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Any experience with bypassing vacuum switches to ADD

Discussion in 'Technical Chat' started by Airun, Sep 29, 2010.

  1. Sep 29, 2010 at 6:47 PM
    #1
    Airun

    Airun [OP] Well-Known Member

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    Ok so my T100 left me in a mud hole on a firewood cutting outing with 4wd not engaging. After a little research I decided to try and figure out a way to run constant vacuum to front diff actuator to see if 4wd would engage at transfer case and indicate so with dash light. Viola! Successful after 3 or 4 different attempts and seems to work normally and drives fine in 2wd. Has anyone done this and experienced any long term deleterious efffect? This is primarily a log hauler that sees sub 10 mile trips. I realize the primary drawbacks will be a theoretical increase in wear of front end drive components and decreased economy. Any other problems y'all?
     
  2. Sep 30, 2010 at 3:57 PM
    #2
    DDD

    DDD Shine bright like a hymen

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    I don't understand what you are trying to do.

    Are you having trouble getting the 4wd to engage?

    Are you trying the get the transfer case to go into low range, without being in 4wd?
     
  3. Sep 30, 2010 at 4:01 PM
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    BrokenTusk

    BrokenTusk I support a velociraptor free workplace.

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    I think he said his 4x4 caught fire in a mud hole..
     
  4. Sep 30, 2010 at 7:30 PM
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    Airun

    Airun [OP] Well-Known Member

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    No fires. My 4wd wouldn't engage so I bypassed the vacuum switching valves and ran engine vacuum straight to the actuator line that engages the front diff. Basically the front diff is turning with wheels even in 2wd but not powered until the transfer case is shifted into 4wd. Similar I guess to driving with manual hubs locked when not in 4wd.
     
  5. Oct 1, 2010 at 4:50 AM
    #5
    DDD

    DDD Shine bright like a hymen

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    I have not heard of anyone doing that on a Tacoma.

    I have never had any trouble with the 4wd engaging. I have had some trouble engaging and disengaging the rear diff locker.

    Usually if I drive forward and turn a little the 4wd engages right away.
     
  6. Oct 7, 2010 at 9:29 PM
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    joes06tacoma

    joes06tacoma Well-Known Member

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    I guess maybe the vacuum actuator would wear out faster due to constant vacuum on the diaphram. I have never heard of one going out, so wearing out faster might mean 200K instead of 300k. Other than that, I don't see any issues. No different than having manual hubs and driving around with them locked all the time. I say go for it.
     
  7. Oct 8, 2010 at 7:30 AM
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    Airun

    Airun [OP] Well-Known Member

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    thanks for the input Joes. I hadn't considered the actuator as being a potential weak spot. If it goes it looks relatively easy to open up and manually slide the locking sleeve over and hose clamp the shaft. That would be the next option. Truck has 255k on it.
     
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