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post #1 of (permalink) Old 12-19-2000, 09:42 AM
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im in big trouble

guys help me its been snowing and sleeting for about a week here in arkansas and my blazer was doing great and then all of the sudden it has stopped locking in to 4x4 it goes in to 4x4 and its really low geared but the front tires dont turn at all and i can figure it out so please help asap
thanks

Suck'n Gas & Haul'n Ass
~fight to keep public land open~
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post #2 of (permalink) Old 12-19-2000, 11:05 AM
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Re: im in big trouble

Hey I live in Arkansas too!! I live in heber springs but commute to Falcon jet in Little rock evrey day.
Anyway,I don't know if you year model has a fuse for the fourwheel drive or not.So check your fuse
box for that.Next is to look for some vacume hose lines,not sure where on your truck.But hope this
helps!

post #3 of (permalink) Old 12-19-2000, 11:10 AM
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Re: im in big trouble

Sounds like what happened to my 91 last winter! What was wrong with mine was the vacuum switch on the transfer case that applies vacuum to the vacuum actuator that locks the front diff into 4 wheel drive. Once you move the 4 wheel drive shifter into 4 wheel drive it actuates the vacuum switch to give vacuum to the front diff. actuator motor.

1991 S10 Blazer Tahoe 4x4. Edelbrook Headers, Holley 670cfm TBI, K/N filter charger, 30-9.5-15 tires, rebuild worked tranny
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post #4 of (permalink) Old 12-19-2000, 11:54 AM
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Re: im in big trouble

guys my blazer is a 88 and a lot of people have told me its the vacum switch on the transfer case and does anyone know how much and where to get on and if it is a dealer product or can i pick it of a a/z or oreliys thanks again

Suck'n Gas & Haul'n Ass
~fight to keep public land open~
post #5 of (permalink) Old 12-19-2000, 12:25 PM
 
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Re: im in big trouble

<font face="Comic Sans MS">Here is the part of the article I'm working on so far, yup it's copyrighted by me for now... haha [img]/wwwthreads_images/icons/wink.gif[/img] But anyhow, i haven't had a chance to test out the entire procedure on mine, but it should work ok for troubleshooting:

<blockquote><font size=1>In reply to:</font><hr>

Troubleshooting GM’s Vacuum Actuated Front Differential
by The_Sandman_454

Up to a certain point (which is noted at the appropriate location ), this file will work for any GM S/T series pickups that utilize a vacuum actuator to engage the front differential.

Step 1: Verify Vacuum Actuator’s operation
For this step you won’t need any tools. Open the hood, locate your vacuum actuator. If you are unsure of the location of the vacuum actuator on your truck, crawl under the truck, and locate the cable that runs to the front differential. It should either be on the passenger side fender, or under the battery tray on the passenger side, however yours may vary.

Now, have an assistant start the truck, and pull the transfer case lever (or press the appropriate button if you have an electronically shifted transfer case) into one of the 4 wheel drive positions (high or low), it shouldn’t matter which one. Observe the vacuum actuator.

If the vacuum actuator pulls the cable, your problem likely exists in the electric shift mechanism, the relay for it, or similar things (assuming you have an electrically shifting transfer case) or your transfer case shifter is out of adjustment. I do not know much of the intricate workings of the electric shift mechanism, and so I won’t be able to go into it any more than this.

If the vacuum actuator fails to pull the cable, proceed to the next step.

Step 2: Determine whether the transfer case actuator (or shifter) is actually engaging the front driveshaft.

If your vacuum actuator engaged the front differential, your problem is either the transfer case, or something inside the differential, the actual mechanism itself.

Step 2: Determine the Cause of the Vacuum Actuator not working.

Pull the cable by hand (in the direction of the rubber diaphragm) to ensure that the cable is not stuck in one position.

If the cable doesn’t move fairly easily (remember there should be a little tension), then there is likely either a problem with the cable itself, or a problem in the differential.



<hr></blockquote>



Sorry I didn't get back to you JR, but it didn't want to let me reply for some reason. Anywho, I'll let you know when that's about done...

---edited part here--- I don't know what I was thinking when I wrote that, it doesn't seem to make much sense, I'll try to dig up the updated file I had on my computer, the one that really does make sense, and post that. Sorry about that. But anyhow just make sure the actuator moves, make sure the vacuum lines to it are ok, make sure nothing is frozen in place because of the snow or ice, and the basic things like that, I'd say there's a very good chance that will help you solve your problem.

</font>

Tim
ORC Land Use columnist
My November article on ORC

http://www.off-road.com/land
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post #6 of (permalink) Old 12-19-2000, 02:28 PM
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Re: im in big trouble

MINE DID THE SAME THINK AND ALL IT WAS WAS A VACUUM LINE BURN IN HALF
HOPE THIS HELPS

post #7 of (permalink) Old 12-19-2000, 08:13 PM
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Re: im in big trouble

All you have to do is to unhook the vacuum line from the vacuum actuator and run a new line from the vacuum actuator to the TbI or any vacuum line with vacuum and just tee the new line in. This will make the front diff be engaged all the time. This is just a temporery fix!! I had to buy a new one for my S10 last year it was about 20 bucks from the dealer. It's an dealer item only!

1991 S10 Blazer Tahoe 4x4. Edelbrook Headers, Holley 670cfm TBI, K/N filter charger, 30-9.5-15 tires, rebuild worked tranny
post #8 of (permalink) Old 12-20-2000, 05:06 PM
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Re: im in big trouble

I got my truck for $1500 less because that little vacuum valve. The 4WD didn't work so I told him it could cost a lot to fix. I knew what it was. Its a $25 part that you can get at any Chevy dealer. It takes 5 minutes to change. I would check your vacuum lines going to the valve but that is a common problem with these trucks.

post #9 of (permalink) Old 12-20-2000, 06:14 PM
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Re: im in big trouble

You can either replace the switch and/or vacuum lines or get the Posi-Lock system from JCWhitney. It uses a cable that attaches to the cable on the vacuum actuator under the hood to "lock" your 4wd. Its pretty much guaranteed to always work. Its just one little thing extra you do to put it in 4wd. Just pull on the cable(its got a knob similar to a hood release knob) and shift the 4wd shifter. And you never have to worry about the vacuum system again. But its $120... I bought it and am waiting on it...in the middle of the snow....go figure...

Mark

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