2004 Rubicon Rear Locker Troubleshooting (Air Pump / Pressure Okay)

Accelerometer

Accelerometer

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This one has me perplexed, I have a 2004 Rubicon with a non functioning rear locker. Not sure when it broke but it was most likely when I was on the Rubicon trail a few months ago. Here is what I've done so far to troubleshoot:
  • LSD seems to be functioning correctly as the Jeep still chirps around corners at slow speeds in the parking lot
  • When the rear locker is activated the air pump cycles and stops, the "REAR LOCKER" light in the dash stays solid
  • I pulled the rear diff cover off yesterday and found no metal debris in the oil
  • The axle has been put in the air and wheel rotated to confirm the axle is not in fact locked when the Jeep says it is
  • No audible sounds coming from the diff that would be indicative that something isn't right
  • When activating the rear locker you can see the locker collar slide over from the air pressure. So it appears that air pressure to the locker and bladder is good and it's actuating. A 5 second video of it can be seen here:
Any ideas? I didn't have time to pull the carrier out yesterday but hoping I'm missing something simple before I do that. Also, if it comes down to it any good sources for OEM lockers? I just checked the price for an Eaton and they are pretty up there.
 
Three things....

Does the pump shut off? You can power the locker pumps without engine noise with the key in the on position and tcase in 4low. Now you can listen to the pumps.

Lift a rear tire of the ground. Then activate the rear locker. Spin the raised tire by hand. Does the locker lock? Again, does the pump shut off?

The "chirps around corners at slow speeds in the parking lot" might be a clue. That is not normal. When it chirps, is there also a buck or a hesitation in the forward movement? This one is important as it suggests that the LSD is tearing apart and clogging the locker.
 
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jjvw said:
Three things....

Does the pump shut off? You can power the locker pumps without engine noise with the key in the on position and tcase in 4low. Now you can listen to the pumps.

Lift a rear tire of the ground. Then activate the rear locker. Spin the raised tire by hand. Does the locker lock? Again, does the pump shut off?

The "chirps around corners at slow speeds in the parking lot" might be a clue. That is not normal. When it chirps, is there also a buck or a hesitation in the forward movement? This one is important as it suggests that the LSD is tearing apart and clogging the locker.
Click to expand...

Yes the pump shuts off after probably 2 secs after it hits 5 psi. If you watch the video you can see its actually activating the locker collar. Ive tried the axle test you mentioned and the locker does not lock with a raised wheel off the ground. It free spins as if the diff was open.

Finally, the parking lot chirp may have been an over statment. You can hear the tires chirp but there is no bucking at all.
 
Accelerometer said:
....

Finally, the parking lot chirp may have been an over statment. You can hear the tires chirp but there is no bucking at all.
Click to expand...

The LSD should not make the tires chirp at all. Mine never did for tens of thousands of miles, except for when the LSD was tearing apart. The pieces of the LSD would also clog the locker.

This is why mine now has ARB lockers front and rear.
 
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If you kept your locker unlocked most of the time on the Rubicon trail and mostly relied on just its LSD odds are very good the locker is broken. The Rubicon's rear locker is notorious for breaking if it isn't kept locked on sections of trails that cause its tires to spin and then catch. I keep my Rubicon's rear locker locked once I am in 4Lo and only unlock it once I shift out of 4Lo. If it's broken a front Rubicon locker will work just as well in the rear and not have as big of a likelihood of breaking again.
 
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Jerry Bransford said:
If you kept your locker unlocked most of the time on the Rubicon trail and mostly relied on just its LSD odds are very good the locker is broken. The Rubicon's rear locker is notorious for breaking if it isn't kept locked on sections of trails that cause its tires to spin and then catch. I keep my Rubicon's rear locker locked once I am in 4Lo and only unlock it once I shift out of 4Lo.
Click to expand...

Other way around. It is the LSD that breaks apart when it gets relied upon. It is the Rubicon LSD that is notorious for breaking if the locker isn't locked. Then the chunks of LSD clog the locker and stop it from locking. But the locker is not really broken.
 
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jjvw said:
Other way around. It is the LSD that breaks apart when it gets relied upon. It is the Rubicon LSD that is notorious for breaking if the locker isn't locked. Then the chunks of LSD clog the locker and stop it from locking. But the locker is not really broken.
Click to expand...

I took is as the LSD catches, breaks, and the "Locker" = "Locking Differential Overall" no longer works. You're being more specific, the locking mechanism isn't broken, the LSD is broken and the pieces are clogging the locking mechanism.

Functional terms, the LSD jacks up, the "locker no workie" ha.

I'm assuming the front locker would work better....because it doesn't have the LSD? So the LSD won't break, and thus not run the risk of then causing "The Locker not working at all" because the LSD blew up?
 
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cpwolf said:
I took is as the LSD catches, breaks, and the "Locker" = "Locking Differential Overall" no longer works. You're being more specific, the locking mechanism isn't broken, the LSD is broken and the pieces are clogging the locking mechanism.

Functional terms, the LSD jacks up, the "locker no workie" ha.

....
Click to expand...

Your argument is that Jerry is being slightly more specific than saying the Jeep quit working. I agree that he is, specifically where the meanings of words don't matter.

cpwolf said:
...
I'm assuming the front locker would work better....because it doesn't have the LSD? So the LSD won't break, and thus not run the risk of then causing "The Locker not working at all" because the LSD blew up?
Click to expand...

The problem is that the Rubicon front locker is still a smaller locker compared to other options. It is undersized for the larger demands of a rear axle. But at least it doesn't have a gear driven LSD to break apart and clog the locker.
 
jjvw said:
The LSD should not make the tires chirp at all. Mine never did for tens of thousands of miles, except for when the LSD was tearing apart. The pieces of the LSD would also clog the locker.

This is why mine now has ARB lockers front and rear.
Click to expand...

tworley said:
X2. Chirping (and in my case, bucking) is not normal. Your LSD isn't functioning correctly.

Similarly, I have an ARB in the rear
Click to expand...

Super helpful guys, I never owned a vehicle with a mechanical LSD/locker hybrid before so I was just assuming this was normal behavior.
 
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Jerry Bransford said:
If you kept your locker unlocked most of the time on the Rubicon trail and mostly relied on just its LSD odds are very good the locker is broken. The Rubicon's rear locker is notorious for breaking if it isn't kept locked on sections of trails that cause its tires to spin and then catch. I keep my Rubicon's rear locker locked once I am in 4Lo and only unlock it once I shift out of 4Lo. If it's broken a front Rubicon locker will work just as well in the rear and not have as big of a likelihood of breaking again.
Click to expand...

My rear locker was "locked" for the entire trail because I knew about the fragile LSD. However, I am starting to have think that this locker was broken the day I bought the Jeep almost a year ago. The reason I never noticed it was because I was assuming all things were good with the dashboard confirmation light staying solid. The front locker has been carrying me for the last 12 months.

Is the front locker a direct drop in?
 
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jjvw said:
Other way around. It is the LSD that breaks apart when it gets relied upon. It is the Rubicon LSD that is notorious for breaking if the locker isn't locked. Then the chunks of LSD clog the locker and stop it from locking. But the locker is not really broken.
Click to expand...

So in theory I could pull the carrier and remove the broken LSD bits and go my way? Assuming you can run like an open diff with a broken and self removed LSD? Sorry for the dumb question Ive never tinkered around with a mechanical LSD. I have one in my BMW M3 but I havent had to open it up yet. I've worked on plenty of lockers though.
 
Accelerometer said:
Super helpful guys, I never owned a vehicle with a mechanical LSD before so I was just assuming this was normal behavior.
Click to expand...

The fundamental problem with the Rubicon rear combo LSD/locker is that both units are reduced in size in order to cram everything into one space. The other common gear driven TruTrack LSD isn't known to break apart in part because it's components are larger because it is a just a dedicated limited slip.
 
Accelerometer said:
So in theory I could pull the carrier and remove the broken LSD bits and go my way? Assuming you can run like an open diff with a broken and self removed LSD? Sorry for the dumb question Ive never tinkered around with a mechanical LSD. I have one in my BMW M3 but I havent had to open it up yet. I've worked on plenty of lockers though.
Click to expand...

You can do that. You need to replace the broken LSD bits for the differential to function. But then you are trusting both your source parts the are used with an unknown history and your workmanship. I could have done that. I had the parts to do it. But I still chose to go with ARB in the rear. Later, I also changed the front to ARB due to my lack of trust in the factory lockers.
 
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Accelerometer said:
Yes the pump shuts off after probably 2 secs after it hits 5 psi. If you watch the video you can see its actually activating the locker collar. Ive tried the axle test you mentioned and the locker does not lock with a raised wheel off the ground. It free spins as if the diff was open.
Click to expand...

Broken axle?
 
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