90.... 4x4 not working!

[S10Boy112]

Hi i have a 1990 Chevy S10 Blazer 4x4 4.3L V6...4x4 decided to stop working...when i shift into 4 hi or 4 lo it will not engage....can anyone help?

[carquestman]

depends on whether it has vacum engagement or actuator
either way 99% says that is what it is
if it vacum wich i dont think it is then its probably a leak
if it actuator aka insta trac 4X4
thene it probably just the actuator on the front diff

[that1guy]

Depending on if you have an electronic controlled 4x4 or not. There are 3 buttons on the dash for which 4x4 mode you want. In my blazer my 4Hi doesn't work due to the little dinky bulb in the button is blown. That may be something to check into. I'm not too sure about older blazers.

[S10Boy112]

No, Mine is a floor shift....not an electronic push-button

[tripsblazer]

I have a 1991 S-10 Blazer with Floor shifting 4WD and am having the same problem. For some reason or another, I cannot engage the 4WD. I can pull the handle into 4WD, but it does not feel like I am getting the power up into the front Diff. Also, the indicator light that shows me that I am in 4WD is not coming on and I have already checked the bulb. Any Ideas, it is really plaguing me.

[tripsblazer]

Checked the actuator under the battery and it worked OK. I was then told by the guys over at NAPA to try replacing the Transfer Case Vacuum Switch. EUREKA! 4 WD works great!

[komodo2003]

Originally Posted by tripsblazer

Checked the actuator under the battery and it worked OK. I was then told by the guys over at NAPA to try replacing the Transfer Case Vacuum Switch. EUREKA! 4 WD works great!

Where do i locate the transfer case vacuume switch ??

[tripsblazer]

The switch is on top of the transfer case. It is easy to recognize because it has three hoses running to it. The part is very cheap. I think I paid 20 for it. Good Luck.