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

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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 t…

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spelunkerd says:

Hi Mark. Once in a while I stumble across a channel that is very similar to
my own. You’ve got a great attitude, with extra effort and respect for the
time of those watching. Good lighting and great camera angles. I’m sub’d,
looking forward to more.

Juan Morales says:

My 4×4 is stuck in 4hi and in 4lo it blinks, it doesn’t change to 2hi, i
heard a few clicks from the 4×4 control module. the vaccum actuador is
engaged from the start of the motor the vaccum line is always sucking

Scott Brock says:

a BIG thanks for this video….gonna try this stuff first before a transfer
case replacement!!!!! I had no idea were to start

Josh Grounds says:

What if I got suction and the cable pulls but still no 4×4? I get the
famous clicking noise and loud banging coming from the transfer case?

kit8089 says:

Going to check this system in my blazer in the morning. My 4WD engages just
slowly. The little valve you mentioned, is that somewhat of a challenge to

Mike Blake says:

Good video,Thanks 

Auszug21 says:

interesting didn’t know you could removing the battery from a running
vehicle and have it stay running.

Piero Gasoline says:

Thanks ! That video helped me to find my 4×4 issue !

Kyle Hobbs says:

I have a 2000 chevy blazer and the lights for the switches on the dash for
the 4×4 aren’t on. I have a blown ATC fuse but if I try putting a new one
in it blows immediately. I haven’t had 4×4 in a year or so and would like
to fix it but not sure where to start so far. =P Any help or tips would be
greatly appreciated =)>

Craig Player says:

Hey Mark. Awesome videos and great detailed explainations! I just wanted to
throw one thing out there though. As these may be some of the most common
reasons as to why the 4×4 may not be working, there is another possibility.
I just bought a 2003 Chevy Blazer and was sad to find out when I got it
home that the 4×4 did not work. The lights on the dash worked as they
should, actually everything worked as it should! My 4×4 problem? Well, it
was the diphragm on the actuator. It had a tear in it! It was on the
bottom, so it wasn’t visible from just taking the battery and tray out and
simply looking at it, though you could feel it underneath. So if all else
fails for some people who have gone through this problem, check your
diaphragm, make sure there are no tears in it. I bought the part for $50
and it took me about 1/2 hour to replace it. Saved at least $400 by not
having to take it to a shop. Good luck everyone!

Todd Frahm says:

One of the best diagnostic videos I’ve seen. And, unfortunately, I’ve had
to watch a lot of them. Subscribed, and keep up the good work.

Benny Ish says:

NIce vid, grabbed an 2000 jimmy gmc, got the 4×4 to engage. but she wont go
into 3rd sticking in 1st and 2nd manual gears. also seems only the front
tires are spinning no 4×4 lights. so yeahh shes a project. also cant seem
to get it out of sed ghost 4×4.

AttitudeOverTalent says:

Hey Mark, my actuator looks a bit more wrinkly but def has vacuum going to
it and squeezes decent, but my 4wd is still not working. Everything seems
to engage ok. My button takes a few minutes to light up on 4hi, but will
eventually light up. Not sure what the problem is now any input would be
awesome, I understand if your busy though. Great Video. 

silverado819 says:

Maybe you can give a some in site with my question. I bought my son a 1999
Chevy Blazer LT 4×4 I thought I looked at everything on the vehicle before
I bought it for him. But to my surprise the actuator that seats under the
battery has a vacuum line along with the cable… long story short there is
no vacuum line that should be connected to the actuator. I have looked on
many different forms etc even looked on a service manual like Chiltons &
Haynes and neither book shows any type of diagram for the vacuum lines. I
need to know where does that Vacuum line from the actuator go to. Please

honeybear3031 says:

Hey mark I got a 96 blazer and still can’t get my 4×4 to work I installed
the a new cable from the actuator to the front diff and new t-case vacuum
swith still won’t lock in my front wheels I can feel the t-case lock in but
no 4×4 please help…. 

Dan Fleenor says:

Great video got a question thou my 88 s10 will not go into 4Lo the shifter
has a button on it but will not move freely and it doesn’t want to stay in
4hi I going to look at the this part from the video but if that work what
should I do next I Have already been under it and seen the linkage move but
I really don’t where to look next so advice would greatly be appreciated

Bailey Williams says:

mine will go into four low but wont go into high. when i hit hi it blinks
and goes back to 2wd. do you have an idea what that could be?

Brian W says:

On my 2002 blazer, I was able to remove the drivers headlight and look
through a hole beneath the battery tray to see if the vac module was
functioning with engine running and battery in. Headlight removes with no
tools, just two L brackets to pull up.

Justin Youngk says:

Im looking into purchasing a 96 blazer with 180k and the guy thats sellin
it told me it isnt goin into 4 low. He said the issue has started recently.
He’s asking for 2200 for it. By any chance could you give me some more info
on this? 

Shawn Herman says:

HELP PLEASE! 1996 S-10 my actuator always has vacuum…When i engage the
4×4 it does nothing! and 4×4 does not work…Any Ideas???

alan nelson says:

i have 1999 blazer it will go into 4hi but will not go back to 2hi i have
to take the encoder motor off and shift transfer case by hand

Tom Andrews says:

I have a 1996 gmc jimmy sle, i click 4 high or low both lock in the
transfercase makes the sound the front frive shaft moves i cant get mydiff
to lock im almost positive its the cable but i doubt it, is there anything
else it could be, because i don’t wana waste more money trying to fix it,
could it be my front diff shot?

Charles Reynolds says:

My 4×4 worked on blazer until I was fixing radio and unplug 4×4 button then
plug back in and now don’t engage, help please!!!

ironman050284 says:

Hi Mark. I have a 2003 Checy Tralblazer. I just picked it up a couple weeks
ago and found that y 4×4 isnt working. When I turn the knob to awd, 4hi or
4lo, I hear 2 motors under the vehicle engaging, and the light on the knob
goes solid. However, my front wheel dont seem to be engaging. Does the
system in this video apply to my vehicle as well? Or do I have a different
type of actuator I should look at?

Thank you

Colton Rumley says:

Me and my friend are working on his 1998 Chevy S-10 He hit a fence with it
and did some damage to the front end mainly just tore out the headlights
and cut into the fenders a little but its perfectly driveable, But after
this incident when he tries to switch into 4 hi or 4 lo it sounds like its
engaging underneath and the light blinks in 4 hi or 4 lo for a couple
seconds then just switches back into 2wd.

Kara Poling says:

Why would 4low work but only sometimes 4hi work??

GypsyKing7 says:

Very Helpfull Video, trying tio fix my 4wd on Isuzu, it stopped Engaging
Last Winter, Thanks

JFeezy says:

Thanks Mark!

Cory Torrrs says:

that transfer case valve switch thing, is the ball valve thing on the back
supposed to be pressed down ? i bought a new one and it wasn’t…

MrGstore says:

Also, the Gear Shift Cable shifts into gear immediately upon start – like
the cable and/or the trans linkage is resting between “park & reverse” or
“neutral & drive” and if your foot is not on the brake it takes off like a
striped assed ape if you get my drift. (sorry I’m 63 and this is just a
PS the lnk in my previous message is a free and nice VIN decoder

xtremearcher13 says:

Your video has helped me a lot but I still have the 4 wheel blinking light
issue and no 4 wheel drive. Now when I squeeze the rubber diaphragm I can
hear air coming out near the vacuum actuator solenoid. Is this normal or is
it a leak and it needs to be replaced? Thanks, Chad 

Randy Roupe says:

I have a 2001 Chevy s-10 that when I drive in four wheel drive for about
ten minutes or so I’ll hear a loud banging noise coming from under the
passenger side! I’ve changed the actuator and the noise is still there,
need some help here the weather is pretty bad at this time! 

David Reynolds says:

I’m helping my wife’s cousins work on his 1999 blazer 4wd his is stuck in 4
high, when 2 high button his pressed you can here the systems under the
blazer making the normal sounds but staying in 4high.will not
disengage…any help will be greatly appreciated…

Ricky Fleck says:

my blazer 4wd started out engaging half the time i pushed the button.. now
it wont ingage at all. im not getting vacuum to the diaphram. and i hear a
vacuum leak near the firewall when i press that diaphram by hand. HELP

Tracy Pietrzak says:

hi my 95 blazer 4×4 my be stuck in 4 wheel drive previous owner mickey
moused cable removed the actuator can I some how manually disengage back
to 2 wheel drive thanks

Wesley Burton says:

2005 trailblazer just put levaling kit on it now when put in 4 wheel drive
it makes clicking noise need help

Dee DeCorte says:

Actually, once the snow came unpacked, the problem worked itself out.
Thanks anyway.

Bobby B Bristol says:

I have 89 s10 my front dif leaking on dr.side 4×4 works but when i use,the
stearing is all over the place.drives perfect in 2.could it possibly be
bearing?i have extra just wanted to keep that one also.

Austin ireland says:

My 2001 gmc jimmy stl is stuck in 4 lo… My gf drove it in 4lo while I was
outta state cause she dident know how to get it out of 4lo. It acts like it
wants to switch to 4hi, but the 4 hi just blinks while u hear the motor( or
whatever is making noise) wanting to engage but it stopes and 4lo stays
solid. Idk how to fix this. Can anyone help!!! 

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