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95 Suburban 4WD not engaging

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by 95burban, Dec 17, 2008.

  1. 95burban

    95burban New Member

    I have a 95 subueban and the 4wd sound's like it is engaging but nothing no 4wd only 2wd
    it's not the push button kinde I put it in neutral and shift it in to 4wd on the floor board
    any body know why its not working or have the same problem????
    Thanks Gary,,
  2. ct9a

    ct9a Epic Member 5+ Years 1000 Posts

    I have the same type in my '94. You're actually supposed to roll forward slowly while shifting into the 4wd. Even then, it takes a couple of minutes for my light to come on saying it's in 4wd, and even THEN it takes about 25' or so for it to actually engage.

    Oh yeah, welcome to the site!
  3. 95burban

    95burban New Member

    Really i'll try that tomorrow and see if that works thanks..
  4. 95burban

    95burban New Member

    Did't work anyone els have the same problem??:eek:ut:
  5. stimpee

    stimpee New Member

    Here is my understanding of this (I have a 1993 GMC Suburban 3/4ton).

    The engagement of 4wd is a "2 step" process. The first step involves you, which is when you shift the lever on the floor. This engages the transfer case and gets the front driveshaft into the game. The second step involves an "automatic" process in the front differential. There is a "thermal actuator" which engages the diff or the axles (kind of like auto-locking hubs) to get the front axles and wheels into the game.

    I don't know how any Engineer and design group could POSSIBLY design a system which, in most common cases will be used in COLD weather, that requires HEAT in a working fluid to effect the engagement of the 4WD system. I found this out recently, and it almost makes me think that GM deserves to collapse, but I digress.

    In any case, in the older vehicles, this thermal actuator gets "tired" and becomes less reliable, particularly in cold conditions. The simple approach is to replace the actuator. You can find the part online for around $80-$90, and it looks like the swap process is about a 15 minute ordeal if everything goes well. There is also another option wherein GM determined that the thermal actuator was a bad idea (tm) and designed a motorized actuator to replace it. The problem with this is that the hardware is a direct swap, but it involves a bit of electrical work to tap the thing in. I think the parts are around $200-$250 for this swap, and figure probably a 1/2 day or more to get things figured out to install if you are reasonably competent and have some electrical diagrams.

    On my 1993 burb, I have found that quite often going back and forth a bit between D and R will get it to engage (moving a bit forward and back in each case). However if you are already stuck, this probably wont work, as determined by my wife while pulling the horse trailer a few weeks ago. The other thing I have found is that if I engage 4WD, go back and forth between D and R a few times, and then shut the truck off for a few minutes, that when I restart the truck it will engage.

    You can give that a shot for a short term fix, but I would probably recommend changing out the actuator.

    You can find a bit more info on the following link:

    http://www.automotiveforums.com/t173603.html

    Good luck!

    Steve
  6. 95burban

    95burban New Member

    Ok so my front drive shaft is moving but no 4wd im going to get the 4wd actuator today and see if that is it,,
  7. 95burban

    95burban New Member

    Actuator was bad I replace't it and now it works thank you guys,,
    It was $105. bucks at NAPA ..

    PS.
    Oh yeah make sure you guys check your transfer case.
    I just add'd 2 quarts of dexron three it was almost empty good thing I check it (WOW)
  8. ct9a

    ct9a Epic Member 5+ Years 1000 Posts

    Glad you got it working!
  9. Trophy

    Trophy New Member

    94 Suburban 4Wd Not Engaging

    Thank's for the tips -I will try them. We are in the middle of a pretty good winter storm and it is cold , and lots of snow banks to play in.

    Gary or Trophy
  10. unplugged

    unplugged Epic Member 5+ Years 1000 Posts

    As every seasoned 4wheeler will tell you.....engage the 4wd early and often. Don't wait for the going to get tough. Usually I engage 4wheel as soon as the tires leave the pavement.

    The thermal actuator can get you in trouble when you plunge into a mud bog, river or a snow bank. Right when you need 4wd, it disengages. Posi-Lok makes a cable operated actuator that is another way for manual control of 4wd engagement.

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