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Old 11-25-2011, 11:43 AM   #76
7T9Shark
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Re: 4wd system operation 98up Blazers

Wow, trans seals, TC seals, that's more possible bad news than I thought.

I'll check the trans fluid when I warm it up this afternoon. I also saw the hose routing on the driver's side of the trans, and it isn't as daunting as I thought. I may replace the hoses. When I pulled the hose off the actuator yesterday, it was dry. As soon as I figure out how to attach a photo, I'll send one of that other switch I was talking about.

In the mean time, R & R of the switch was a piece of cake.
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Old 11-25-2011, 11:47 AM   #77
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Re: 4wd system operation 98up Blazers

It is possible that after the switch is replaced and there isn't vacuum inside the transfer case, the seals might not leak, cross your fingers.
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Old 11-25-2011, 12:33 PM   #78
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Re: 4wd system operation 98up Blazers

Thanks for your help. I tried to attach the photo of that other switch I was talking about, but I think it's a mute point now that the trouble has been found.

You saved me tons of time, sanity and money.

snorander - if you're reading this, your help was much appreciated, too, as it put me on the path to the switch in the first place.

Cheers,

A. J.
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Old 11-25-2011, 04:49 PM   #79
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Re: 4wd system operation 98up Blazers

Glad there is at least partial success. Warm it up to operating temp and check the transmission fluid level. If the fluid level is not down noticeably, you probably caught it before it sucked fluid through the entire vacuum system. At any rate though, check those lines and clean/replace them as necessary. Then keep a close watch on the transmission and transfer case fluid levels and make sure they aren't leaking.
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Old 11-28-2011, 12:21 AM   #80
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Re: 4wd system operation 98up Blazers

I'm back. I still am having a heater/defrost issue.

1. No floor heat mode
2. When under a load, the heater switches from vent to defrost, becaue of low vacuum.


What I've done so far:

1. Tested the vacuum canister. No leacks
2. Tested the check valve. Works as it's supposed to
3. Tried to find the heat mode actuator under the dash, but gave up, due to impossible access

I hear no hissing in the dash.

HELP!!
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Old 11-28-2011, 03:34 PM   #81
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Re: 4wd system operation 98up Blazers

If the air flow changes to defrost on acceleration, (low vacuum) it's an indication of a vacuum leak either in the HVAC system, the 4WD system, or a faulty vacuum check valve. You'll need a hand held vacuum pump and some time and patience to find the leak. Start by applying vacuum to only one of the systems to determine which system is leaking. Then trace the line to locate and repair the leak.
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Old 11-28-2011, 09:57 PM   #82
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Re: 4wd system operation 98up Blazers

OK, one last question, then.....can you tell me where I can find the thread with instructions on how to remove the HVAC control panel from the dash, so I can check for oil contamination? In the mean time I WILL replace the hoses.

Thanks for your help.
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Old 02-28-2012, 02:04 PM   #83
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Re: 4wd system operation 98up Blazers

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Originally Posted by 7T9Shark View Post
OK, one last question, then.....can you tell me where I can find the thread with instructions on how to remove the HVAC control panel from the dash, so I can check for oil contamination? In the mean time I WILL replace the hoses.

Thanks for your help.

The dash comes apart pretty easy on these, a few screws & bolts, and it snaps right out, well that's how it is on my 2001. Should just be a couple of bolts to pull the hvac out once you remove the dash cover. Mine occasionally doesn't like to switch out of vent mode, it will after a while. At this point I just live with it. It doesn't happen that often so it doesn't bother me anymore LOL. Good luck Shark I know you can do it! Listen to Old_Master he is very wise when it comes to thses S-10's
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Old 09-21-2012, 01:06 PM   #84
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Re: 4wd system operation 98up Blazers

I have a 96 GMC Jimmy 4X4. I can shift into 4LO but not 4HI, the accuator engages the front axle and everything works fine in 2WD or 4LO. Can anyone explain to me why i can't go into 4HI?
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Old 11-09-2012, 07:19 PM   #85
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Question Re: 4wd system operation 98up Blazers

i have a 1999 s10 blazer 4x4 with the N1 (3 button)
the diaphram under the battery pulls the cable just fine
the 3 buttons (2hi, 4hi and 4lo) seem to work ok
they make noise when i do each one and the lights flash for a second then stay solid

4lo makes a louder noise then going to 4 hi or 2hi.

if i goto a dirt road and put the 4x4 into 4hi OR 4lo and put my brakes on and step on gas only my rear tires turn

my front dont

can someone help

thanks
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Old 11-10-2012, 07:45 AM   #86
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Re: 4wd system operation 98up Blazers


Welcome to the forum.
I think I can fix your problem in two simple steps.
1. Stop break torquing a 4wd vehicle. You're going to break stuff.
2. Go start your own thread in the proper location.
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Old 11-10-2012, 11:34 AM   #87
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Re: 4wd system operation 98up Blazers

Quote:
Originally Posted by JoulesWinfield View Post

Welcome to the forum.
I think I can fix your problem in two simple steps.
1. Stop break torquing a 4wd vehicle. You're going to break stuff.
2. Go start your own thread in the proper location.
first of all i do it on gravel
second of all this is the appropriate section
i read the whole 6 pages and there is all kinds of different questions to this thread
i believe mine is the most on topic
so i still waiting for help
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Old 01-02-2013, 03:52 PM   #88
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Re: 4wd system operation 98up Blazers

I have just bought a 98 blazer 4x4. the 4x4 was not working after reading the above articles & repalcing all the vacuum lines & cleaning the transfer vacauum switch. I was able to get it to lock in. when I put it in some mud I got stuck. The right front was spinning the left front was not. Is this the way it should work or do I have a problem with the left side locking?
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Old 01-02-2013, 06:20 PM   #89
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Re: 4wd system operation 98up Blazers

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Originally Posted by dccook View Post
when I put it in some mud I got stuck. The right front was spinning the left front was not. Is this the way it should work or do I have a problem with the left side locking?
Normal. The tire with the least amount of traction will spin. Only the right side locks to the differential when you select 4WD. The left side is always connected.
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Old 03-03-2013, 05:46 PM   #90
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Re: 4wd system operation 98up Blazers

Thanks muddog321. Great description.

My problem was that I couldn't shift into anything other than 2-high. Lights would flash, stop, and I'd be back in 2-high. Problem was the vacuum hose from the firewall vacuum switch to the actuator under the battery. Replaced the hose and I'm back in business. I couldn't have done it without you. Many thanks!
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