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4wd doesn't engage

Discussion in 'Chevy Trucks' started by Greenwalt, Jan 6, 2010.

  1. Greenwalt

    Greenwalt Member
    Messages: 75

    94 chevy, k2500. T-case will go into into both 4 hi and 4 low, but the truck stays in 2 hi. I'm thinking it's probably the actuator. Any body else have any ideas? Fairly easy job to replace? Has anyone very tried one of the manual conversion kits?
  2. Greenwalt

    Greenwalt Member
    Messages: 75

    Also, the engagement light does not come on
  3. wakesetter2001

    wakesetter2001 Member
    Messages: 58

    I would guess it is the Peace of Junk hot wax actuator that chevy used stock. It works by heating up wax or grease( somthing like that) to push the locking pin over. Go to NAPA and buy a new actuator takes about 10 minutes to fix and it actuates using a rotory screw that has positive pressure so you can lock it in with out having to be moving.
  4. Greenwalt

    Greenwalt Member
    Messages: 75

    Preference on brand from napa?
  5. Thermos017

    Thermos017 Member
    Messages: 59

    if the light isn't working either then you probably need to change the switch on top of the t-case. there are 2 seperate circuits for the light and actuator on one switch, so if neither are working the switch is probably shot. look at that first as it's a helluva lot cheaper to replace. i think B&B said somewhere they are more common of a failure too. if you go to napa stay away from echlin parts. you'll be replacing an echlin before the plowing season is up.
  6. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    This was for the newer trucks that have the actual motor driven actuators as those are far more reliable than the old thermal actuators like Greenwalts truck would have...and we're all familiar with. :D

    First, if the indicator isn't coming on then the actuator isn't engaging the front diff for one reason or another. Because the indicator switch is on the front diff and is totally independent from anything electrical on the T-case. So if the light isn't on and the fronts aren't spinning then the diff isn't engaged. And of course there can be a few reasons for that. First, a blown 15(or)25 AMP 4WD fuse in the fuse panel. Second, a bad switch on the T-case, broken/corroded wiring down on the diff, or of course a faulty actuator.

    A quick easy test to see if the power and ground is reaching the actuator...

    1) Disconnect the connectors on the diff that connect to the actuator and using a test light check the light blue wire for battery voltage with the ignition on and the T-case in either 4Hi or lo. Should have it.

    2)Check the black wire for good ground. Should be there.

    If both those check out then it's the actuator that's faulty. However if the light blue is dead then either the switch on the T-case is bad, the fuse is blown or that wire is broken/corroded somewhere between the connector plug and the T-case switch. If the black ground wire is dead simply add a new one and ground it on a good grounding source.
  7. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    If B&B's diagnosis indeed reveals a faulty actuator, you have a couple of options.

    IMO, the Posi-Lok is the best way to go. I had one on my 89, and intend to put one on my 97 at some point. One nice feature of the posi-lok is that you can put the T-case in Lo Range, but only have 2wd. This is handy for backing trailers. Or pulling Semi's down the road.

    You can replace the thermal unit with a replacement from Napa or wherever.

    You can put a spacer behind the actuator to get through the winter. A 3/8 drive 13/16 or 7/8 socket works, or you can stuff a lugnut in there. I have done both, they work equally well. I have a socket in my plow truck, a lugnut in her Tahoe. They will likely stay there for at least the winter.

    To put the spacer in is very simply. Simply unscrew the actuator from the axle. Put the spacer in the opening, and reinstall the actuator. You will need to overcome the spring pressure of the CAD, but it is very light. And you may need to rotate your driveshaft slightly to get the CAD engaged. You will feel it line up and the actuator will slide right in. Thread it in fully, and snug it up. Make sure the T-case is in 2hi when doing this so the driveshaft can rotate.

    The instant 4wd is fantastic. I don't know why I drove my truck so long without it.
  8. Greenwalt

    Greenwalt Member
    Messages: 75

    Thanks for the help, when I get off duty tomorrow ill have to check it out.
  9. Thermos017

    Thermos017 Member
    Messages: 59

    so i did it again... my eyes saw one rig and my brain registered another. maybe i should quit posting on here while i'm in the middle of working on a truck. everything seems to be running together in my brain.

    but i stand by my comment on the echlin parts... they are junk. it doesn't matter what rig the part is for. if they don't fail out of the box they will shortly after install.
    Last edited: Jan 7, 2010
  10. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    We're all guilty of that from time to time me included. :nod: