Does the factory rear diff work?

Watamu LC

New Member
I am in kenya
Feb 20, 2015
24
2
8
Kenya
Dear all,

I have recently managed to find a "new" ECU for my KZJ78.
The new computer box solved the niggle where the "O/D OFF" light would blink continuously when I disengaged the overdrive.
The overdrive always worked perfectly well, so always found this to be a little odd.

I had hoped that the new ECU would also sort out the flashing light of the factory rear diff lock.
When I lock the hubs (electronic), then shift to low range gearing and engage the diff lock (push and turn knob below the steering wheel), the red indicator light starts flashing on the dash.

Does this mean it is working or does it mean there is a problem?
Blinking = bad, I think? :think:
How can I test whether the diff is working?

Thanks for the help!
 

StarCruiser

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Sounds like a sticking diff lock actuator. Have you tried driving it a little bit on a slippery (well off road not Tarmac) surface? It will either click on and go solidly on or stay blinking. If it stays, it may be worth inspecting the actuator. They get a bit sticky if left unused for a while, sometimes corroded badly if water gets in. I'm guessing you don't have a road salt problem so it's probably not badly corroded.
 

Watamu LC

New Member
I am in kenya
Feb 20, 2015
24
2
8
Kenya
Sounds like a sticking diff lock actuator. Have you tried driving it a little bit on a slippery (well off road not Tarmac) surface? It will either click on and go solidly on or stay blinking. If it stays, it may be worth inspecting the actuator. They get a bit sticky if left unused for a while, sometimes corroded badly if water gets in. I'm guessing you don't have a road salt problem so it's probably not badly corroded.
I have tried using it a number of times on gravel/sandy roads but no change to the blinking red LED on the dash.
The previous owner used the car to drive in town, don't think the diff lock has been used in a while.
What is the best way of getting it unstuck?
 

clivehorridge

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I am in romania
May 23, 2012
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On my 80, in the 11 years I've owned it, the rear locker indicator light has never gone solid, and it gets used at least once a week.

It works just fine, engaging and disengaging, but it never shows solid.

I've always put it down to some electrickery, so to save any accidental loss of that precious smoke, I haven't played with any wires.
 
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StarCruiser

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What is the best way of getting it unstuck?
It's worth checking under the truck the state of the actuator and wiring. If nothing seems to be amiss I would remove it and open it up on the bench, inspect it and work the parts manually to see that they operate correctly. I would then lubricate it, reassemble it and connect it back onto the wiring on the truck, but not bolt it on yet and operate it to see if the light goes out. If all was well I would then refit it to the diff.

You could try doing a search on here for any info on diff lock actuators. I don't own one but I've read about the 80 ones on here getting a bit sticky.
 
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TL75

Active Member
I am in pakistan
Jun 7, 2017
52
55
18
Dear all,

I have recently managed to find a "new" ECU for my KZJ78.
The new computer box solved the niggle where the "O/D OFF" light would blink continuously when I disengaged the overdrive.
The overdrive always worked perfectly well, so always found this to be a little odd.

I had hoped that the new ECU would also sort out the flashing light of the factory rear diff lock.
When I lock the hubs (electronic), then shift to low range gearing and engage the diff lock (push and turn knob below the steering wheel), the red indicator light starts flashing on the dash.

Does this mean it is working or does it mean there is a problem?
Blinking = bad, I think? :think:
How can I test whether the diff is working?

Thanks for the help!
Hi,
I own the same vehicle as you.
The light usually blinks when the diffs are being engaged and once they lock the light should turn solid. Basically the blinking light indicates the transition from unlocked to lock .
First off I suggest you check your rear diffs by simply jacking up your vehicle from the rare . both wheels if possible. Put your Car in neutral . Engage the rear diff locks. Then try and rotate the wheels by hand. If one wheel is jacked up and the diffs are working the wheel will not rotate . If both wheels are jacked up then try spinning the wheels in opposite direction after the diffs are engaged.

The Rear diff lockers on the KZJ78 are electronic. so if they are not working then it could be a multiple problems but nothing complicated.
1. your actuator could be stuck
2. your motor is not working ( for various reasons)
3. it could be as simple as your electronic motor needing a service or adjustment.

The light is actually turned on or off by a little switch in the diff so if your diffs are locking and the light keeps blinking it could be a faulty switch. if the diffs are not locking and the light is blinking then the light is spot on.
Hope this helps.
Is your KZJ78 auto or manual.

Other ways of telling if your diffs are locked.
1. the vehicle will be more difficult to turn as such or rather lets put it this way your vehicle would prefer straight driving instead of turn so when you turn and let the steering wheel go the wheel will return to its centered position quicker than usual.
2. the inner tire will travel less than the outer tire hence you should be able to hear some sort noise on the gravel etc from the outer tire cause its literally hoping . Do not engage diffs on hard surfaces.

Good luck
 

clivehorridge

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Sure, if the rear diff is locked, and you do a tight full-lock turn slowly on grass or gravel, it will be obvious, the (usually inner) rear wheel will skid and skip because it's trying to rotate at the same rate as the outer wheel, but it's traveling a shorter arc.

I would simply pull the connectors from the rear actuator first, give them a good clean up and re-try.

If that doesn't work, then as StarCruiser said, pull the actuator and clean it up inside, on the bench, and test it with the truck wiring, but off the truck.
 
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Ben

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I am in australia
Oct 13, 2010
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Melbourne, Australia
I have the exact same issue with my LJ78, the light has always flashed since I bought the vehicle but I havent had chance to investigate it properly yet, but I will over the next few weeks. :icon-biggrin:

There is a little box that controls it that should be mounted at the base of the A pillar, in the front passenger foot well (on right hand drive 70's anyway).

As far as I can tell thats the computer and when you turn the switch to activate the locker it checks with the sensor on the transferbox to make sure your in low range, then sends power to the actuator mounted on the diff. :icon-ugeek:

If I remember when I get home I will scan the pages in the FSM that covers trouble shooting for the rear diff lock and post the pics on this thread for you. ;)

If/when you do manage to fix yours please tell us what was wrong and how you fixed it. :icon-biggrin:
 
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Watamu LC

New Member
I am in kenya
Feb 20, 2015
24
2
8
Kenya
Dear all,

many thanks for the replies and the tips on how to check whether the diff lock is working.
I have not had a chance to play around with it but will do so soon & get back to you my findings. :)

Happy trucking!
 
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