fixbroke
Well-Known Member
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TL;DR: rear axle locker light is flashing. Jeep dealer refuses to warranty it due to 4.88s. Problem seems to be locker sensor which is not available for purchase.
So here's the poop:
At around 2000 odo miles, I personally swapped some 4.88s into my new Gladiator Rubicon. It wasn't my first time tearing into diffs and I'm confident in the work. It took a bunch of shimming attempts, but I got a really nice wear pattern that I'm happy with. It ran hot, but I spoke with some experts who said that it was nothing to worry about and not abnormal. I've changed gear oil a few times and the teeth all look nice and happy inside without any excess sludge or shavings in the oil.
6000 miles later, I noticed on a long highway trip that my rear locker light was solidly on. I thought it was strange, but I turned the lockers off and kept going.
1000ish miles after that, the same thing happened on a highway trip while climbing a long hill. This time, however, the light wouldn't go out - it would only flash. It's now stuck this way. I've verified the locker works as normal (on when the light is solidly on, off when it's flashing).
I read a few stories of similar problems, with the warranty resolution being a whole new axle. With my 4.88s, I didn't relish the thought of having to re-gear a new axle but I brought it into my local dealer to see what could be done. As soon as they noticed the "aftermarket gears", they refused to do any warranty work on the axle. This was not entirely unexpected. No worries - I'm a mechatronics engineer, so I thought I'd open it up and do the troubleshooting myself.
The problem seems to be with the sensor that tells the Jeep when the locker is released. This guy, pictured below (pic shamelessly stolen from chevymitchell's excellent DIY 4.88 thread ):
When the locker is released (as pictured) a magnet slides into the sensor, telling the Jeep that the locker isn't engaged any more. I thought I'd found the smoking gun when the internal wire connector for the sensor turned out to be full of gear oil (the seal had evidently failed), but a thorough cleaning hasn't changed the function. That isn't to say that the oil hasn't gotten inside the sensor housing and ruined something, though.
I tried wiggling everything and I tried running magnets over the sensor, but the Jeep refuses to believe the locker is released.
There are basically two types of magnetic sensors: reed switches and hall effect sensors. This one is likely a hall effect sensor since reed switches aren't typically used in high-vibration environments like an axle housing. It has three pins on the sensor but only two of them are in use, so this tells me that it's a two-pin hall effect sensor that responds to magnetic fields with a change in current. To fully rule out the reed switch I checked resistance between the two active pins while running a magnet over the sensor and there was no change in resistance.
I checked the supply voltage at the sensor connector (6.5 volts), and bench tested the sensor at that voltage to see if I could induce any changes in current. No matter how large a magnet and no matter the polarity, no change to the current. I think the sensor is a dud. Perhaps it didn't like the prolonged heat, or perhaps it got gear oil inside. All I know is I can't get it to react to magnetic fields.
No problem, I'll just buy a replacement - right? Nope.
It turns out that the reason for the full-axle-replacement warranty work that others have received is because Jeep does not sell any axle parts (except for bearings and gears) for the Advantek 44. Bad sensor? Replace the whole axle, complete with housing. Seems pretty ridiculous for a $5 part! FCA part number 10031393, not available.
At this point I have few options. I could pester @JeepCares for help, though the answer there is almost always to see your dealer. I could pester Dana to see if they will sell me the part, but in my experience they refuse to deal with end-users. Lastly, I could bust open the sensor and make a last-ditch effort to fix it, but I'm guessing that any failures inside won't be fixable unless it's a simple broken solder joint.
Anyone have any thoughts or advice for me? (and no, putting a piece of electrical tape over the blinking locker light isn't an option! )
So here's the poop:
At around 2000 odo miles, I personally swapped some 4.88s into my new Gladiator Rubicon. It wasn't my first time tearing into diffs and I'm confident in the work. It took a bunch of shimming attempts, but I got a really nice wear pattern that I'm happy with. It ran hot, but I spoke with some experts who said that it was nothing to worry about and not abnormal. I've changed gear oil a few times and the teeth all look nice and happy inside without any excess sludge or shavings in the oil.
6000 miles later, I noticed on a long highway trip that my rear locker light was solidly on. I thought it was strange, but I turned the lockers off and kept going.
1000ish miles after that, the same thing happened on a highway trip while climbing a long hill. This time, however, the light wouldn't go out - it would only flash. It's now stuck this way. I've verified the locker works as normal (on when the light is solidly on, off when it's flashing).
I read a few stories of similar problems, with the warranty resolution being a whole new axle. With my 4.88s, I didn't relish the thought of having to re-gear a new axle but I brought it into my local dealer to see what could be done. As soon as they noticed the "aftermarket gears", they refused to do any warranty work on the axle. This was not entirely unexpected. No worries - I'm a mechatronics engineer, so I thought I'd open it up and do the troubleshooting myself.
The problem seems to be with the sensor that tells the Jeep when the locker is released. This guy, pictured below (pic shamelessly stolen from chevymitchell's excellent DIY 4.88 thread ):
When the locker is released (as pictured) a magnet slides into the sensor, telling the Jeep that the locker isn't engaged any more. I thought I'd found the smoking gun when the internal wire connector for the sensor turned out to be full of gear oil (the seal had evidently failed), but a thorough cleaning hasn't changed the function. That isn't to say that the oil hasn't gotten inside the sensor housing and ruined something, though.
I tried wiggling everything and I tried running magnets over the sensor, but the Jeep refuses to believe the locker is released.
There are basically two types of magnetic sensors: reed switches and hall effect sensors. This one is likely a hall effect sensor since reed switches aren't typically used in high-vibration environments like an axle housing. It has three pins on the sensor but only two of them are in use, so this tells me that it's a two-pin hall effect sensor that responds to magnetic fields with a change in current. To fully rule out the reed switch I checked resistance between the two active pins while running a magnet over the sensor and there was no change in resistance.
I checked the supply voltage at the sensor connector (6.5 volts), and bench tested the sensor at that voltage to see if I could induce any changes in current. No matter how large a magnet and no matter the polarity, no change to the current. I think the sensor is a dud. Perhaps it didn't like the prolonged heat, or perhaps it got gear oil inside. All I know is I can't get it to react to magnetic fields.
No problem, I'll just buy a replacement - right? Nope.
It turns out that the reason for the full-axle-replacement warranty work that others have received is because Jeep does not sell any axle parts (except for bearings and gears) for the Advantek 44. Bad sensor? Replace the whole axle, complete with housing. Seems pretty ridiculous for a $5 part! FCA part number 10031393, not available.
At this point I have few options. I could pester @JeepCares for help, though the answer there is almost always to see your dealer. I could pester Dana to see if they will sell me the part, but in my experience they refuse to deal with end-users. Lastly, I could bust open the sensor and make a last-ditch effort to fix it, but I'm guessing that any failures inside won't be fixable unless it's a simple broken solder joint.
Anyone have any thoughts or advice for me? (and no, putting a piece of electrical tape over the blinking locker light isn't an option! )
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