CDL stuck engaged? Actuator doesn't function/make sound, but axle lockers work in high range (1 Viewer)

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Sep 19, 2020
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Redwood City, California
Howdy folks,

I picked up my first 80 last week (traded my 40 crawler for it) and drove it about 100 miles up until this point. I had time today so I was messing with my lockers/ tcase and I couldn't hear or feel the CDL engaging or disengaging. I went home and engaged the both front and rear ockers in high range, which I thought was funny because they require the center locker to be engaged in order to work. First I jacked up one wheel and tried to turn it (without the axle locker engaged and wasn't able to turn the wheel-but maybe I wasn't trying hard enough, not sure how much force is needed to overtake the viscous coupler)
Then I put the truck on jack stands and, with all the wheels in the air, I turned 1 rear wheel and 1 front spun. This would be normal with a viscous coupler, correct?
The truck drives normally, no real scrubbing while I turn, no chirping either. So it's hard to determine if the CDL in on or off.

I am a little worried about trans wind up but it seems fine. I won't drive it anywhere far in the near future until I have this figured out.
Onto the diagnosis/description:
-No ABS light/ No CDL dash indicator light
-P/O did not install the CDL switch (I'll check if it has the 7 pin mod later tonight)
-30a fuse in the cab is good
-buying a multimeter tonight to check the CDL control relay by the left foot kick panel
-no CDL actuator noise going between high-N-low or low-N-high but no ABS or CDL dash indicator light is present (but the ABS light does work, as I see it light up during startup but turns off while I drive)
-electrical connectors at actuator on tcase seem intact but will test with multimeter

I've read a few threads so far, and from what I'm reading I'm assuming it could be:
1. a bad CDL control relay
2. broken actuator
3. broken viscous coupler
4. funky wiring allowing axle lockers to engage without CDL engaging (or disengaging)

Sorry for posting another "CDL issue" but from what I read I couldn't find the same symptoms that someone else has fixed. But I'll keep looking.
If any of these symptoms ring a bell and someone has the answer, let me know! If it's not the relay I'll most likely drop the tcase tomorrow and take off the actuator.
Cheers,

Nikolai
 
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Joined
Sep 19, 2020
Messages
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Redwood City, California
Been talking with a local cruiser guy and it got me thinking: is it possible to bypass the center locker in order to engage the front and rear lockers in high range/ low range without the center diff locking? Anyone know the wiring circuits that would enable someone to do this? Maybe I should track down some funky wiring first... this has me scratching my head
 
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On my cruiser the magnets failed in the center differential lock actuator. They became dethatched and kept the actuator from operating. Had to glue them into position.
 

Squash

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Check the sensor wiring forward of the cdl motor. You can complete the cdl circuit easily from this location.
Actually remove the sensor and your baby finger should be able to feel the plunger, or use your phone camera for a visual.
 
Joined
Sep 19, 2020
Messages
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Location
Redwood City, California
Check the sensor wiring forward of the cdl motor. You can complete the cdl circuit easily from this location.
Actually remove the sensor and your baby finger should be able to feel the plunger, or use your phone camera for a visual.
Thanks for the reply. Are you talking about the CDL sensor switch on top of the actuator, the one that is easily accessible? I'll try the paperclip test this morning and see if I can complete the circuit.
 
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Bay Area, Ca.
Been talking with a local cruiser guy and it got me thinking: is it possible to bypass the center locker in order to engage the front and rear lockers in high range/ low range without the center diff locking? Anyone know the wiring circuits that would enable someone to do this? Maybe I should track down some funky wiring first... this has me scratching my head
Yes, it's possible. You may be on the right track.

 
Joined
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Redwood City, California
I'm curious as to why my axle lockers will engage in both high range and low range, AFAIK the only possible way to do this would be the pin 15 mod, and from what I've read that would include disconnecting the YELLOW wire with BLACK tracer ('93-'94 cars) from the Diff lock ECU (named tranny ECU) on the passengers right kick panel. I'll check for that mod. Besides bypassing the CDL with the pin 15 mod, what else could cause the axle diff lockers to engage without the CDL locked?
 
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Yes, it's possible. You may be on the right track.

I've heard of you, Landcrshr sir. Thanks for the reply.
 
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Ok, now I'm really perplexed. I checked the CDL relay (drivers left foot kick panel behind silver box) and 7 pin mod was NOT done (everything is in tact), then I checked the axle diff lock relay (pass right foot kick panel) and 15 pin was NOT done, it is also in tact.
I checked the voltage of the CDL sensor/switch connector on top of the T-Case and it was giving me 11.5v in both high and low range. I then tried the paper clip trick to see if the CDL dash light would work or not. Nothing. No light or any change.

So how can the lockers be engaging in both high and low range? Is the center diff really stuck engaged with no indication that it is engaged? i.e. no CDL dash indicator, no ABS light (ABS light works)
Or is the CDL NOT engaged, yet somehow the axle lockers work without the CDL, without the 15 pin mod? I'm not feeling any scrubbing or abnormal driving conditions so it's hard to say whether it's on or off though. I did the one wheel lift test and was unable to turn it, but again I'm not sure how much force is required to overcome the viscous coupling.
Anyone else have any ideas??
 
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Messages
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Redwood City, California
Another point, both the ABS and CDL indicator lights on the dash work, just took apart the interior, grabbed the unused CDL switch harness because I just ordered the CDL switch from Slee.
I did try the hazard trick too, hooked up the unused CDL harness to the hazard switch, and hit the button multiple times in high range, low range, park, neutral, drive, etc, etc, etc....
nothing at all.
I friend of mine mentioned to check the ground wires on the tcase so I'll check that next.
 
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I'm curious as to why my axle lockers will engage in both high range and low range, AFAIK the only possible way to do this would be the pin 15 mod, and from what I've read that would include disconnecting the YELLOW wire with BLACK tracer ('93-'94 cars) from the Diff lock ECU (named tranny ECU) on the passengers right kick panel. I'll check for that mod. Besides bypassing the CDL with the pin 15 mod, what else could cause the axle diff lockers to engage without the CDL locked?
To clarify, the only thing needed to enable diff locks without the CDL engaged is to ground pin 15 of the diff lock ECU. Pin 15 remains connected to the diff lock ECU, but runs to a ground lug on the body.
In an unmolested configuration, when the CDL locks, it grounds pin 15.
 
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To clarify, the only thing needed to enable diff locks without the CDL engaged is to ground pin 15 of the diff lock ECU. Pin 15 remains connected to the diff lock ECU, but runs to a ground lug on the body.
In an unmolested configuration, when the CDL locks, it grounds pin 15.
Understood. From what I can tell it looks like there’s no modification to that pin/ wire. I don’t see any extra ground coming from that wire. Could it be my CDL is locked then? All arrows point towards -> yes
I checked the dash bulbs and they are working, but they don’t flash or blink when shifting between high/ low.
 

Squash

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You can lower the t-case by removing the cross member bolts.
Swap the factory bolts for 4 to 6 inch bolts to give you room to work. Jack stands or wood cribbing also work.
Use good 6pt sockets.
Unplug wiring at rear of t-case.
You can try a 9volt battery at the connection should be the thickest wires. Try one way, swap leads and try the other way. At this point the front sensor can be removed and physically check if plunger has moved. I have used 12 volts but do not hold power...just a quick touch!
If you decide to remove the actuator make sure you reinstall in the locked mode.
At this point I would take the unit apart, regrease, check magnets and stick my hand into the t-case to feel the lock/unlock mechanism. Good time to reinstall sensor to see if dash lights up.
 
Joined
Sep 19, 2020
Messages
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Location
Redwood City, California
You can lower the t-case by removing the cross member bolts.
Swap the factory bolts for 4 to 6 inch bolts to give you room to work. Jack stands or wood cribbing also work.
Use good 6pt sockets.
Unplug wiring at rear of t-case.
You can try a 9volt battery at the connection should be the thickest wires. Try one way, swap leads and try the other way. At this point the front sensor can be removed and physically check if plunger has moved. I have used 12 volts but do not hold power...just a quick touch!
If you decide to remove the actuator make sure you reinstall in the locked mode.
At this point I would take the unit apart, regrease, check magnets and stick my hand into the t-case to feel the lock/unlock mechanism. Good time to reinstall sensor to see if dash lights up.
Thanks for the info.
I'll finish my electrical hunt in the cabin before I drop the case today, I'm about to check the CDL relay, I think its also near the driver's left foot kick panel. Hopefully that's my issue, but I'll also check the CDL switch at the case/actuator side with a 9v battery and see if it moves.
Is it strange that I'm getting 11.5v power to that switch/sensor in both high and low range, yet nothing occurs?
 
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If the CDL was locked you would know it when you drive. That is UNLESS maybe you had a broken axle or stripped drive flanges. If there is a breakage in the driveline, the PO may have done the work to permanently lock the CDL and disable the status lights. Just a thought.
 
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If the CDL was locked you would know it when you drive. That is UNLESS maybe you had a broken axle or stripped drive flanges. If there is a breakage in the driveline, the PO may have done the work to permanently lock the CDL and disable the status lights. Just a thought.
Not a bad idea, I'll look for some clues
 
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Messages
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Update:
The paper clip trick worked, on the second try. First time it didn’t work this morning (maybe I didn’t have the connection correct) but now my CDL light and ABS light turn on. So that must leave the problem in the transfer case. I tried to get a 9v battery in the top CDL switch connector with no avail.
Would this be a sign of a failed actuator? I guess the next step would be taking the actuator off and inspecting it.
 

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