[JakeX39]

Hello Everyone,
I have a 2006 GMC Sierra 1500 with the 5.3 engine and I just got it off of marketplace about a month ago. I went off roading with some friends and got stuck. I tried turning on to four low and then to four high and back, but my front wheels were not spinning at all. I was in neutral and stationary when trying to go in 4WD.
In this moment I heard the front diff make a loud “click” or shift when pressing the four high or four low but still the front wheels were not moving, so I thought: “Okay, it must be locked in, so I should be good to go.” But it didn’t work…
Some are telling me it’s my actuator making my 4WD not work but could it still make that sound? Also, is that “click” or shifting sound coming from the Transfer Case Encoder? This is my first GM ever so please be blunt and give me whatever questions or suggestions you may have. Thank you

 

[davester3500]

Shift in 4hi.
Drive forward a few feet
park
lift up one front wheel
try spinning it

If the wheel doesn't spin, great, you are in 4wd mode and it's working. You might repeat for 4lo, but it should also work.

If the wheel does spin, then reach under the driver's side of hte truck and manually try spinning the front driveshaft. Report if you can spin the front driveshaft, and if it also spins the front wheel or not.

 

[JakeX39]

Okay will do thank you so much

 

[JakeX39]

Okay, I did that procedure. I drove a few feet in 4HI and then jacked up the driver side front wheel. The wheel spun, but when trying to spin the driveshaft it would not.

 

[davester3500]

Then the transfer case is shifting into 4wd mode, but the front differential isn't getting locked.

There's a ball switch in the transfer case, that switches to indicate 2 or 4wd mode, wired to an actuator that screws into the front diff. When activated (switching to 4wd mode), the actuator extends itself, pushing a sliding gear, to connect the passenger side wheel to the differential (this happens inside the passenger side of the front axle housing), and then the front axle behaves as a normal axle w an open differential.

charm.li will have a diagnostic procedure and connector pinout, so you can test if the actuator is getting signalled from the transfer case to extended/retract.

You can also lift the passenger side front wheel up a bit, unscrew the actuator from the front diff (a little bit of diff fluid may come out, put a container under it to catch the oil), then use something like a screwdriver, short wood dowel or steel rod, stick it in the opening to manually lock the front diff (need to push it about an inch or so) and then try spinning the passenger side wheel. If you've locked it, the wheel either won't spin (if the TC is in 4wd mod), or it will be hard to spin, and the front driveshaft will also spin (if the TC is in 2wd mode).

 

[JakeX39]

I put in a new actuator because the old one was bad. Now I tested the 4wd and the front driveshaft is spinning and I hear the actuator but the front wheels still don’t spin. I’m confused.

 

[davester3500]

I would suggesting off with repeating the above process, to verify that the front diff isn't locking in 4wd mode.

You threw a new actuator for the front diff at the truck? If so, perhaps unscrew the actuator so it's removed from the housing, plug it into the wiring harness (while it's still unscrewed), then shift between 2 and 4wd modes. This can be messy, as oil can come out of the diff and you may need to move the vehicle a bit for the shift to happen.

When it's shifted, see if the actuator has extended (for going into a 4wd mode), or retracted (for 2wd).

If the actuator is moving in/out as you shift modes, then something is busted in the front diff.
If the actuator isn't moving, then either there is some electrical problem or the new actuator is bad.

 

[JakeX39]

I’ve done some online research and I’m being pointed towards a bad shifter fork or actuator fork within the front differential. Would that be a cause for this problem?

 

[davester3500]

first find out if the actuator is actually working or not.

 

[Back in Black]

I had a similar problem with a Chevy Colorado that had seen a lot of 4wd use. Nobody could offer any suggestions. The transfer case was working correctly, and the actuator was getting a signal and extending when it was supposed to. But the front would not lock up. So, I completely disassembled the front differential/axle and discovered the problem. Where the two axles come together and are connected by the sliding gear (as you called it) the two axles are supported inside the housing by needle bearings. These needle bearings had worn out and the axles were "drooping down" so that the sliding sleeve (that's what I call it) couldn't successfully slide over the driver's side axle. I replaced these needle bearings and also ground the inside of this sliding sleeve to be a little bit funnel shaped to help if the needle bearings ever wore out again.
It was all very new and mysterious to me, but once I got into it, it reminded me of many hours of working on old outboard motors and the way the lower unit of an outboard motor shifts from forward to reverse! (that's where I got the term "sliding sleeve") If you're familiar what that, this will be a "lightbulb going off in your head" moment for you. If not, you'll think I'm a crazy old man!
Either way, if your transfer case is working and the front axle isn't locking up, even though the actuator works correctly when removed and the wires connected, I bet this is your problem.

 

[JakeX39]

I had a similar problem with a Chevy Colorado that had seen a lot of 4wd use. Nobody could offer any suggestions. The transfer case was working correctly, and the actuator was getting a signal and extending when it was supposed to. But the front would not lock up. So, I completely disassembled the front differential/axle and discovered the problem. Where the two axles come together and are connected by the sliding gear (as you called it) the two axles are supported inside the housing by needle bearings. These needle bearings had worn out and the axles were "drooping down" so that the sliding sleeve (that's what I call it) couldn't successfully slide over the driver's side axle. I replaced these needle bearings and also ground the inside of this sliding sleeve to be a little bit funnel shaped to help if the needle bearings ever wore out again.
It was all very new and mysterious to me, but once I got into it, it reminded me of many hours of working on old outboard motors and the way the lower unit of an outboard motor shifts from forward to reverse! (that's where I got the term "sliding sleeve") If you're familiar what that, this will be a "lightbulb going off in your head" moment for you. If not, you'll think I'm a crazy old man!
Either way, if your transfer case is working and the front axle isn't locking up, even though the actuator works correctly when removed and the wires connected, I bet this is your problem.

Lol, I know exactly what you’re talking about. But thankfully it wasn’t needle bearings, instead, it was the retainer clip within the front axle shaft. It was entirely mangled.