crank pulley from. I did a light weight crank pulleyon an 08 Toyota Tacoma Xrunner (I know, a Toyota) and really liked the difference in acceleration the pulley gave the truck.
  4. Pikey

    Pikey Moderator Staff Member 1000 Posts 100 Posts

    Many kits include a new belt or tell you what new belt to use.

    Just google GM 4.3L underdrive pulley kit. Summit, Jegs, amazon, ebay.. Everyone has them.
  5. shaggy08xr

    shaggy08xr New Member

    Do the pulleys only come for the 4 3? I have the 5.3.
  6. Pikey

    Pikey Moderator Staff Member 1000 Posts 100 Posts

    The only one that I have found for the 5.3L is Jet Performance, Mfr Part#: 90143. I am not saying that it is the only one. Just the one I found with a quick google search

    - - - Updated - - -

    I guess that this was discussed a few years ago here. People had issues finding them for the 5.3L then.


    http://www.gmtruckclub.com/forum/showthread.php/53575-under-drive-pulleys
  7. clgoch187

    clgoch187 New Member 100 Posts

    For a crank pulley yes. But if you go changing water pump and alternator pulleys your gonna be defeating the crank pulley and ducking up your belt length.
    By going to a smaller pulley on the accessories your actually increasing the Roma of said accessory and adding resistance to the belt that will put more strain on the engine.
  8. Pikey

    Pikey Moderator Staff Member 1000 Posts 100 Posts

    On my 1995 5.0L I did the under drive pulleys. I did the alternator and the crank. It came with a new gates belt number, I went to the parts store with that number and bought the belt. It fit fine.
  9. clgoch187

    clgoch187 New Member 100 Posts

    But what was the benefit of it...you would be back to the stock level of parasitic loss
  10. stchman

    stchman New Member 1000 Posts 100 Posts

    What benefit are you hoping for with an underdriven pulley system? I don't see you getting more than a few horse increase from such a system for a 200HP engine.

    Guys that have superchargers will put a small pulley on the supercharger to make it spin faster increasing boost.

    IMO, an underdriven pulley setup on a stock 4.3L engine is probably a waste of time.

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