4WD on S-10 Blazer

**wideglide55** · 12-19-2009, 10:59 AM

Any Chevy Techs out there that can tell me how to get the 4-wheel drive to engage on my wifes 2001 S-10 Blazer,the transfer case will shift from high to low but won't engage the front wheels?

**D.B.S** · 12-19-2009, 11:03 AM

Have you tried backing up a little? I had one years ago that was the only way to get it to engage.

**punkinhead** · 12-19-2009, 11:10 AM

4wd is vacuum actuated. the actuator is by the battery. This is a very common problem. The rubber boot dries out and cracks. I had this same problem, the shifter engages the transfer case, but the 4x4 doesn't come on until the vacuum engages the 4x4. Hope this helps

**transomstand** · 12-19-2009, 11:19 AM

This is a good overview of how the system works.

http://www.automotiveforums.com/vbul...d.php?t=572914

**oldschoolltv** · 12-19-2009, 11:22 AM

Some things never change, I had an 86 s-10 blazer and had the same problem several times and always when I needed it the most.

**njj502** · 12-19-2009, 11:54 AM

There used to be someone that made a manual lock in for the front end on the 88-99 K series trucks. This got rid of the vaccum assised BS. Should be something for the Blazers too.

Nick

**stvgar** · 12-19-2009, 06:55 PM

Sometimes you can engage it by squeezing the vacuum diaphram to "help" it. It then may work normally until it sits a while again. It's under the battery on that one I think.
Good Luck! Let us know how you make out.

**transomstand** · 12-19-2009, 08:09 PM

Originally Posted by stvgar

It's under the battery on that one I think.

Yes, it's a pain to get to.

Did you just post twice in a single day????????

**Rigaud** · 12-20-2009, 09:35 AM

I have a similar problem on a 99 GMC Suburban with the electronic transfer case and selector pad. It engages when I select 4Hi or 4Low but no front drive to the wheels. When it's in AWD mode I have no problems, it kicks in 4WD as soon as a wheel slips. I'm wondering if mine has the same system and also vaccum accuated. If so where would I look for this actuator? I looked under my battery (left side facing front of truck) and theirs nothing. It's a 5.7L 1500 and I do have the second battery tray without a battery in it on the right side but kind of hard to see anything.

Sorry, not trying to thread jack but figured it was the same subject and near same vehicle.

Cheers

**wideglide55** · 12-20-2009, 01:46 PM

Found out two common problems on 95-newer S-1O,under the passenger side kick panel is a TCCM (transfer case control module)plug with 30 pins in the connector.Inspect for corrosion or broken wires.Mine was nice and clean.Second is a vacuum actuator in the center of the firewall in the engine compartment,two vacuum lines and a plug.One vacuum line was rotted off,cut and replaced,4WD started working right away.Good thing it snowed 20 inches yesterday.Thank you guys for your replies.

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