Hi there;

I read what you said about the wires on the Blazer, but mine were not corroded.  I took it off and cleaned it up anyway and it came back on, but as soon as I turned the key off she was gone again.  I don’t have any lights lighting up on the 4×4 switches.  Service 4X4 light is on in the dash.  I don’t know what is going on.  Any suggestions or advise greatly appreciated.



47 comments on “4X4 PROBLEM S10 BLAZER

  1. it sounds like the transfercase is working. but just remember 4HI is a on-demand thing and wont engage unless the rear slips but sometimes it will go ahead and shift. but back to tha question if the light is working and u replace both modual on the transfercase and the push button cluster thin there is a acsuwater under tha battery plate that a cable runs from and gose to tha front diff there could be a pin hole in it so check that i have tha same truck as u so if this works it might save me some trouble. lol

  2. look under the battery, GM had this great idea to put a vaccum diaphram where acid can drip and burn a hole in it. check this and possibly go to a junk yard and find another vaccum switch. Have someone engauge 4×4 while your under truck so you can hear the switch engauging to be able to find it. its right underneath on the tranny. this is a 400 -600 part new. if you have a hole in the vaccum diaphram,, use a bike tire patch kit to fix this..a little 25 cent fiix for you.

  3. I am a girl and I don’t know anything bout cars but I had same problem with lights on dash. Also when I pressed the brake my reverse lights would come on. My husband found out that my tow package wires had been cut and were fused with other wires. They changed some wires and I’ve never had the problem since. Just a thought.

  4. SOunds like the same problem I have with my 2003 s10.
    I cleaned the grounding point at the fuse and relay box under the hood. The grounding point farthest front of box.
    I had alot of intermitting issues including the 4×4.
    After I cleaned it, everything started working again!
    who knew?


  5. Hi this might be too late but I believe the sound you are hearing is due to the actuator not fully engaging, perhaps the cable is corroded and or stretched or the vacuum actuator is leaking but either wy that sounds like what you are having a problem with, you can check it by jacking up the front end putting the truck in neutral and manually moving the actuator cable in and out by hand while having someone rotate the front wheels for you, if you dont fix that soon you will end up with damaged gears if they aren’t already and then instead of a new cable and or actuator replaced you will need to replace most of the front axle components, hope this helped, cheers ^^

  6. Mechanic wasn’t BS’ing you. My brake warning light also came on after the ABS light was on for a while. What a great way for the stealership to get you in for service. Just to note, my Blazer stops on a dime, no brake problems at all. I’m glad the ABS isn’t working anyways. If one wheel slips the ABS kicks in and send you right into the intersection, even though the other wheels have traction.

  7. I can be driving along and push the pedal and it is solid, no brakes. If I pump them several times they usally start working again. Some times I have to jump on them. Then the front end goes all over the place. After that every thing is normal, until it happens again.

  8. Ok ! this is how you reset your 4×4
    Don’t start your truck, just turn the key until the lights in the dash comes on then,
    put your truck in “Neutral” then,

    if your truck was in 4×4 LOW, you got to press

    the 4×4 High first, wait five seconds then press the
    2×4 HIGH.

    If the truck was in 2×4 HIGH then, just press the

    2×4 HIGH.

    That should reset everything.
    It’s working on mine

  9. Hi guys , this front end with the vacum and cable to engage the front axle will not do anything unless the front driveshaft will turn.if the transfer actuator motor is stuck,whitch will happen sometimes,the front driveshaft will not turn and it won’t matter what you do with the cable running to the front diff.so if the front shaft is turning and you pull the cable,this should engage the front wheels,if they dont there is a problem inside the front axle.

  10. I have recently bought an 01 LT Blazer 4×4. Had to do a good bit of maintenence to it to get it running right, but my main issue is now this: When I go to lock it into either 4 HI or 4 LO, I hear the diff lock in, but while in sand which I have found is the best place to test 4 wheel drive, I get no action from the front tires. But in reverse, they lock in just fine. Now another thing is that the lights on the push buttons never stop blinking as if it never actually locks in, but from the sound, I know that it has. ???????

  11. The problem I am having seems to be with the 4 wheel drive. When driving in 2wd, the passenger side front wheel has a loud mechanical whirring noise, related to speed, there is some kind of friction slowing down the vehicle. I checked rotors caliper for rubbing, they’re fine. Second thought was wheel bearing but was skeptical because That wheel bearing has less than 5,000 miles on it. Put the truck on jack stands and put it in 4wd. Front axle not engaging. the 4wd lights in the cab work, can hear relay click, can hear transfer case engage, but axle is not turning. Front wheels do not spin freely in 2wd or 4wd while on jackstands. They are hard to turn by hand. However, even though axle is not turning can still hear the noise when in gear and in 4wd. When I apply the brakes, the noise stops with the wheel. (which isn’t even turning??) The noise is not coming from the rear, there is no noise when the truck is in 2wd, and the truck is on jackstands. The noise is only in 4wd or when the front wheels are in motion in 2wd.

    If anyone has any ideas what to check next I would appreciate it. Going to check vacuum lines now, after reading other posts, but I fear my forks in the front diff may be the problem 🙁

  12. I realise his question was a while ago, but to anybody else who stumbles across this I thought I might add, given his symptoms, check the catalytic converter for flow. A plugged cat can cause loss of power, trouble starting and overall lack of performance. Before you spend all the money on a tune up, etc.

  13. I would be willing to bet that your mass air flow sensor needs cleaning. Had the exact same prob with mine. Its a simple fix. Buy the cleaner at any parts store. They will be able to tell you where the sensor is. Really simple takes about 15 mins.

  14. We have a 97 Blazer and last time the Brake light(parking brake light) came on, I did everything you can imagine to try and make it go away. Then, after noticing that the truck was pulling I removed the rear drums, and found the problem. The auto adjusters for the rear brakes were stuck solid, and the brakes were no working at all in the back, after replacing the whole spring assembly and shoes then re-adjustusting the rear brakes, the ligh went out and the pullin stopped.
    I suspect the smell your mother is gettin is from the excessive load on the front brake pads du to the rear not working anymore, eventually the front pads will wear out completely. I suggest if ya replace the brakes again, do all four wheel, and replace the rear spring kit, then readjust the back brakes. If the rear ones are not adjusted the light will just continue to stay on and wear out the front yet again….Hope this helps.

  15. Okay! My uncle was suppose to get my original transmission rebuilt, but I found out that he had it replaced with a junkyard transmission. Ever since installation I have been having various problems. I tried to engage my 4 wheel drive hi. The light is on but when I push the gas, I hear this very loud banging noise as if the wheel is going to fall off. When I stop accelerating, the noise stops. When I put it in 4 wheel drive lo the light blinks. When I put it back in two wheel drive it works fine. I don’t know if it has anything to do with it but since this has happened, my ABS light also came on. What could be the problem because I was thinking that maybe he put the wrong transmission in and not to mention when I put my car in gear, the light that comes on to show you what gear you are in does not work properly. For example it will not highlight in neutral, drive 2, and delay highlighting in park and drive.

  16. If its on the transfer case it will be on drivers side at the top rear. One is a breather linethat should be zip ties to tranny tube . one to your vacuum can 4 the 4 wheel drive and the last one goes onto the intake. If you take the nipple off the t case make sure it goes back on the same way it came off it can fool ya if you don’t pay attention. I learned that the hard way lol. If anyone has to change a heater core on one have fun

  17. I own a 1999 Chevy S10 ZR2 with a 4×4 problem – it doesn’t work. 4Hi doesn’t seen to do anything and it slips out of 4Lo right away. When I push the 4Hi button, everything seems normal. The light on the panel works fine. I hear the click under the glove box, I hear the transfer case motor shift, but the 4×4 doesn’t engage. I first assumed it was a vacuum issue, so I changed the actuator switch on the transfer case and also the actuator under the battery (when I pulled the actuator, it was filled with oil – any idea how that happened?) I also blew out the line that went from the actuator back to the actuator switch on the transfer case – there was oil in that too. Still doesn’t work.
    So I put the entire truck on stands, getting all four wheels off the ground. I started the truck in 2×4, back wheels spin like the should. I push the 4Hi button and front tires don’t move – even though everything sounded like it switched into 4×4 just fine.
    So with the engine still running and still in 4×4, I get out and look underneath. The front drive shaft is spinning at the idle speed but isn’t turning the wheels. This is leading me to believe that the front differential is shot. Is this so, or am I missing something??
    The blower inside only works on the vent setting. When you switch it to floor or windshield, nothing changes. Could this be linked to the fact that there was oil in the actuator?

  18. I have a 2001 gmc Jimmy, I have just recently tried using my four wheel drive. Used it one night to go mudding, and now that we are getting snow I am having problems. Use to when my truck was in park I could hit my 4 hi button and it would lock in just fine, now if my truck is in park my four wheel drive won’t do anything. If i put my truck in neutral I can get it to lock in 4 low, but I can’t get it to lock in four hi for anything. I have my torsion bars tightened so that I can clear 31×10.50×15 could this have anything to do with my truck not wanting to lock in 4 hi? Please send any suggestions to gmcwebb@hotmail.com

  19. 4×4 worked fine for start of winter season. Always came out of 4wd to 2 wd with very loud thud as if I just hit a 6″ deep pothole. So I tried not to engage 4×4 too often. But 4×4 stopped engaging all together. Delivering the mail in Indiana with no 4×4 has me spinning.

  20. someone told me to check the fuses, but still not working. also have the same proplem as the guy “Kirt” in that my dash heat won’t transfer from face and defrost to heating your feet. also my truck doesn’t warm up much past 150 degrees, so it never really warms up.. any ideas on how to fix this?

  21. love your comment to the import guy. out of a job yet? keep buying foreign. i got my 99 blazer at 160,000 for $2000 been very happy with it , done a muffler,wheel bearing,u-joint, small price to pay for a reliable Chev. found your page when i googled blazer 4×4 light found a lot of good info. just went to the post office and it poped on when i turned the car on i use it maybe once every 2 weeks so it could be a million things gonna take it to my buddys dad hes building a 67 vette from the ground and hes got all them fancy computers so ill see what code pops up. awesome blog man.

  22. I agree with Kyle, I myself own a 95 4×4 blazer and I have owned it for four years now. I may complain now and then about it, but so far it’s the best vehicle I’ve had or owned for that matter. it gets me from point A to point B and everywhere else.. If and when I decide to get another vehicle, it will still be a Chevy blazer. there’s nothing like them,in my opinion. another thing, I am not a kid, I am 61 years young (a kid at heart)! oh and good luck with your son’s decisions about how he drives or repairs HIS blazer.

  23. my 1998 blazer will just go into 4 wh and lo light blinks while driving down road. if i change to 2wh drive it stays untill i stop or shut vehicle off. i was told encoder motor was bad. thanks jim

  24. I agree with Kyle’s reply, and would like to add to it.
    You may also want to think about your son’s driving habits. Anything that can be “made”, can also be broken.
    Another thing to consider, if you are “constantly” needing to take ANY VEHICLE to the mechanic, it may be time to find a new MECHANIC. I have a close and trusted friend, that sells parts to repair shops. He has told me of some of the “dishonest” shops, and the methods they use, to keep their customers coming back for more.
    Another good reason to learn to fix it yourself.


  25. Now when you are talking about the cable under the battery on a chevy blazer that leads from the vacuum actuator to the front axle actuator silenoid (which is the electronic device on the front axle with the two wire plug. Now what the cable does is it controls the drop arm in the front differential, it does not just control the passenger front it controls the entire front axle through the spider gears. Now as far as manually engaging 4×4 you pull and hold tension on the cable you can not do anything back at the Transfer case and control your drop arm!

  26. Hi Kyle,
    I’ve read all your posts dating back to 2007 to current and have learned a lot about how my 4 wheel drive system works. Thank you sooo much for sharing what you know and helping so many people.
    I have a question that I hope that maybe you or one of your readers might give me a clue as to what to try next. My truck is making a a rubbing/growling noise from the passenger side front tire. I checked all the fluid levels, replaced the bearing hub. Still growls. I had a vacuum hose that was unhooked from the box inside the wheel well ( I must have accidentaly pulled it loose when I was changing plugs a couple of months ago)and hooked it back. I checked the vacuum lines, the diaphram under the battery (thought the cable might be sticking and not letting the axle fully release, the cable seemed to go through it’s full range of motion), the brake pads are in great shape, and it goes right into four wheel drive with no hesitation. As a matter of fact when I put it into 4 wheel drive the noise stops completely. As soon as I put it back into 2 wheel drive it starts right back up. I’m fairly mechanically inclined and determined to try to fix it myself to save the money and just so I will know how to do it. I even laid out some bucks last night to buy a 3 volume set of shop manuals for the 2000 S-10 in hopes that maybe I can find an answer on what is causing the noise. Once again thank you and anyone else who would have any input on where I should look next. John

  27. My 1999 Chevy S-10 is making a rubbing/grinding in the front end and it increases with speed. It is not affected by the engine or gear. It softens when I go over and when I turn either way it seems to get a little worse. It would seem that it is affected by the overall downward force on the vehicle. It is coming from the center of vehicle (so it appears). I have had issues with running through brake pads in the past but they appear fine. I have replaced both front hubs as well. Could it be that the front differential needs rebuilding or just bad bearings somewhere in the front assembly. I don’t know if this vehicle is prone to differential problems or if there is a common failure elsewhere?

  28. i have a 2000 4 dr 4×4 blazer and i hear a relay or switch clicking in my passanger floor board. but when i hear it click about 6 to 10 times in a row my service 4×4 light comes on and my actuator tries to engage the 4×4. even when the keys are out of the car. i have filled all the differntals transmission i put a new battery in it i pulled the fuse but it still did it. i need help.

  29. hey i have 1996 blazer my abs brake light wront go off we put all new brakes and calibers and still have half peddle and we get nothen but pur fluid out of it every thaing new still feels like their air in it

  30. I hear this rum rum rum nois when driving so I pulled tire of check hub assembly it’s fine bearings fine put it back together took a ride put I 4 wheel drive not workin it use to work fine jacked it up spun tires forward but hand I could hear the nois sin it backwards no noise is it my transfer case ? When I push button for 4 wheel drive it goes away but comes back

  31. I have a similar problem. i hear a roar from the front passenger tire and when i engage the 4wheel hi it goes away then when i put it back in 2wd the sound comes back. did u ever figure out what it was. cause im stumped. please email me back or post thanx

  32. Hello,
    I need to pinpoint the problem or parts needed to fix. I am a mechanic. I have been out of it for years but actually worked at several shops and worked on many cars. So I do all my own work but need a bit of help sometimes to pinpoint problems. I recently replaced the transmission about 20,000mi ago. I changed the passenger side hub assembly a couple years ago and just changed the drives side hub assembly a few months ago. So, my problem has two symptoms. One, a metal creaking sound when I press the brakes and the weight shifts to the front of the vehicle. It will even sound like a creek pop when I come to a complete stop. I can make it do it if I step on the brakes and let off over and over it will creek pop, creek pop. The other symptom which didn’t happen till I just put new front break pads on, when stopping from high speed at about 30mph or less the drivers wheel wobbles. I let off a bit to releave it some and then below 15mph is stops. When I changed the brakes, the drivers was almost bottomed out and the passenger still had several hundred miles left on them. Possibly from the wobble it ate into the brakes. I just need to know what I should attack on this. And what parts to go pick up and replace on the front end. One other thing it does seem like when I jack up the car the bottom of the wheel seems to point inward and seems to be doing it a few centimeters when it’s just sitting there after driving but It’s so slight I keep thinking I’m seeing things but it could be. Thanks for reading this book! Hopefully you can help me out here. Thanks, Bret 🙂

    • Bret,

      Classic symptoms of bad ball joints. Replace them if they’re OEM, there’s been cases of ball joint separation and the whole thing falls apart while you’re driving!

  33. This weekend headed up to the snow, all was fine the last weelend but this time, my heat and air controls didn’t work and when needed my truck would not lock up in 4X4.
    I have a Manual Shift lever not a button, the Wheel diagram would not light up showing it in 4X4.
    Thanks to all the comments I found that the Vacuum line for the 4X4 and my climate controls all come from a Ball vacumm canister mounted to the hood driver side back at the fire wall. There are several tees attached to the canister, I found the lower one had pulled loose from the Tee, hooked it back up and all was back to normal.
    problem is when the hood is opened the canister is lifted and can pull the same line out, I had trimed the line a week prior when I noticed it was dried and cracked at the end. One inch will do you in.

  34. John,

    I had this exact symptom on my ’97 Blazer. The problem is that the vacuum switch on the transfer case has gone bad. Drivers side top rear of transfer case there’s three vacuum lines in a connector/grommet that connects to a part that screws into the transfer case. You can buy this part at any auto parts store. Transfer case vacuum switch.

    What’s happening is that the vacuum is trying to actuate the 4WD despite you not switching it on, because the vacuum switch is bad. So the growling noise is the fork in the axle trying to engage. Notice how it will stop when you slow gradually and reach about 10mph or so? With a ‘clunk’?

    It’s an easy fix, you can do it without even jacking the truck up if you’re skinny enough! 🙂


  35. The reason your s10 won’t shift into 4wd while your driving down the road is because it’s a clutch gear 4wd transfer and if your driving when you engage it your 4wd clutch is free spinning and doesn’t have time to engage.

  36. My blazer had the same problem. As is everybody else. ets just not buy these. My problem ended up being two things. One someone put the wrong fuel pump in my car. their for it not getting right furl pressure. Also the problem was that the spyder injection system was clogged and not spraying in all 6 cylinder. So had to replace that. maybe something to look into on yours. lol

  37. I have a Chevy Colorado z71 ls I recently installed a four inch torsion lift in the front and 3 inch shackles in the back to fit some 33s being neive I decided it would be funny for a day to crank way down on the torsion bars to where I got around six or so inchs of lift in the front. I drive it around town and all was good. Not taking into consideration the incredibule angle the cv half axles were sitting at I took it on the highway for a short stint. Needless to say I blew out one cv boot and stroke the axle on the adjacent side. I know it’s broke because I pulled the hub assembly here recently to replace some broken lug studs and the cv shaft was by look and feel obviously seperated at a joint. I plan to replace the cv half axle hear soon but my 4×4 still works after a few minutes after engaging my question is is that because the limited slip is engaging to the other side there for getting power to that wheel when the limited slip was engage in the opposite direction and no power was getting to the front wheel due to the busted cv Hal axle. Or is there another problem I should be on the lookout for

  38. Hello every one I’m haveing an issue with my 1991 s10 blazer z code 4.3l v6 2 door 4×4. this issue seems to only happen. During times of the day were the temp and moisture change. During late morning to late evening. the engine dose not have mutch power, eats gass, and very doggy at low rpm. I’ve replaced the cap and rotor, regaped the plugs and checked resistence in the wires and there is no evedance of green and fuzzy also there is no dtc’s. But during the rest of the day the engine runs perfictlly normale. what do yall beleive is wrong?

  39. Sounds like your injector or injectors are plugged and starving the engine. try a can of sea foam in the gas tank.

  40. Hi I have a 99 blazer lt with 4×4 issues there was a broken vaccume line by the drivers side fender, I plugged it and the vehicle engaged in 4 low and Will not disengage I have no lights on the 4×4 selector switch or no service lights on the dash. I made it about half way to work when the truck bogged down, died, then wouldn’t start. And advice would be appreciated thank you.

  41. Here’s a question for you I have a 1998 Chevy blazer4wd when I bought the truck the air conditioning linea and all that pertaining to it were gone.the heat worked fine til a week ago today it started out popping fuses then eventually burning up my deceit wires and catching fire what can I do to fix this my wife and daughter freezein the mornings because there’s no heat…thank you cody

  42. A new Actuator motor will not work “whirr-and-shift” the transfer case. I replaced my actuator motor because after just one shift to 4wHI, it locked in and wouldn’t release. The road was slippery here and I made it home OK with only a couple hard wide turns due to the 4wd. TCCM cicked and the motor wouldn’t whirr-and-disengage. I replaced the actuator motor after manually shifting the transfer case back to Neutral using a crescent wrench (the motor was shipped with the comment it is in 2wd from the factory and make sure the trans/case is, too) The new trasfer case motor has never worked. TCCM is clicking (clean terminals) the dash lights blink “2wd-4wd” a few times and return to “2wd” after a few seconds. My other suspects (vacuum actuator under the battery, vacuum switch on top of the case, firewall vacuum, TCCM, fuel pump fuse, dome light fuse) are each OK by trouble shooting. Anything including “how to troubleshoot the actuator motor” in place or taking it out?

    • Hi Bill;

      Unfortunately, your problem does not sound like something that I have encountered and can offer you no further advise other than what I have already encountered. I am not a mechanic.


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