How to Diagnose and Repair Chevy Blazer and GMC Jimmy 4WD 4×4 Issues

How to Diagnose and Repair Chevy Blazer and GMC Jimmy 4WD  4×4 Issues

Replacement S10 Blazer 4WD front differential actuator:
Replacement transfer case vacuum switch can be found here:

This video is intended to help diagnose and repair four-wheel-drive issues that are common to Chevy Blazer, S10 Pickup, GMC Jimmy, and other GM 4WD SUVs and trucks. While there are other possible reasons why a 4WD system would not engage such as the transfer case encoder motor and computer, the possible reasons I’ve pointed out in this video are quite common and easiest to diagnose. The 4wd vacuum actuator is one of the easiest ways to determine where the problem is on your vehicle.

Replacement S10 Blazer 4WD front differential actuator:
Replacement transfer case vacuum switch can be found here:

Click here to subscribe and don’t forget to select the notification bell!

Mark Jenkins is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to

Due to factors beyond the control of Mark Jenkins, I cannot guarantee against improper use or unauthorized modifications of this information. Mark Jenkins assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. Use this information at your own risk. Mark Jenkins recommends safe practices when working on vehicles and or with tools seen or implied in this video. Due to factors beyond the control of Mark Jenkins, no information contained in this video shall create any expressed or implied warranty or guarantee of any particular result. Any injury, damage, or loss that may result from improper use of these tools, equipment, or from the information contained in this video is the sole responsibility of the user and not Mark Jenkins.

Categories: Computer System

About Author


  1. Mark Jenkins
    Mark Jenkins 17 May, 2022, 01:25

    Replacement S10 Blazer 4WD front differential actuator:

    Replacement transfer case vacuum switch can be found here:

    Reply this comment
  2. Marty McFly
    Marty McFly 17 May, 2022, 01:25

    thanks man! very informative

    Reply this comment
  3. Felipe Valdez
    Felipe Valdez 17 May, 2022, 01:25

    no entendi ni mergas.

    Reply this comment
  4. frieza
    frieza 17 May, 2022, 01:25

    01 gmc blazer 4.3 5 speed 4×4 .my four wheel drive will only stay disengaged if I unplug the bottom vacuum line on the firewall.

    Reply this comment
  5. David Wright
    David Wright 17 May, 2022, 01:25

    Great shots on video great explaining very easy to understand and follow along

    Reply this comment
  6. David Wright
    David Wright 17 May, 2022, 01:25

    That was awesome video

    Reply this comment
  7. Chad Stricker
    Chad Stricker 17 May, 2022, 01:25

    Very good & helpful video sir. Thank you.

    Reply this comment
  8. Albert Davenport
    Albert Davenport 17 May, 2022, 01:25

    Mark, just reviewed your video on diagnose and repair chevy blazer 4×4 issues, great video. My problem seems to be electrical though. When I start the vehicle, 5 seconds later the ATC fuse blows. I've replaced the push button assemble and replaced the TCCM module since it showed corrosion on the pins. But it still blows the fuse. Any idea of what is going on or where I should search for a bad wire? Thanks in advance

    Reply this comment
  9. Gord Currie
    Gord Currie 17 May, 2022, 01:25

    Very well done and informative video Thankyou Mark Jenkins

    Reply this comment
  10. Jamie L
    Jamie L 17 May, 2022, 01:25

    I appreciate the advice, I’m thinking my actuator is toast but I’m getting ready to pull the battery in my 02 ZR2 and see what shape it’s in and go from there. #UPDATE, actuator was in good condition, the cable that works the actuator was corroded, after soaking with WD-40 I manually worked the actuator back and fourth until it got easier and now working properly.

    Reply this comment
  11. Souad Mourad
    Souad Mourad 17 May, 2022, 01:25

    hey ..i have gmc jimmy 1992 4wd not working not moving can i have your number

    Reply this comment
  12. that92s10
    that92s10 17 May, 2022, 01:25

    I have a 1992 S10 pickup and I replaced my actuator today and now none of the 4×4 lights turn on and when the lever is in 2wd the truck grinds and pops like it’s trying to engage but it never does. I put the lever in 4 hi and it stops making noise but only the rear tires spin. No matter what I select (2 hi, 4hi, or 4 low) only the rear tires spin. I have no clue what to do. Can anyone help?

    Reply this comment
  13. Billy Draper
    Billy Draper 17 May, 2022, 01:25

    hey names billy i have a 2004 4.3 L V6 chevy blazzer 4×4 cant get it to shift and gain speed. i let off the gas and hit it again then it goes into second. could not having egnogh transmission and oil fluids.

    Reply this comment
  14. tayronachan
    tayronachan 17 May, 2022, 01:25

    thx for the "how to"

    Reply this comment
  15. L Floyd
    L Floyd 17 May, 2022, 01:25

    How is the truck running without the battery being connected?

    Reply this comment
  16. efawf
    efawf 17 May, 2022, 01:25

    had problems with my 4×4 before. this time the button switch on my dash is not lit up anymore, cant even engage my 4×4 to see what the issues is. Any help or advice would be greatly appreciated.

    Reply this comment
  17. Charles Boyle
    Charles Boyle 17 May, 2022, 01:25

    98 chevy blazer xl. Starts and dies after start

    Reply this comment
  18. jordan clyde
    jordan clyde 17 May, 2022, 01:25
  19. souad kalamouni
    souad kalamouni 17 May, 2022, 01:25

    hi how i wil shanget? can i chat you WhatsApp?

    Reply this comment
  20. Rob Sale
    Rob Sale 17 May, 2022, 01:25

    I can't find video how you found leak

    Reply this comment
  21. Louis Gallaher
    Louis Gallaher 17 May, 2022, 01:25

    My light lits up but when i drive on 4hi on my 02 blazer the front wheel dont spin when my back wheels spin

    Reply this comment
  22. Jonny Sprague
    Jonny Sprague 17 May, 2022, 01:25

    I still don't fucking understand why they went with vaccum on all that crap….

    Reply this comment
  23. Matt Huey
    Matt Huey 17 May, 2022, 01:25

    See im having trouble with my 99 chevy blazer….press button it lights up…looks good…but seems like its not working?? Hmm glad found your video!👍

    Reply this comment
  24. Deven Gaston
    Deven Gaston 17 May, 2022, 01:25

    Could this part cause a humming at like 50

    Reply this comment
  25. Detroit iron rescue
    Detroit iron rescue 17 May, 2022, 01:25

    This is why I only have 4×4's with NP 205 with Manuel hubs.

    Reply this comment
  26. Eduardo Martinez
    Eduardo Martinez 17 May, 2022, 01:25

    Thank you! my 4×4 was acting up on my plow truck in the middle of a snow storm i manually pulled the wire and sent it. got the job done saved me a lot of money.

    Reply this comment
  27. Stephen D
    Stephen D 17 May, 2022, 01:25

    In two wheel drive is only one wheel supposed to spin? Thats all that spins on mine, and I get stuck a lot.

    Reply this comment
  28. Stephen D
    Stephen D 17 May, 2022, 01:25

    Super helpful…well done thank you!

    Reply this comment
  29. Edward Medina
    Edward Medina 17 May, 2022, 01:25

    Good info thanks

    Reply this comment
  30. dpatt45
    dpatt45 17 May, 2022, 01:25

    Very interesting but, I put my 2001 Jimmy into 4WD it would not move forward or backwards and wouldn’t go back into 2WD. Also makes a grinding noise if I try putting it into park with the motor running. Any help gratefully appreciated, I am at a loss.

    Reply this comment
  31. Lucky Piston
    Lucky Piston 17 May, 2022, 01:25

    How did u not nuke the alternator by disconnecting the battery ?????

    Reply this comment
  32. lary gee
    lary gee 17 May, 2022, 01:25

    What if the 4wheel lights at the sifter stay on in and out of 4 wheel? Any idea?? Thanks

    Reply this comment
  33. george milina
    george milina 17 May, 2022, 01:25

    Great. Vido. Very. Helpful

    Reply this comment
  34. American Gigolo
    American Gigolo 17 May, 2022, 01:25

    Its August 18 2020. Just bought a GMC jimmy 2000 FOR $1000 dollars with 185000 miles . This truck is in great condition. Only problem was da 4×4 was not engaging saw you video man this truck its in BITCHING PERFECT conditions thank you saw much… best deal of my life

    Reply this comment
  35. steve bigler
    steve bigler 17 May, 2022, 01:25

    Mark, at 4:20…. when you shut down, you lose vac, and it returns to 2wd (right?)… so is the DEFAULT SPRING PULL at "stay in 2" mode? So if we bypass the vac with a mechanical pull cable (think choke) it needs to be a 'pull and lock' version?


    Reply this comment
  36. Shane Conda
    Shane Conda 17 May, 2022, 01:25

    Hey brother. Just wanted to say thank you. After watching your video and repeating your process on my truck it now works flawlessly

    Reply this comment
  37. Barret Harms
    Barret Harms 17 May, 2022, 01:25

    I never use Greece were graphite and a boot will do

    Reply this comment
  38. Daniel Otero
    Daniel Otero 17 May, 2022, 01:25

    What else could be the problem I get vacuum to the actuator it sucks all the ways in but my front drive shaft spins but the front wheels dont

    Reply this comment
  39. soldier4christ soldier4christ
    soldier4christ soldier4christ 17 May, 2022, 01:25

    I have the 99 gmc jimmy 4×4 with 2hi, 4hi, 4lo, and auto 4wd. When I press any button it just blinks. I have a service 4wd light on dash. Can someone tell me what the correct procedure is for switching to 4wd.

    Reply this comment
  40. Sean Brown
    Sean Brown 17 May, 2022, 01:25

    I hear mine click in but the when i get into sand to off road the rear will grip and spin to try to get out but the front wont do anything.

    Reply this comment
  41. Richard Lee Cabrera Jr.
    Richard Lee Cabrera Jr. 17 May, 2022, 01:25

    Would the location be at the same spot on an 84 k5?

    Reply this comment
  42. Ray Ray
    Ray Ray 17 May, 2022, 01:25

    My 2 high won't go in is stuck on 4 high what do you think might be the problem

    Reply this comment
  43. Jos Cram
    Jos Cram 17 May, 2022, 01:25

    What about a 2001 Izusu Trooper 3.5L LS?

    Reply this comment

Write a Comment