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Discussion Starter · #1 ·
2014 Automatic. Stock 4:1 transfer case with front and rear Tom Wood drive shafts with 1310 yokes.

This started about a month ago. Shortly after a big 4LO wheel speed hill climb (probably a coincidence), a few minutes later I was stopped and hit the gas in drive and it just revved for a few seconds then lurched into gear and went. A few seconds later I lost power again and it sat a few seconds then went. I had never once experienced this in drive (only time I've experienced similar symptoms is when switching from drive to reverse in 4LO, but that's a well documented and known software bug in the JK - but it feels exactly the same).

Next wheeling trip it just happened once, brief loss of power mid-way through a brief use of throttle.

Next two days on the trail, never had any problems all day.

Then today I had major issues. Dozens of times I'd be driving along and just suddenly lose all connection to the axles (both front and rear). Revs for a few seconds then gets going again with a lurch but no grinding gear noises. At one point it was oscillating between being in and out of gear twice a second for about 5 seconds. The computer at least sometimes knows that it's falling out of gear because the lockers will disengage and the 4WD light turns off (same things happen if you switch the case into neutral). There's no way to reproduce this issue and it happens in all conditions. Low-throttle "high" speed (10-15MPH in 4lo of course), or down hill engine braking (terrifying to lose that on a steep hill, almost wrecked the Jeep), or big hill climbs, or starting from a stop. But I can also do all those activities all day and have it never happen some days.

At no point does the lever actually move. It always stays in 4LO. Yes I know how to shift into 4LO and the lever shifts in exactly the same as it always has. I can feel the gears meshing if I'm moving very slow and go into gear and it feels good and normal. Pushing the lever towards neutral while engaged doesn't make it fall out so it doesn't seem likely to be a loose or poorly adjusted shift lever.


Could this actually just be an electrical issue? At one point today I was stopped after the issue happened and the 4WD light was just flickering for a few seconds. Does the transmission go out of gear if it thinks the transfer case is in neutral? Since there's no gear noise when it re-engages, I'm skeptical that the transfer case is actually going out of gear at all. It feels like the automatic transmission going into neutral and coming back. But this is my daily driver and this never happens in 2HI (I don't drive in 4HI enough to even know but I've never experienced it - I'm quite confident this is a 4LO issue).


Checked out the transfer case today and noticed that the front output shaft is leaking and the case is all oily in the front. I'll need to fix that, but I pulled the fill plug and oil poured out (factory over-fill) and was a good clean red color, so I seriously doubt the leaking output shaft is at all related since there's plenty of oil in there.


Anyone experience something like this? Any ideas? I don't have much knowledge in drive train diagnostics so not sure quite where to approach this. It can't be reproduced so I can't really take it into a shop and get help even if I wanted to (and no chance on dealer drive train warranty without reproducing it). Never seen this sort of issue discussed on forums.
 

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Discussion Starter · #3 ·
I'm thinking it is the transfer case shift sensor. I just unplugged that and it destroys the vehicle. You can't even drive in 2WD. All gears, all transfer case settings, it just revs in neutral and makes awful clunking noises when shifting R/N/D.

It's always fun finding relatively pointless sensors that brick the JK platform.

Since I saw the 4WD light flickering while stopped, I guess my first diagnostic step will be replacing that part unless anyone has better ideas! Hope it's the sensor and not the wiring harness.
 

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Discussion Starter · #5 ·
Put about 2.5 days of wheeling in 4LO on it so far and have not once had it drop out since replacing the sensor. Looks like if anyone has this problem, the solution is replacing that transfer case sensor. I don't think it's a common failure though as I've never heard of this one before.

Got the part for $40 on ebay and it takes <5 minutes to replace (it just unscrews and a new one goes in, the hardest part is figuring out how to get your wrench into the very confined space above the drive shaft which I did not have to remove).
 

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Discussion Starter · #7 ·
The part is 5083138AA. If you look right up above the shift arm and front output shaft of the transfer case, you'll see that thing on top with a wire coming out. Unplug it, unscrew it (used a big adjustable crescent wrench), move the o-ring over to the new one (or ideally also order the o-ring if you can find the part number), and screw the new new one in and connect wire.

I was able to do it without removing any parts from the Jeep, but no guarantees as I'm running an aftermarket drive shaft and my crossmember is custom and re-located. 95% sure you could do it on OEM too without removing any parts though.
 

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Discussion Starter · #9 ·
No luck, it's back at it again. Transmission fell out of gear three times on the trail today when in 4Lo. Still never had it happen outside 4Lo. Been out many days since the repair and never had it happen, but now it's back.

Unless my new sensor already went bad, I guess it's something else. If it is sensor related, maybe there's some internal alignment problem where it's not pressing the multi-position switch to the right level.

Anyone know of any scan tools that can log absolutely everything continuously that would key me in on why the computer decides it needs to put the transmission into neutral?


I'm about ready to just put in an LS between this, my new P0520 oil pressure sensor issue, and misfire codes. Not quite in my budget plans right now though so I'll probably try to keep this drive train going for a while.
 

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I would only suggest this if you are serious about going to LS but both HP Tuners and EFI Live would be valuable for monitoring everything currently as well as being able to support any tuning needs you’ll have with the swap.

Both are a little spendy and I would only purchase credits for Chevy. Even with Chevy credits either will allow you to monitor Chrysler side.
 

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Discussion Starter · #11 ·
I would only suggest this if you are serious about going to LS but both HP Tuners and EFI Live would be valuable for monitoring everything currently as well as being able to support any tuning needs you’ll have with the swap.
I'm not serious about doing an LS swap. I sort of want to and "could" afford it but it'd be a seriously poor financial decision compared to other life priorities. Plus this year I really just wanted a Jeep that worked and I could drive.

Really, I want a scan tool for the 3.6L that I can drive on trails for days on end to reproduce the problem perhaps one time (I hate problems like this) and then get home, plug it into a computer, and look through data logs of the transmission state machine and all its sensor states to figure out what is logically driving it to go into neutral.


I'll look into those tuners you suggested. I honestly don't know how else I could debug this, a problem which is presumably driven by software and happens perhaps a few times a month. Without data logging, it seems it'd be hopeless but if anyone has other ideas I'm all ears!
 

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youve verified the ATF+4 leve”s in both your tranny and the xfer case are within spec ? If so, this sure sounds like an electronic bug of some sort. Do you run a tool such as TorquePro or have a PID scan option for displaying trouble codes in your tuner?
This has to be throwing some manner of code that may be useful. I so feel as tho’ I’ve read someplace about something similar occurring when the Auto Tran couldn’t pickup fluid at extreme angles or was low on fluid bu5 I can’t find the info for you ( yet).

:jeep2:
 

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Discussion Starter · #13 ·
youve verified the ATF+4 leve”s in both your tranny and the xfer case are within spec ? If so, this sure sounds like an electronic bug of some sort. Do you run a tool such as TorquePro or have a PID scan option for displaying trouble codes in your tuner?
This has to be throwing some manner of code that may be useful. I so feel as tho’ I’ve read someplace about something similar occurring when the Auto Tran couldn’t pickup fluid at extreme angles or was low on fluid bu5 I can’t find the info for you ( yet).

Both fluids are at the right level.

I just have a superchips flashcal that can read engine codes such as P0520 (I think called MILs but not sure). I've never gotten a code from this.

Are PID codes different and more thorough?

This happens on level ground sometimes so I seriously doubt it's pickup related.
 

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Think of the vehicle’s OBD system as one large message bus with a message queue of sorts.

In order to subscribe to a particular message series on that bus you need to know the message’s identifier or PID. Once you know the PID for a particular message series you can then grab a snapshot or stream the real time messages in that series. Keep in mind some values are raw or real sensor data and some are calculated data.

There are minimum messages series that are required to be available on all OBD controlled vehicles, as mandated by fed reg, but there are essentially no limits on manufacturer specific message series and most all are extensive. This is why most basic scanners are limited in functionality and only capable of reading mandated message series. The scanner must have a catalog of manufacturer specific PIDs in order to read/display/log the extended message series or alternatively allow you to add PIDs on your own (good luck here).

I hope no OBD engineers read this rudimentary explanation and hunt me down for minimalizing their work.
 
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