Rear diff lock- how do I know if it's locked??

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How do I know if my rear diff is locked?

I have been working on my CDL and diffs. I have another tread discussing that process but it seems to me that this is a different issue that should have its own thread. I got the CDL working and now on to the lockers. I did the gravel figure 8s again, but with front AND rear locked (on the dial). The front immediately locked up- the light went solid and I could tell that the front was definitely locked. The rear just kept blinking. So, I thought the front would not lock unless the rear was locked?? How does the front know when the rear is locked or not?

I tried jacking up the rear and turning one wheel to get the rear to lock, but it would barely turn at all. Is that probably because it WAS locked, but just not indicating locked on the dash?

Also, when I originally jumpered the CDL, both front and rear would show locked right away in my driveway.. not sure what that means if anything.

So, how do I verify the rear is locked or unlocked and how does the rear diff indicate it is locked so the dash light goes solid?
 
The front locker has more cogs, so it will usually lock quicker than the rear.

The rear locker has less cogs, so it's stronger than the front, but usually requires more difference in rotation left to right in order to engage.

For testing, your best bet is to put it on jack stands (all 4 wheels up)

Engage the lockers one at a time (Center, Rear, then front)

Check by turning the wheels by hand.
 
When I was testing driving my car, I was in the parking lot on a busy street, but I can still hear it and feel it jerk a bit while driving very slowly. I confirmed it was locked by turning, the inside wheel will start screeching. The front is easy to tell, turning will be a lot stiffer.
 
But isn't the rear supposed to be locked before the front will lock? Is it possible that the rear is locked but indicating unlocked, thereby allowing the front to lock??
 
But isn't the rear supposed to be locked before the front will lock? Is it possible that the rear is locked but indicating unlocked, thereby allowing the front to lock??

What makes you think the front won't lock unless the rear is locked?

cheers,
george.
 
But isn't the rear supposed to be locked before the front will lock? Is it possible that the rear is locked but indicating unlocked, thereby allowing the front to lock??

No, each locker will lock when it's convenient

If I crank the knob all the way, 9 times out of 10 the front will lock before the rear :meh:
 
Not sure why I thought the rear had to lock first. When Injacked up one rear wheel and tried to turn it, it would turn the driveshaft. Why would that be if it wasn't locked?

Thanks for the replies.
 
How do I know if my rear diff is locked?
.
So, how do I verify the rear is locked or unlocked and how does the rear diff indicate it is locked so the dash light goes solid?

Just like the 4L and the CDL indicator switches on the transfer case, the front and rear diffs have identical switches. Jumper the harness to test the dash lights. If that works pull the switches and spray them on the end with WD40 and repeatedly (50 times) exercise the switches by hand. Test with a meter for zero resistance when pushed in. Keep repeating the process until they work properly. Put them in and then go test the locker.

george_tlc has a write up on his website on how to use a 9V battery to restore them to working condition.
http://www.george4wd.taskled.com

Pick the "Center Diff Lock Sensor/Switch" link on that page.
 
Not sure why I thought the rear had to lock first. When Injacked up one rear wheel and tried to turn it, it would turn the driveshaft. Why would that be if it wasn't locked?

Thanks for the replies.

You do understand how an open diff works versus a locked diff, yes?

cheers,
george.
 
George, well I thought I did, but not so sure any longer. Are you saying that my rear diff must have been locked? Please elaborate.
 
If your only jacking up one rear wheel and the other is on the ground then of course it won't turn. It will try to turn the driveshaft. At least jack up both rear tires. With both in the air go and turn one by hand. The other side should turn the opposite way if it's unlocked. Engage the locker then spin the tire again and after a few degrees of rotating it should lock up and the it should stop turning.

Also the front can lock before the rear BUT with how to dial works you always engage the rear before the front.

Hopefully all that is right ..
 
All right guys. I will jack up both wheels and try it. Also, it is possible that it's locking but just not indicating locked, correct? Thanks, Dan.
 
All right guys. I will jack up both wheels and try it. Also, it is possible that it's locking but just not indicating locked, correct? Thanks, Dan.

https://forum.ih8mud.com/showpost.php?p=1012338&postcount=4

specifically:

http://www.lcool.org/technical/diffs/diffs.html

and for the rear if you have a problem:

https://forum.ih8mud.com/80-series-tech/570087-repairing-differential-e-lockers.html

Do note:

1) for the f/r lockers to work, the CDL must show that it is locked on the dash (solid light)

2) with the f/r locker switch set to locked on the rear both the ds and ps rear wheels will rotate together, if they don't then the rear isn't locked or an axle has snapped :)

3) front and/or rear locker indicating locked on the respective dash light is based ONLY on the sensor/switch in the locker mechanism (just like the CDL).

4) with the CDL actually locked, vehicle stationary and the front wheels on a high traction surface, the rear drive shaft can't rotate beyond a small amount of backlash. If it does rotate more than that, then the CDL is not locked.

5) We really need to have all the CDL and F/R locker stuff/interaction etc in ONE thread....

cheers,
george.
 
The switch that indicates if the locker is locked or not is pretty easy to pull. It looks like a large bolt (24mm I think) with two wire come out of it. I used a Channel lock pliers and was able to get it loose. You may need the correct size open end if it is tight. Once out have someone sit in the cab and watch the dash to see if it stops blinking. Then crawl under the truck and push the indicator switch manually. Make sure your CDL is locked though. If it does not stop blinking the switch may be bad. I had to pull my switch from my CDL and lube it and work it back and forth before it worked properly. I priced this switch out through Akella and I think it was around $45.

My rear locker makes a nice click when it engages and disengages. Your accuator may not be working also. That can be pulled and you can watch the gear turn while someone turns the switch in the cab. There are many threads on how to rebuild if it is not working.
 
I have already replaced two of those switches. I used the Beck Arnley ones for about $18. Probably easiest to just get another on the way. I will try jacking it up and testing it correctly this weekend and report back. I can easily hear the electronic movement noise coming from the diff when I engage the locker. If that is moving, it it likely that it is locking but just not indicating locked? Thanks much, Dan.
 
Hmm, I guess would have to agree with the other guys then. Jack it up lock it in like you normally do and see if your wheels spin together not opposite of each other. If it is locked in then you may have a wiring issue or dash light issue. That is beyond me but I know there are guys on here that have tackled that. Good Luck
 
I just drove my FZJ80 for 10 minutes or so with the CDL switch depressed...and magically my ABS light and the center diff lock switch illuminated! now when I try my factory lockers, the front diff lock dash light illuminates, but the rear diff lock light keeps blinking! any ideas?
 
I just drove my FZJ80 for 10 minutes or so with the CDL switch depressed...and magically my ABS light and the center diff lock switch illuminated! now when I try my factory lockers, the front diff lock dash light illuminates, but the rear diff lock light keeps blinking! any ideas?


The rear locker has less teeth than the front and usually requires a larger difference in wheel turns from side to side in order to engage :meh:

Try engaging the rear only and do some figure 8 turns on a slippery surface (mud, gravel, snow, etc.)

Once the rear is engaged, disengage and re-engage a few times to make sure it's working properly.
 

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