why is the blazer not shifting into 4-wheel drive?


Asked by anderson970 Nov 28, 2006 at 05:08 AM about the 1994 Chevrolet S-10 Blazer 4 Dr STD 4WD SUV

Question type: Maintenance & Repair

When the button on the Blazer is switched from, 2-wheel drive to      4-wheel, the transfer case is not shifting. why?  Do u thiunk it is the switch, in the Transfer Case its self, or something else could be causing it?

15 Answers


It could be any of these. I found a forum for you that walks somebody through diagnosing it. Hopefully this will help! http://www.carjunky.com/messageboard/data/1099.html

72 out of 72 people think this is helpful.

old body s-10 almost allwaya a bad switch or pluged vacc.line

17 out of 17 people think this is helpful.
Bobby Krueger

It depends... are you letting off the gas when you shift into 4-wheel? Because thats the problem I've always had... I forget to let off the gas.

2 out of 2 people think this is helpful.
Ed Rose

There is a vacuum line that runs from underneath the blazer that likes to come undone. It has happened to me, if that is the problem you just need to trace it back to under the hood and rehook the vacuum line

14 out of 14 people think this is helpful.
Not Active

sounds like a bad acuwater,locaded under battery tray,is a round plunger like deal has a rubber diaphram.replace this your 4x4 should work 40 bucks at chevy dealer.

8 out of 8 people think this is helpful.
Cody Doud

this propblem can be caused by 1 the encoder motor/transfercase motor 2 the transfercase switch 3 vaccum actuator under battery tray 4 broken cable from actuator to front diff. now we know the possible problems lets check them individualy fist the encoder motor when your in nutral and press the 4hi button does it flash and just never go in? can you hear an electric motor? after you press 4hi get undernieth the blazer and check if you can turn the front drive shaft by hand? in not this is a good thing and means your transfercase is locked in four wheel drive. if you can turn the drive shaft by hand i would replace the encodermotor (any where from 130$-150$ at a parts store and you do the work your self second is testing the vaccum lines after your transfer case is locked there is one line going from the back of the plenium to the switch on top of the transfercase when the engine is running it should have vaccum when you put it in 4hi it switches the switch and provides vaccum to the front actuator under the batery tray (this is the hose i think one of the privious posters talked about) make sure there is vaccum to the hose when in four wheel drive and if there is no vaccum i would replace the vaccum switch (10$-20$ at parts store and you do the work your self) if there is vaccum then you need to test the actuator it self you should be able to see it move when 4wheel drive is turnd on and off if it dont move the diphram could be tore and if it does move then very very very unliky your cable from the actuator to the front differntial is broken and i dont know what would be wrong hope this helps let us know when/if you fix it *the picture is of the actuator under the tray

36 out of 36 people think this is helpful.
Andrew Trufant

rock it back and forth in drive and reverse and the light should go out.

1 out of 1 people think this is helpful.
Josh Betz

under the baterry ( you also have to remove the battery box) there is a vaccum pod which shifts the transfer case from 2 wheel to 4 wheel check to see if its bad

6 out of 6 people think this is helpful.

I just fixed this problem on my 2000 blazer. It was the 4 wheel drive solinoid Napa part # 600-2296. I didn't buy it at Napa. I found one in the Salvage yard for $15.00. My was located in the middle of the firewall. It actuates the actuator under the battery. I found this problem by reading the posts on this site. Saved me a lot of money and I appreciate it. THANKS

10 out of 10 people think this is helpful.
Steven Howard

In some cases UT would be the vacuum actuator located on top of the transfer case, it could be a 3 prong or a 2 prong that has vaccine lines going to it, it gets clogged and won't engage

4 out of 4 people think this is helpful.
Joe Heron

i hve 2000 blazer it wont shift into 4wdrive when hit button it say awdrive i just dnt get it and light says serice 4 wheel

5 out of 5 people think this is helpful.

On my 96 blazer it was getting no vacuum to the actuator ( some but not enough to pull the cable) so I replaced the actuator and cable. Still nothing. I replaced all the vacuum lines and the vacuum switch. Still not enough. I knew it was had to be something in the transfer case vacuum switch because I hooked a vacuum line directly to my actuator and it worked. so it was getting vacuum to the switch just not exiting. I took the switch off leaving the lines on the switch pushed the ball in to activate the switch. I noticed that the actuator was still collapsing some but not enough. On top of the vacuum switch is a rubber adaptor that the lines connect to. I took that off and hook the lines direct. and it fixed the problem. obviously the adaptor was not getting a tight enough seal on the switch to contain the vacuum. hope this helps

1 out of 1 people think this is helpful.

do this remove the battery and tray. inspect the actuator under the battery. make sure the cable moves freely. hook the battery up start the blazer. unhook the battery, take it out. see if the actuator has collapsed and pulled the cable. the actuator should collapse all the way if proper vacuum


my 4 wheel drive will not do anything. it use to flash in hi but not go into 4 wheel drive. it would go into lo, but not high range. now when I push the buttons it will not even attempt to change. no flashing lights, no nothing. what could this be?

1 out of 1 people think this is helpful.

it sounds like your transfer case shift motor is seized I had the same problem and just replaced mine and now it goes in and out without any problem

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