95 gmc suv 4x4 front wheel drv engagement

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Old 11-04-11, 03:47 PM
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95 gmc suv 4x4 front wheel drv engagement

there has to be an electric operated solenoid that opens and supplies vacuum to the vacuum pot which pulls the cable to engage the front wheels. I have been all over the net w/o success to find where that electric valve is located. HELP Tom
 
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Old 11-04-11, 03:56 PM
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Hi,

Do you have the buttons on the dash or the shift on the floor for the 4 wheel drive?

The actuator is under the battery tray on the shift models.

The button on the dash models have a motor on the front differential.

But there are a few other items that may be bad and need to be checked before digging in.

Make sure all vacuum hoses are good. Often they are dry rotted around the master cylinder. There is a canister type ball hanging on the drivers side hood? Check all hoses.

There are transfer case switches. Vacuum and electrical.

There is another switch for dash button 4x4 models. It down by the cap and rotor at the rear by the fire wall.

Let us know. There are several test you can do once we determine what type 4x4 you have.

How do I know all this? 96 chevy S10............

Mike NJ
 
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Old 11-04-11, 07:01 PM
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Thanks lawrosa
This is my first experience with 4wd. I helped my son several hours a today troubleshooting the problem.
Here is what we have learned. push buttons on the dash. vacuum actuator under the battery box which is cabled to the engagement plug. There is a two pin connector on the bullet that goes into the differential which I assume is a switch to indicate 4wd drive engagement. What bugs me as a mechanical minded person is that when you select the 4wd button that must send power to open a solenoid to put vacuum on the cable actuator pot. Where oh where is that solenoid that routes vacuum to the cable actuating pot. There has to be something to open and close vacuum to the actuator.
So far I have no luck in finding any internet site or person that can answer that question. I appreciate your help. Tom
 
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Old 11-04-11, 07:15 PM
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Old 11-04-11, 08:34 PM
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Its the vacuum switch in the transfer case. When the transfer switch engages it switches vacuum to the actuator which in turn pulls the fork that locks the front differential.

I will find you the site for trouble shooting, I have it somewhere. Also its a GMC Jimmy???? Blazer type thing?

And one more thing that may help. When you go to put it in 4 wheel or not in 4 wheel what are the lights doing on the 4x4 buttons? Blinking? On/off? etc...


Mike NJ
 
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Old 11-04-11, 09:20 PM
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Yes it is a Jimmy type thing. I don't know that much about the style, but I suppose it is of the chevy blazer type.
yes, there has been an issue with the dash lights turning on and off. Tom
 
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Old 11-04-11, 10:04 PM
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OK if you checked the vacuum hoses and your sure they are good then start at the switch on the dash. These go bad and may cause the 4x4 not to work.


If defective, your truck may not shift into 4WD and your shift light may not indicate 4WD when shifted to 4WD



When you do push the button and since you dont have the shift on the floor, there is a electric motor that engages the transfer case. You will need to make sure this is working. Its attached to the transfer case. You should be able to hear it whine when engaging.


If thats working and engaging then it trips the transfercase vacuum switch. This often is the culprint. It is screwed into the transfer case. When engaged this sends vacuum to the actuator under the battery tray. ( Check these vacuum hoses also. These are long and go to the fire wall. )

If defective, your shift light will not indicate 4WD when shifted to 4WD


Then the vacuum actuator itself. Make sure that the actuater is pulling in and the vacuum hose to this is intact. Often battery acid drips on this and dissolves the diaphram and vacuum hose. This pulls a cable to lock the front differential.


Next the cable itself gets worn out and they stick or break. This comes from the actuator and pulls a wishbone fork that locks the differential You can follow it there and disconnect it and make sure it moves when you try to engage 4 wheel drive. It dont move too much. I believe less then 1". But you will know if its broke. Its only one cable I believe. Pic shows two dont know why??

This Front Differential Shift Cable attaches on one end to the vacuum actuator and on the other end to the axle clutch shaft located in the front differential. It is a important piece of your 4WD system. Over time the cable becomes frayed and even snaps from being exposed to the elements. When this cable becomes inoperative, your front differential will not engage thus keeping you only in 2WD.




Last but not least a simple switch that activates the light to tell you your in 4 wheel drive and the front axle is locked. This is in the front differential. It has a two wire plug connector going to it. This does not affect the 4 wheel drive. Its just for the idiot light.


If defective, your shift light will not indicate 4WD when shifted to 4WD.

Hope this all helps and I hope you find it. Its fairly simple once you understand it all.

Good luck.

Mike NJ
 
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Old 11-05-11, 05:47 PM
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Lawrosa,
Well buddy you have put me onto something. I was grabbing for straws yesterday while working, as a result, I scanned the last reply that you sent, with valuable info that I overlooked at the first reading. Your last reply was more full of info than I had anticipated. If you look back to the beginning of my thread, you will see that I said there has to be an elec solenoid to allow vac to the actuator pot. I was dead wrong, there did not have to be an ELEC sol. I overlooked the fact that it could be a mechanically operated valve which after reading your last post, that is EXACTLY what it is and is opened to vac when the actuator fully engages the transfer case.
I will not be able to get back to the suv until next Saturday, but I am convinced that some sort of limit switch is at the end of the motor travel, which is needed to stop the motors travel and cut it off until the next command not allowing the transfer case motor to go that extra fraction of an inch to depress the mechanical switch.
From whgat I know now, and the fact that the motor will run, I believe we have a fix when we get back on it.
My only concern is that I have not seen the motor so do not know how difficult it will be to remove it and to access the plunger operated vac valve that it operates.
At this time I think you can credit yourself with the fix ad the only one to steer us to the problem.It is just getting back to it and of course being able to remove the motor without removing the front drive line, as I read in another article.
Thank you so much for your help. I will definitely let you know how we come out.
 
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Old 11-05-11, 06:18 PM
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when the actuator fully engages the transfer case
The actuator activate the fron differential, not the transfer case.

but I am convinced that some sort of limit switch is at the end of the motor travel
What motor are you talking about? The motor that engages the transfer case? Thats different then the vacuum actuator thats under the battery tray.


and cut it off until the next command not allowing the transfer case motor to go that extra fraction of an inch to depress the mechanical switch.
I would say it is fine and the vacuum switch is bad. Thats the cheapeast and most common failed part.

My only concern is that I have not seen the motor so do not know how difficult it will be to remove it and to access the plunger operated vac valve that it operates
I doubt its the motor and most likely the switch. These two parts are seperate and the mostor does not need to be removed unless its bad.

being able to remove the motor without removing the front drive line, as I read in another article.
Not sure about that. The part does look like the front shaft attaches to it.



Also read my post with the pics. I put it in basically its sequence of operations in order.

Good luck and let us know what you find. Hey gey a haynes repair manual. They help.

Mike NJ
 
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Old 11-08-11, 05:54 PM
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mike
I wrote when the actuator fully engages the transfer case.
I meant to say motor not actuator.
I hope that we will get a chance to use the info you sent in the pics Fri if my son is off.
You will be the first to know how it goes.
We would still be in the dark w/o your reply along with pics.
Thanks, Tom
 
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