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  1. #1

    Question 2000 S10 4wd front diff not engaging!

    2000 S10, 4wd ,4.3 motor
    When I push the 4wd button on dash the transfer case engages but the the front diff does not engage. I found the vac actuator under the battery tray was not being activated (no vac to actuator). I traced the vac line to where it goes down behind distributer. Not sure where it goes from there. I manually pulled on the cable to the front diff,(and clamped it with a vise grip),and the 4 wheel drive works fine. I have asked people at several parts stores as to where the vac line to the actuator comes from to no avail. All they offer me is a part number for the actuator that is under the battery tray.
    Can some enlighten me as to where the vac line to the actuator under the battery tray comes from? I'm not sure if I have a vac leak upstream or maybe another actuator not opening.
    Thanks in advance for your help

  2. #2

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    On my sons 1998 there is a vac switch on top of the transfer case on the drivers side on top of the transfer case just above the transfer case encoder (electric) motor it has 3 vac lines bunched together hooked to the switch one line is a breather another is the actual vac for the engine and the last one goes to the acuator when you push dash switch encoder motor turns shaft on transfer case to engauge 4x4 and internally the shaft has a cam lobe built on it that turns up and opens vac switch to allow vac to go to acuator and pull in cable. If your dash switch shows 4x4 lit up and stays lit up then the encoder motor is probably good but the vac switch is bad. Ijust went threw his 4x4 and worked on all this we ended up buying the vac switch at advanced auto for $17.00 in the help section but the bad news was we only got a little vac threw that switch so we went to gm and got a new one for $50.00 put it in and now it works great. Let me know if you need anything else

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