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Username Post: 99 blazer 4X4        (Topic#253876)
NathanC 
Forum Newbie
Posts: 9

Reg: 12-05-10
12-05-10 07:19 PM - Post#2014065    

I have checked the acuator under the battery and its not geting vacuume the acuator seems in good shape. Is my next step to replace the vacuume switch on the transfer case?

 
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Chevytech 
Subject Matter Expert - Senior Member
Posts: 3014

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
12-05-10 07:27 PM - Post#2014068    
    In response to NathanC

Looking for an exploded view of the 4x4 parts for these little trucks I ran across information that starting in 1999 there is no longer a vacuum switch on the transfer-case.

On 1999 & newer S/T-10 trucks the vacuum to the front axle actuator is controlled by a solenoid mounted on the firewall instead of a switch on the transfer-case.

I will do some digging to see if I can verify that information. You could follow the vacuum hose back from the actuator and see if it leads to a solenoid on the firewall.

I also need to see if the TCCM controls the solenoid.

Here is a photo of what it may look like:
http://kylestubbins.com/files/blazer_vacuum_s witch...
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3014

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
12-05-10 07:58 PM - Post#2014085    
    In response to NathanC

Does your truck have "Autotrac"?

It looks like it is the 236 Autotac transfercase that uses the solenoid on the firewall.

See if your truck has this part:

http://img.photobucket.com/albums/v97/Jigg1300/B la...
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
Auto Tech 
Contributor
Posts: 109

Age: 45
Loc: midwest
Reg: 01-18-10
12-05-10 09:23 PM - Post#2014115    
    In response to Chevytech

I had a 99 but it just had the 3 push button 4wd. It had a vac switch I think. My sister had a 2000 and it had the auto 4wd and if you would tap on the solenoid you are talking about on the firewall it would start working.
Nothing makes someone more productive than the last minute.


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3014

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
12-06-10 08:52 AM - Post#2014227    
    In response to Auto Tech

  • Auto Tech Said:
I had a 99 but it just had the 3 push button 4wd. It had a vac switch I think. My sister had a 2000 and it had the auto 4wd and if you would tap on the solenoid you are talking about on the firewall it would start working.


Thanks for the input!

I have read that about tapping on the solenoid elsewhere too.

It seems that many control parts that air gets sucked through eventually get dirt inside to the point it cause problems.
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
NathanC 
Forum Newbie
Posts: 9

Reg: 12-05-10
12-06-10 05:20 PM - Post#2014404    
    In response to Chevytech

Its not the auto 4wd its the 3 push button 4wd. So I guess Im looking for a vac switch? Thats going to be on the tranfer case? Ill prob still have to follow the vacuume hose to find it.

 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3014

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
12-06-10 06:01 PM - Post#2014414    
    In response to NathanC

Unplug the vacuum switch and make sure vacuum is getting to it.

If there is vacuum at the t-case switch, and the transfer-case shifts ok, the hoses aren’t leaking, and vacuum does not get to the front actuator, then it all points to the switch. The vacuum switch is a VERY common failure item.

The vacuum switch is #46 on this illustration:


Source;
http://www.rsgear.com/products/ep-diagrams/ images/...
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3014

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
12-06-10 06:06 PM - Post#2014417    
    In response to NathanC

Here is what the bottom of the switch looks like when you get it out.



source:
http://images.whisystems.com/smartpages/partinfo_r ...
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
NathanC 
Forum Newbie
Posts: 9

Reg: 12-05-10
12-07-10 03:24 PM - Post#2014846    
    In response to Chevytech

I found the switch it had been unplugged and one of the vacuume lines was pluged with a small bolt. I took the bolt out and plugged it back into the switch 4wd still didnt work of course. I orderd a switch that will be here tomorrow.

 
gchemist 
Senior Chevytalk Moderator
Posts: 21985
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
12-07-10 05:40 PM - Post#2014900    
    In response to NathanC

Nice work. Hopefully the new switch will put back in 4X4.
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3014

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
12-07-10 05:43 PM - Post#2014902    
    In response to NathanC

If once you get the new vacuum switch installed, if the front axle says engaged, after you shift back to two wheel drive, someone could have done what you found because of this.

There is a vent hose for the transfer case switch that is located under the hood. People find this vent hose and think it fell off something so they either plug it, or connect in to a vacuum source which will cause the front axle to say engaged in two wheel drive.
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
NathanC 
Forum Newbie
Posts: 9

Reg: 12-05-10
12-08-10 04:21 PM - Post#2015312    
    In response to Chevytech

got the switch changed and still no 4wd. Visually confirmed the actuator under the battery working. I put the truck back in two wheel drive and theres a clicking sound coming from the front end of the truck. So plugged the vacuume hose back up like they had it and sound stopped.

 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3014

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
12-08-10 05:13 PM - Post#2015330    
    In response to NathanC

  • Quote:
got the switch changed and still no 4wd. Visually confirmed the actuator under the battery working.

Then you made progress.

  • Quote:
I put the truck back in two wheel drive and theres a clicking sound coming from the front end of the truck. So plugged the vacuume hose back up like they had it and sound stopped.

A clicking sound from the TCCM is normal. It is usually mounted under the right hand kick panel.

Whenever the electric-shift motor is activated, the motor and the electrical circuits are tested both in the de-energized and energized condition.

If the vacuum switch supplied vacuum to the front axle, the transfer-case was in 4WD.

If it did not set a new trouble code everything was probably good, until you disconnected and plugged it again.
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
NathanC 
Forum Newbie
Posts: 9

Reg: 12-05-10
12-09-10 04:49 PM - Post#2015781    
    In response to Chevytech

when i get to about 20 mph the clicking turns into more of a howling noise sounds like bearrings going out but when its in 4wd the sound stops but the front wheels not pulling in 4wd. I really appreciate your help.

 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3014

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
12-09-10 05:54 PM - Post#2015816    
    In response to NathanC

I did not understand that the clicking was with vehicle movement. I thought you may be hearing the TCCM click.

The previous owner could have severely damaged the front axle and that is why it was made so it would not engage.

When in two wheel drive the ring & pinion, carrier, and side bearings do not move. In 4WD they do.
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
NathanC 
Forum Newbie
Posts: 9

Reg: 12-05-10
12-09-10 06:03 PM - Post#2015828    
    In response to Chevytech

Yes I think you are right i think ill take it to the shop. I want to thank you guys for all the help I could have never got this far by myself.You guys are awesome!!

 
NathanC 
Forum Newbie
Posts: 9

Reg: 12-05-10
12-22-10 02:42 PM - Post#2021502    
    In response to NathanC

Good news mechanic told me to bring truck over before I bought a front differentail so I did and he unsscrewed where the cable goes into the differential. He worked it in and out then screwed it back in. Now 4wd drive started working and no noise! The only problem now is its just a little hard to get back in 2wd I have to back up a few feet. Thanks again for saving me a bundle!

 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3014

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
12-22-10 04:10 PM - Post#2021539    
    In response to NathanC

You’re welcome, but I still think your truck needs more work.

There is a spring in the front axle that should be able to move it to the two wheel drive position by spring pressure.

There is a washer that can get damaged if the right front axles is pulled out and pushed back in. That washer could be getting the way so the axle is having trouble shifting because it is hitting the edge of the washer.

I don’t have a photo link for a little truck but here is a photo of washer damage on a full size truck. The position of the washer in this photo would totally prevent a shift to 4WD.

http://img291.imageshack.us/img291/9994/dscf0001b....


Photo Source:
http://www.chevytalk.org/fusionbb/showpost.php?pos...

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
NathanC 
Forum Newbie
Posts: 9

Reg: 12-05-10
01-25-11 06:41 PM - Post#2037268    
    In response to Chevytech

4wd worked fine for a whil but now I am having trouble getin the thing out of 4wd changes to 4low and 4hi fine its just real hard to get back into 2wd

 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3014

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
01-26-11 08:18 AM - Post#2037520    
    In response to NathanC

I am not surprised the vehicle is having problems.

My best guess is the shim/washer in the front axle is damaged and getting in the way making it bind. It takes spring pressure to return it to 2WD. If it binds the front axle will tend to stay engaged.
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
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