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Discussion Starter #1
Clicks from under truck when I push the 4X4 hi button, but doesn't engage the 4wd. What's most likely to be the problem? Too cold now to slide under there! Not long ago I had 4wd engaged while turning sharp in reverse on dry concrete. Think that may have been the last time it worked, not sure
 

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First and easiest thing to check is the front axle actuator. It's on the front of the front differential and is plastic and has wired going to it. Unplug the wires, unscrew it with a large pair of channel lock pliers and have someone put the truck in 4WD. There should be a plunger that comes out of the end. That locks the front wheels together. If that is working correctly, you're back to the transfer case. Check the 4WD module under the driver's seat to make sure connections are good. Clean them up if necessary. If all that looks good and the fuses and relays are all good, I'd start googling and see what someone who knows more than me can recommend.
 

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Discussion Starter #3
So I take it the front axle actuator is a differential lock. Even if that weren't working, wouldn't the transfer case shift into the selected 4WD mode. You'd just have an operating differential on the front axle?
 

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No. Until the front axle actuator locks the left and right wheel together, you don't have 4x4. I know that doesn't make sense, but there are very lengthy, very technical videos out there that explain the principle of how the front differential works and it makes sense if you watch them, but I can't explain it briefly. If you jack up all 4 wheels and put the truck in 4hi, if the front driveshaft spins, the transfer case is working. If the front driveshaft turns, but the front wheels don't turn, you have a front axle actuator problem. On my truck, the transfer case was fine and when I bench tested the front axle actuator, it was fine too, but I did not have 4 wheel drive. Inside the front axle extension tube (on the driver's side of the differential) There was a set of needle bearings that were worn out and it would not allow the front axle actuator to lock the two front wheels together. Inside that axle tube, there are two splined shafts and a collar that slides over them to lock them together. The bearings were worn out and the two pieces did not line up correctly, so the left and right wheels remained independent of each other. So, in 4WD, the front driveshaft would turn, but the front wheels would not. Also, until the transfer case engages, and the front axle actuator engages, the 4WD light will continue to blink. Both the transfer case and the front axle actuator have internal switches that send a signal when they are fully engaged. The front axle actuator has 4 pins on the plug. You have 12v (top left), ground (bottom left), signal ground (This activates the actuator when grounded )(center) , and one of the other pins sends a signal when the actuator is completely extended and activated to make the lights stop blinking. On my truck, when the front axle actuator was installed it was not able to extend completely because the collar was not able to move into place, so the light continued to blink. When I removed the axle actuator, but left it plugged in, and put the truck in 4WD, the transfer case worked and the axle actuator worked and the lights worked correctly, indicating that the truck was in 4WD.
I'm sure the transfer case has the same set-up so that if it is not fully engaged and the the shift motor isn't moving all the way to it's intended position, the light will continue to blink.
 

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Discussion Starter #5
Thanks. Makes good sense to me. I have some things to try, especially the one guy's post about how to get into 4wd even if the actuator isn't working. Has too with attempting to engage 4wd, then putting trans in N or P and shut the engine off. Then when restarted it will be in 4WD, even though the push button indicators don't say so.
 

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Discussion Starter #6
Thanks. Makes good sense to me. I have some things to try, especially the one guy's (parts_guy) post in a difference thread about how to get into 4wd even if the actuator isn't working. Has too with attempting to engage 4wd, then putting trans in N or P and shut the engine off. Then when restarted it will be in 4WD, even though the push button indicator doesn't say so.
That worked, attempting to engage whine in N pr P, then shutting key off. The nupon restarting I found it was in 4wd hi, as desired, even though that button was still flashing. On the first try it went right back into 2wd when that button was pushed. Second try took some fiddling around with buttons transmission gear etc, but finally it did go back into 2wd. I had that LF axle seal replaced about a year ago, but see it's leaking a little again now. Bet I know why - the bearing is bad.
 

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Discussion Starter #7
So I disconnected the wiring and took the front axle actuator out. The plunger is retracted. Then I plugged the actuator back in and pushed the 4WD button, nothing happened with the actuator. I want to test it to see if the actuator is at fault, or if the problem lies with it not getting signal or power. The connector has green, black. black/white and reddish-orange leads. Which are the power wires that I could connect directly to 12 volt to see it it's working, and/or I could connect a test light to the connector and see it it's got power to it when the button is pushed?
 

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I made a very sharp turn on concrete once not realizing my 4x4 was engaged and I had trouble getting it to disengage. It took several times of forward and reverse and engine turn off and restart to reset something. That's when I found out really sharp turns are bad for 4x4.
 

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Discussion Starter #9
Well, I've wondered about that too. However, it seems the problem I'm having with mine in in the electric control system for the front axle. Unfortunately that could involve the ignition switch, the 4X4 control buttons on the dash, the controller on the transfer case, as well as some other components too I suppose. My old electronic diagnostic code reader shows no codes. I wonder if the newer, more sophisticated and pricy ones might detect the problem.
 
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