Interesting issue with the 2012 TJs with auto tranny

#1
ARTICLE

2012 JK Wranglers equipped with the A580 automatic transmission, who change their gear ratio will cause the transmission to enter “Limp Mode”… The 2012 Jeep Wranglers with the new Pentastar 3.6L enginehit dealer lots earlier this month. The great news is that Jeep can’t keep them on the lots. The bad news is dealership can’t keep them out of the service bays. The first mod most Jeeps owners make to their Wrangler is to throw a lift kit and a set of over sized All Terrain (AT ) or Mud Terrain (MT) tires on their Jeep. -The next is to switch out the ring and pinion in the Dana 30 or Dana 44 to a more favorable gear ratio.

This is when thing go bad for 2012 JK Wranglers equipped with the A580 automatic transmission. Owners who change their gear ratio will cause the transmission to enter “Limp Mode”. -A safety program the transmission controller defaults to when its senses a change in gear ratio or damaged axle. It is designed to keep Jeep a disabled Jeep in 1st and 2nd gear so it can get home, or to the local dealership, or service station. The bad news? Currently there is no fix. Dealerships can’t override the fail safe. Jeep owners are stuck waiting for Jeep or aftermarket companies like AEV or ProComp to come up with a solution. Jeep has yet to announce a fix for the issue, and most owners have been surprised to discover that its not a warranty issue, due to the fact that the aftermarket part has caused the error.

AEV Press Release:

Warning: Changing gears on a 2012 JK will cause it to go into limp mode.

2012 JK Wranglers now include the A580 transmission. With this new trans comes a new trans controller, and unfortunately this controller is programmed to put the vehicle into limp mode if it senses a change in gear ratio. Even a Jeep dealer cannot override this.

AEV has a fix for this and we are currently working on integrating it into our ProCal Module. In the meantime, we recommend that you hold off on changing the gears in any 2012s.

We expect ProCals with the updated code to be available by the end of September. Stay tuned, we’ll send another newsletter as soon as the updated ProCals are available.
 

WolfGT

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#6
What about putting the original gears back in? Will that get it all back running smooth until the fix is released or an after market part?
 
#7
Yeah they can put the gears back in but they will have to set everything up from scratch. So the owner will have paid twice, have a lift and new tires and a turd for performance.
 
#9
Its an engine RPM vs Wheel Speed Sensor reading issue... AEV already has a fix for this that will be out this month bundled with its Pro Cal.


EDIT. Sorry I just noticed the OP's AEV info
 
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#10
Its an engine RPM vs Wheel Speed Sensor reading issue... AEV already has a fix for this that will be out this month bundled with its Pro Cal.


EDIT. Sorry I just noticed the OP's AEV info
OK that I understand. You just cleared it for me. I did not understand what the OP was saying.
 
#12
This is actually a common design. The PCM uses CPS-TISS-TOSS-WSS all to monitor speed and RPM. The 42rle trans had a similar system, but without the WSS input to tell the PCM what the final drive was doing. That's why the 42rle is bypassable. The WSS is what's causing the issue, so basically AEV has built a bypass for the TOSS, and WSS.
 
#13
seems llike they could just tweek the wheel speed sensor ie. a gear tooth spacing change to match stock wheel speed vs rpm. but i dont know anything about the trans in those things, doesnt jeep know about K.I.S.S (keep it simple stupid)?
 
#14
seems llike they could just tweek the wheel speed sensor ie. a gear tooth spacing change to match stock wheel speed vs rpm. but i dont know anything about the trans in those things, doesnt jeep know about K.I.S.S (keep it simple stupid)?
If it were only that simple.
The easy way to explain it is that the PCM is monitoring the engine rpm at the crank, the transmission input shaft rpm, the output shaft rpm, and the rpm of each wheel. It's taking all of this and adjusting shift pattern, torque converter lock, looking for ABS trigger, and a few other things. The problem is that the PCM operating system was never designed to be adjusted, as well as the fact that the data it's monitoring has some very minute tolerances. Any anomaly will trigger the PCM to react.
 
#15
If it were only that simple.
The easy way to explain it is that the PCM is monitoring the engine rpm at the crank, the transmission input shaft rpm, the output shaft rpm, and the rpm of each wheel. It's taking all of this and adjusting shift pattern, torque converter lock, looking for ABS trigger, and a few other things. The problem is that the PCM operating system was never designed to be adjusted, as well as the fact that the data it's monitoring has some very minute tolerances. Any anomaly will trigger the PCM to react.
I see said the blind man, kinda stupid on jeeps part
 
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