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Old 09-03-2012, 10:24 AM   #1
K5_Fla
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2002 Silverado Z71 - 4x4 not working

I have a 2002 Silverado and the 4x4 isn’t working. I push the button and the 4x4 switch blinks for a few second and you can hear (and feel) the actuator click in below. Then it lights up in the proper 4x4 mode just like it should. All indications appear that it’s working… but it’s not. No service 4x4 codes or anything. Another thing… I turned the front drive shaft by hand… spins freely in 2hi like it should. Switched to 4L and the driveshaft locks down like it should. Again… everything seems to be working… just isn’t. I didn’t find out until yesterday when I got stuck… and couldn’t ever get 4x4 to work. Sucks because I was barley stuck and would have pulled right out if I had 4x4.


What should I check? Also the ABS light is on in the truck…has been for a longwhile. I read somewhere that this can cause the 4x4 not to lock in ?? True? anyway to override the ABS?
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Old 09-03-2012, 10:37 AM   #2
jake 03
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More than likely its the front axle actuator or the wiring to it,could be something mechanically wrong with the axle but I would put money on the actuator.

Edit. Abs will not cause the 4wd to not work. Check the grounds on the frame under the drivers door. A poor connection there is a common cause of abs light illumination.
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Old 09-03-2012, 11:56 AM   #3
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Not exactly sure what you meant about the driveshaft....
Never mind, reread it and I understand now.
There are two things that have to work for you to have 4wd. The shifter on the transfer case is working, because the driveshaft locks.

The other is the actuator on the right front axle. I think that they are still using the boiling fluid system.
There is a cylinder mounted on the shifter on the axle tube that has a liquid in it. When you shift to 4wd, a heater boils the liquid and the pressure causes a shaft to slide out and push the shifter yoke over to engage the right axle.

The problem with what you said, is that on most models I remember, there is a switch on that shifter that turns on the 4X4 light when the shifter moves.

On all my friend's trucks, I always tell them to wait for the light because it takes a few seconds for the fluid to boil.
The colder the weather, the longer it takes.
Also, if you switch the truck off, the power to the cylinder goes off and it shifts the axle out of 4wd, so you have to wait a few seconds for the fluid to boil again after you crank up.

If they do not have the switch on the axle anymore, then its probably a bad cylinder or the wire is loose or bad.

If they do have the switch, then the shifter moved, but did not engage the axle for some reason.

Either way, the test is simple.
Jack up the right front, Take that cylinder off, and push the shifter in by hand and see if the axle engages.
If you see where any liquid has leaked out the cylinder, there is no need to test it. Otherwise, you can put 12 volts to it and see if the plunger moves out.

If its bad, which is the most common thing, you have two choices. Replace the cylinder, or go to the conversion that Warn makes.
It replaces the cylinder with a piece that has a actuator cable.
You run the cable into the cab, and it works like a choke cable.
Just pull or push a knob to move the shifter.

Lots of folks don't like that and want to stay stock. Personally, I like the more positive system.
I have helped install the kit on two different trucks.
The first one was when it failed in the swamp, then a couple of years later the same guy bought a new truck, and we put a kit on the next day.

He did not want to have to get pulled out again.


Of course, all these were several years ago, so they may have modified the system in 2002.
If so, I'm sure someone here will chime in.

But its fairly obvious, just slide under and look at the shifter on the passenger side axle tube.
If its not the cylinder, and its getting power, I have heard of some cases where the bushing or bearing the supports the right front axle on the shifter end wearing to the point that the shifter does not line up right any more.

But you should be able to tell that when you try to shift it by hand.
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Old 09-03-2012, 04:12 PM
Posted in reply to Fordum's post starting "Not exactly sure what you meant about..."
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Its possibly the actuator. it should be an electronic one. put a jumper in theactuators connector then push ur 4x4 buttons they should stay on if it was a bad actuator. at least that's how i tested a 97 once.
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Old 09-03-2012, 07:22 PM   #5
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Fordrum, they stopped using the thermal actuation mid 90s. It is an electronic actuator.

OP, Jack one front tire of the truck up, engage 4wd, and spin that tire thats in the air. If the drive shaft spins, its the actuator on the case. If the shaft doesnt spin, its the actuator on the front end.
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Old 09-03-2012, 08:27 PM
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plyr2k - Pm sent.. thanks
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Old 09-03-2012, 08:55 PM
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Quote:
Originally Posted by plyr2k View Post
Fordrum, they stopped using the thermal actuation mid 90s. It is an electronic actuator.

OP, Jack one front tire of the truck up, engage 4wd, and spin that tire thats in the air. If the drive shaft spins, its the actuator on the case. If the shaft doesnt spin, its the actuator on the front end.

I thought they had changed to something else, but I did not remember what.
Still right side only though, right?

Never have quite understood that. Way back when, it was always said that if one hub did not disengage, it would burn up the front end from the spider gears spinning constantly.

Then they came up with a design that only disengages one side.......
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Old 09-04-2012, 10:59 AM
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Some updates –

front axle actuator is working - I removed it and tested… when I put in 4x4 mode the thing extends out and gets a boner like it should.

Jacked up one tire up front - out in 4hi and turned the tire by hand… the front axle turns like it should.
Axle seems all good.

Thinking the issue is with the transfer case motor - http://www.summitracing.com/parts/RNB-600-901/
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Old 09-04-2012, 06:24 PM
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Quote:
Originally Posted by K5_Fla View Post
Some updates –

front axle actuator is working - I removed it and tested… when I put in 4x4 mode the thing extends out and gets a boner like it should.

Jacked up one tire up front - out in 4hi and turned the tire by hand… the front axle turns like it should.
Axle seems all good.

Thinking the issue is with the transfer case motor - http://www.summitracing.com/parts/RNB-600-901/
For future reference, when the front end actuator isnt working as it should the 4 wheel drive light will flash when its shifted. The case will shift, but the front wont engage.

A former friend of mine worked at a dealership. He said the encoder motors rarely go bad, its usually an internal problem with the case. Will the case shift into low?
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Old 09-04-2012, 06:30 PM
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K5_Fla
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yes, the case does shift in 4L ( and I have low range) ... just dont have the 4x4
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