Center Diff Won't Disengage (1 Viewer)

[wildpaths]

I have a 2001 LC100. This vehicle is well-known to this form though I am not. I was lucky enough to become the owner of the LC that is well-detailed in this historical thread: The Road to a 100 and 2001 build thread

At the moment the Center Differential (CD) will not disengage. The CD and VSC OFF amber lights on the dashboard are ON, as would be expected with the CD locked. When I push the button, I can hear the relay buzz behind the glove box, and I can hear the CD actuator working under the car. These sounds occur reliably when the button is pressed IN to LOCK, and when the button is pressed AGAIN (out) to UNLOCK. Whatever happens with the button, the CD and VSC OFF lights remain ON.

I am 100% sure that the CD is locked, and it is not a problem with the light staying on. I know this because the FRONT driveshaft is removed from the vehicle and I am still able to drive. If the CD was not locked, the vehicle would not move.

To support full problem solving, you should probably have the backstory explaining why I have the front driveshaft removed.

Over the weekend, the wife, dogs, and I went on a Sunday Drive up the 395 to Independence for some hiking and picnicking. I figured if I brought all the food, water, and gas we needed, and didn't stop at any local businesses, we would endanger the locals, and could get a little sanity. It was a beautiful day and a nice drive on 15 miles or so of dirt. My wife doesn't have much dirt driving confidence (despite her skill) so she drove the way out. Often when this is going on, I manage the transmission and traction control so she can focus on the dirt road. In one particularly nasty stream bed I hit the CD button and the CD and VSC OFF lights came on, as usual. I don't remember if the VSC TRAC came on at that time. I left this on since we were on dirt. About 8 miles later, when we left the dirt, I hit the CD button and nothing happened. At this time I noticed that the VSC TRAC amber light was ON.

We verified that the CD was indeed locked by doing a tight turn and feeling the tires chirp and leave black marks on the road. We did some backing up and turning but no success. We decided to coast a few miles downhill in NEUTRAL to Lone Pine so we could get signal and evaluate our options.

At this point we followed the normal advice, lots of backing up, going forward, and turning. No success. We figured maybe we needed dirt, so we did 6 miles on highway at 40 MPH to get to some dirt and drove around a bit, doing doughnuts and figure eights both forward and in reverse. No success.

It was getting dark, so we made some dinner and camped out. The canned food I keep in the rig and the RTT paid off. We woke to a beautiful sunrise on Mt Whitney, made coffee, and then drove a bit more. CD still locked. At this point we did listen for the RELAY. We could hear the light buzz of the RELAY but we did not hear the ACTUATOR moving. SO we drove close enough to town to get signal in case we needed a tow truck. We didn't want a tow, to avoid COVID exposure. So I crawled underneath and removed the front driveshaft.

With the front driveshaft removed, and the CD locked, the LC drove like a dream. I will note here that the CD, VSC OFF, and VSC TRAC lights were ON the whole time. We did not dare hit the CD button again for fear it would actually disengage and require reassembly of the driveshaft. We made it home safe and sound Monday AM.

Now, Tuesday PM, I decided I had learned enough from the forums to start looking at the problem, expecting I would be diagnosing electrical issues. But I found the new condition instead. CD still locked, but now the VSC TRAC light stays OFF and I can hear the ACTUATOR working in addition to the RELAY.

As a little more background, I know from last months trip to Baja that a vigorous splashy puddle crossing will cause the VSC TRAC and VSC OFF lights to come on in my rig. This indicates to me that there is some electrical connection issue in this circuit that needs to be addressed, and is a possible cause for the ACTUATOR not working when the VSC TRAC light was ON, and the ACTUATOR working now that the VSC TRAC light is OFF.

But right now, the ACTUATOR is making noise as if it is working.

I have two guesses:

#1: Now that the ACTUATOR is working, I should do a lot of forward/reverse to see if the CD will disengage.

#2: Something is physically broken inside the ACTUATOR, much like in this post: Center Diff Lock Actuator

I would love to hear thoughts on this, and hopefully some simple fix.

 

[nukegoat]

Sounds like you need to take it apart

 

[wildpaths]

I gave a shot at taking it apart and failed. I removed the cross-member bolts and lowered the Transfer Case (TC) with a jack. I removed the 4 bolts holding the CD actuator to the TC. The CD actuator wouldn't budge. Eventually was able to pop it loose, but only the passenger side moved, providing a 5mm gap. The driver's side of the CD actuator didn't move, so it was askew. It wouldn't move any more.

I suspect this is because the CD was still locked. Luckily, I was able to bolt it all back together so the truck can still drive. But I suspect I can;t get that CD actuator off unless I can get it to unlock.

Again, it is getting power and responding to the CD switch with good whirs and vibrations. It just is not unlocking. All I can think off is some aggressive driving around with the CD switch off hoping it disengages, and then be prepared to reinstall the front driveshaft in the field to get it moving again.

Unfortunately, I live in a flat area with no dirt. Maybe its time for a field trip?

Any other suggestions?

 

[saucebox]

I just had mine apart as well, with the opposite problem (no engagement). Locked or unlocked, the actuator should come off. It takes some prying—you have to get past the RTV that seals it up.

The actuator just moves a gear inside the transfer case from north (unlocked) to south (locked). The little gear in the transfer case can be lifted out by just picking it up. There shouldn't be anything binding the actuator beyond the RTV. But the space is tight and vision impossible up there—maybe give it another shot.

 

[wildpaths]

Thanks for the info. I hadn't been able to find a picture of what the bottom of the actuator looks like. I was able to find a good picture on eBay, and you are 100% correct. There should be only a little gear on the bottom, that drives a larger gear.

I don't understand why I couldn't get it all the way off. I got the passenger side to lift 5mm and stay open, but the driver side wouldn't move. Kinda like a clam shell. I was afraid to get too medieval on it, and the space up there is limited with few ways to apply force.

These pictures give me some confidence to try again.

 

[wildpaths]

I've got a spare in my truck. Quick as I can get out of a Zoom, I'll get a photo of it for you, so you can see how everything connects.

Wait... You keep a spare CD actuator in your truck? Do these things break often enough that this is worth carrying around?

 

[saucebox]

Wait... You keep a spare CD actuator in your truck? Do these things break often enough that this is worth carrying around?

Hah, no. I couldn't get mine to engage at all, so I assumed the actuator was broken and sourced a spare before tearing into it. Waste of money.

Turns out someone had been in there before, and just didn't put the motor back together properly. The actuator should be in the locked position on install, and the smaller loose gear (in your picture above) pushed as far south as it can go (also in the locked position). I jacked up the passenger side rear on mine, and could turn the tire with my foot while pushing on the gear until I felt it was locked.

 

[wildpaths]

Hah, no. I couldn't get mine to engage at all, so I assumed the actuator was broken and sourced a spare before tearing into it. Waste of money.

Turns out someone had been in there before, and just didn't put the motor back together properly. The actuator should be in the locked position on install, and the smaller loose gear (in your picture above) pushed as far south as it can go (also in the locked position). I jacked up the passenger side rear on mine, and could turn the tire with my foot while pushing on the gear until I felt it was locked.

Glad to hear that this doesn't fail often. That fits with my internet research on this.

I took advantage of the warm day, and working at home to give the underside area around the transfer case a good wash-down before I go for a second try at removing the actuator.

If you answer a few questions, Saucebox, it might be helpful.

1) Which directions are south/north when you refer to the vehicle?
2) If it turns out my actuator is actually broken, would you be interested in selling your "spare"?

Thanks!

 

[saucebox]

Ah, of course. North towards the front, south is the back.

And yeah, you bet. The one on my truck now is basically brand new (that I could tell anyway), so I'll likely never need it. I could probably get it out tomorrow if you just want to have a spare on hand—just send it back if you end up not needing it.

I'd think if yours actually is broken, you could reassemble in the unlocked state and be fine. Mine was installed wrong for...no idea how long, and everything still looked great.

 

[wildpaths]

Ah, of course. North towards the front, south is the back.

And yeah, you bet. The one on my truck now is basically brand new (that I could tell anyway), so I'll likely never need it. I could probably get it out tomorrow if you just want to have a spare on hand—just send it back if you end up not needing it.

I'd think if yours actually is broken, you could reassemble in the unlocked state and be fine. Mine was installed wrong for...no idea how long, and everything still looked great.

I will try again tonight. (and I messaged you about the spare)

I don't understand how to manually leave it in an unlocked state for reassembly. It's already stuck in a locked position and won't come unlocked, and I have no idea how I would unlock it with my fingers.

Any advice?

 

[wildpaths]

Update: Definitely a broken actuator.

I got the actuator off. Had a friend hit the switch while I looked from under the rig and saw the gear turn. But it didn't turn much. It only turned less than a quarter turn.

I pulled it apart and found a broken arm inside. This is exactly what was found in this 2006 post by Greg B: Center Diff Lock Actuator.

The failures are not just similar, they are almost identical - it's freaky! The fracture line is almost identical, and the way the broken part jammed between the broken arm and the other arm is almost identical. So weird!

I am so happy that I found the problem, and that the problem didn't require a new transfer case.

Anyone know where to get the best price on a replacement actuator?

 

[100d ua]

I've been having the same problem where my CDL wont disengage.. ive been fortunate enough that it randomly turned off after hitting a bump or awkward curved driveway. I haven't troubleshooted it since but feel a new actuator is in order.

The removal process includes dropping the cross member and lowering the transfer case to access the part, correct?

 

[wildpaths]

The removal process includes dropping the cross member and lowering the transfer case to access the part, correct?

Here is exactly what I did.
0) Went underneath earlier today and gave it a wash with a spray nozzle to remove the grime and dirt.
1) Jacked the front up a bit and put it on jack stands. Wheels were still on the ground, but gave myself some extra room.
2) Removed the bash-guard for the Transfer Case (3 bolts at 12mm)
3) Put a jack under the cross-member, removed the 8 cross-member bolts (14mm), and dropped the assembly. Everyone said to would go down 2", but I got more like 1.5" or less, maybe due to my lift.
4) Removed the 4 bolts holding the actuator to the transfer case (12mm). Note that the front driver's side bolt is much longer than the other three.

For me it got difficult after that. There are two steel collars around the bolt holes on the rear passenger side and the front driver side, that serve as studs to align the actuator assembly correctly onto the transfer case. Given that I don't see them on the pictures of the new actuators, I assume these are supposed to stay attached to the transfer case. Unfortunately, due to age or corrosion, these stuck to the actuator assembly and I had to pry it off like opening a clam shell, because the front drives one would not release. I know it bent the actuator housing. It might have damaged the transfer case housing, but I can't see up there.

Good luck!

 

[wildpaths]

I'm going to be installing the new actuator early next week but need some advice on how to do it.

From my reading, people keep saying that it must be installed in the locked position. I am clear on how to get the actuator in the locked position - simply connect the electronic before installation and push the Center Differential (CD) Button into the locked position.

I am not so clear on how to make sure the CD itself is in the locked position. It is certainly "mostly" locked as the dash light is ON. It is "mostly" locked as the front wheels won't move independently.

But I can't tell if it is "fully" locked.

My old actuator was turning a little bit, but only about a 20% turn instead of the 70% turn it would do if fully rotating. This tells me there is a possibility that the actual CD locking assembly may not be in the 100% locked position.

I am also assuming that whatever hardware locks the CD has a range of positions, rather than just locked/unlocked.

Any thoughts?

 

[wildpaths]

Hah, no. I couldn't get mine to engage at all, so I assumed the actuator was broken and sourced a spare before tearing into it. Waste of money.

Turns out someone had been in there before, and just didn't put the motor back together properly. The actuator should be in the locked position on install, and the smaller loose gear (in your picture above) pushed as far south as it can go (also in the locked position). I jacked up the passenger side rear on mine, and could turn the tire with my foot while pushing on the gear until I felt it was locked.

Using @saucebox quote above, and this picture from another thread, I came up with a plan.

I will get under there, and see if I can move the shift fork shaft either direction. It might not move at all! Let's hope it does. Advice says I need to move it south (towards the rear). Then logic would also say that if I move it north (towards the front) it should unlock, which I can verify with the dash light, and by rotating the disk where the missing front drive shaft would attach.

Any warnings or gaps in this plan? I'm already missing one finger, so I like to check with the experts first.

 

[wildpaths]

Yeah... tried that. I can't rotate the actuator output gear to make the fork shaft move. Not by hand anyway. I can feel the geared track on the fork shaft through the 1" hole that the output gear rides in. So, maybe my best course it to assume it is fully locked and go for install as-is?

The only other thing I can think of it to jack a rear wheel off the ground and rotate to remove any binding and have a hope of maybe moving the fork shaft?

 

[wildpaths]

The only other thing I can think of it to jack a rear wheel off the ground and rotate to remove any binding and have a hope of maybe moving the fork shaft?

And that worked! Thanks @saucebox for this technique! I can now move it from locked to unlocked with my fingers. The CD Dash light responds appropriately, and the wheels lock.

I am super glad I did this so that I can be sure that it is is fully locked position when I install the actuator.

 

[wildpaths]

Update: Part arrived on Thursday. Install was successful and uneventful. Rig is back on the road. Did a successful dirt test last night.

While I was under the truck I noticed quite a bit of front end drive play. Imma diagnose that next.

 

[coolant]

Thanks for the thorough breakdown of your diagnosis and treatment, @wildpaths! I haven’t payed much attention to my transfer case, but I have experienced the CD needing a little coaxing to unlock. I’ll keep this thread for if I ever need to dig deeper and check out the actuator.