TCM replacement on '13 JKU

[Bad Sport]

Has anyone replaced the TCU on their JKU?
I want to replace mine because of delayed up shifts and the manual shift will not shift up from low. This started after installing 35" tires and regearing to 4:88. I've made the corrections using my Flashcal.
I have the replacement but want to know if the new unit needs to be programmed.

 

[OTH Overland]

Has anyone replaced the TCU on their JKU?
I want to replace mine because of delayed up shifts and the manual shift will not shift up from low. This started after installing 35" tires and regearing to 4:88. I've made the corrections using my Flashcal.
I have the replacement but want to know if the new unit needs to be programmed.

Welcome to my world .... We have a 2013 JKU Rubicon and are going thru the same issues. Upgraded to 35's and with the stock 4.10 it was drivable but struggled on hills, dropping in and out of overdrive. Transmission started to hang in 3rd gear and bang off the rev limiter when pulling a hill. around town shifting was not a good as stock, but acceptable. Dropped the money to go to 4.88's and the results were less then desirable to say the least. Overall RPM at highway speed is very close to what it was with stock tires and 4.10 gears. Purchased the Superchips FlashPaq, corrected gears and tire size, Speedo now reads right on the money. (Think I ended up with 34.5 for the tire size correction). Transmission still did not shift well, really likes to hold on to a gear before upshifting under load. (Autostick will not let me manually shift up either.) Under full acceleration on the flat it will not shift past 3rd unless I let off the gas for a moment. On hills I am screwed and stuck at 55-60 with engine screaming, steeper hills it will hit second.

I did a lot of research and many others having same issues. I did find two companies RPM Extreme and OST Dyno that sell reprogrammed TCM's. Reviews of both were pretty much hit and miss, I contacted both with what my symptoms were and if it would play nice with Superchips etc. no response from OST, and had some good conversations with RPM. Decided to go with RPM and ordered their TCM, installed it and noticed a big improvement over the around town shifting, nice and crisp at a reasonable RPM, however the wide open throttle and climbing hills were virtually unchanged. Started getting oil in my air filter which never happened before the change, but I had not taken the Jeep on a long mountainous trip since the bigger tires so I think the oil issue may be more to do with running hard at high rpm for an extended time. running around town does not seem to be creating the oil issue, so I am sure that is not the TCM fault. I am currently emailing with the rep from RPM and It looks like we are going to send the TCM back and he will adjust some parameters and send it back. Hopefully I will have some better results.... Not sure if I will try the OST Dyno TCM if I do not get results out of the one from RPM or not, gets expensive, but not happy with how it runs now, and willing to do what it takes to make it shift normal(ish).

Had thought about purchasing an HP Tuner and having a go at programming it myself, but after reading many hours of posts on wrangler and HP Tuner forums, no one else seems to be having any success. At least with my own tuner, I could keep tweaking one variable at a time until I find something that works. Other thoughts have been a 8 speed auto conversion, or a Hemi/8 speed swap...lol

 

[Bad Sport]

Welcome to my world .... We have a 2013 JKU Rubicon and are going thru the same issues. Upgraded to 35's and with the stock 4.10 it was drivable but struggled on hills, dropping in and out of overdrive. Transmission started to hang in 3rd gear and bang off the rev limiter when pulling a hill. around town shifting was not a good as stock, but acceptable. Dropped the money to go to 4.88's and the results were less then desirable to say the least. Overall RPM at highway speed is very close to what it was with stock tires and 4.10 gears. Purchased the Superchips FlashPaq, corrected gears and tire size, Speedo now reads right on the money. (Think I ended up with 34.5 for the tire size correction). Transmission still did not shift well, really likes to hold on to a gear before upshifting under load. (Autostick will not let me manually shift up either.) Under full acceleration on the flat it will not shift past 3rd unless I let off the gas for a moment. On hills I am screwed and stuck at 55-60 with engine screaming, steeper hills it will hit second.

I did a lot of research and many others having same issues. I did find two companies RPM Extreme and OST Dyno that sell reprogrammed TCM's. Reviews of both were pretty much hit and miss, I contacted both with what my symptoms were and if it would play nice with Superchips etc. no response from OST, and had some good conversations with RPM. Decided to go with RPM and ordered their TCM, installed it and noticed a big improvement over the around town shifting, nice and crisp at a reasonable RPM, however the wide open throttle and climbing hills were virtually unchanged. Started getting oil in my air filter which never happened before the change, but I had not taken the Jeep on a long mountainous trip since the bigger tires so I think the oil issue may be more to do with running hard at high rpm for an extended time. running around town does not seem to be creating the oil issue, so I am sure that is not the TCM fault. I am currently emailing with the rep from RPM and It looks like we are going to send the TCM back and he will adjust some parameters and send it back. Hopefully I will have some better results.... Not sure if I will try the OST Dyno TCM if I do not get results out of the one from RPM or not, gets expensive, but not happy with how it runs now, and willing to do what it takes to make it shift normal(ish).

Had thought about purchasing an HP Tuner and having a go at programming it myself, but after reading many hours of posts on wrangler and HP Tuner forums, no one else seems to be having any success. At least with my own tuner, I could keep tweaking one variable at a time until I find something that works. Other thoughts have been a 8 speed auto conversion, or a Hemi/8 speed swap...lol

Hi Dave thanks for your response. I also have the FlashPaq and set my tire size at 34.5 as well. I have 4:88 gears and a 2.5 lift.
I tried everything other than taking it to a dealership. However, today I found out how to reset the TCM so I reinstall my old unit and reset it. It seems to be running great although I haven't been to the hills yet. Manual shifting is working again so that's good news. Maybe I'll see better gas mileage which was another issue.
If you want to try the reset it's pretty simple. Remember that it is important after the first step not to open a door or touch any switches for at least 2 minutes.
First turn the key on (not start) then depress the accelerator to the floor and hold for 30 seconds. Turn the key off then release the accelerator. Now sit and don't open the door or mess with any switches for at least 2 minutes (I waited 3). Supposedly you should hear a click when it's finished resetting but I didn't hear it. After the 2 minutes you can fire it up and drive.
I haven't had oil issues concerning this issue but I did have the engine oil cooler/filter unit fail which dumps oil in the valley of the intake manifold a couple weeks ago. The OEM unit is made of plastic (pretty dumb) but I replaced it with aluminum. So far so good.
Let me know how that hemi swap goes. I've though about the 8 speed swap but I'm retired now and would rather spend my money out on the trail.

 

[OTH Overland]

Hi Dave thanks for your response. I also have the FlashPaq and set my tire size at 34.5 as well. I have 4:88 gears and a 2.5 lift.
I tried everything other than taking it to a dealership. However, today I found out how to reset the TCM so I reinstall my old unit and reset it. It seems to be running great although I haven't been to the hills yet. Manual shifting is working again so that's good news. Maybe I'll see better gas mileage which was another issue.
If you want to try the reset it's pretty simple. Remember that it is important after the first step not to open a door or touch any switches for at least 2 minutes.
First turn the key on (not start) then depress the accelerator to the floor and hold for 30 seconds. Turn the key off then release the accelerator. Now sit and don't open the door or mess with any switches for at least 2 minutes (I waited 3). Supposedly you should hear a click when it's finished resetting but I didn't hear it. After the 2 minutes you can fire it up and drive.
I haven't had oil issues concerning this issue but I did have the engine oil cooler/filter unit fail which dumps oil in the valley of the intake manifold a couple weeks ago. The OEM unit is made of plastic (pretty dumb) but I replaced it with aluminum. So far so good.
Let me know how that hemi swap goes. I've thought about the 8 speed swap but I'm retired now and would rather spend my money out on the trail.

I tried talking with my local dealership and they are saying the issues are likely caused by bigger tires/gears/lift/weight etc and do not want anything to do with trying to fix it. Might take it to a transmission shop and have them run it through their computer test to see if there are any internal issues, not thinking so as it shifts properly during normal driving etc, and no codes (that I can read anyway), trans temp is good so pretty sure its some type of programming problem. Thank you for the reset directions, I tried this the other day but the directions did not include holding it to the floor for 30 seconds. Will try again today. My first impression was that this just cleared out the adaptive learning that the computer does while you drive, so figured it would likely just go back to what it was after a few drives, however I did read last night that it forces the computer to talk with the PCM and download tire/gear ratio information and this is otherwise not passed down to the transmission. If this is true and it thinks I am on stock tires/gears it could be what is causing the problem since the transmission calculates its shift points from tail shaft rpm not engine rpm and that requires final drive ratio to be factored in. Worth a try at least.

We went for a long drive yesterday to do some testing. 1st to 2nd and 4th to 5th shifts seem to work all the time both with me driving and on cruise control. under full throttle or pulling a hill 2nd to 3rd and 3rd to 4th refuse to upshift even after cresting the hill. I have to let off the throttle or disengage cruise to get it to upshift. downshifts seem to happen to early. If the reset does not fix it, and I can't get RPM to modify their programming I will buy a tuner and take a go at it myself. I have learned that simply changing the variables for what rpm is shifts at does not solve the problem as the transmission computer looks at the PID for engine torque and if the engine is not far enough into its torque curve it will not allow an upshift even though maximum rpm has been achieved. Apparently one must delve into the upshift torque shift ramp tables and modify the amount of torque the transmission requires for a shift. Maybe by dumb luck and messing around I will figure it out. will download and keep the programming so i can go back to it if all goes bad lol.

Did check the amount of oil in the catch can I installed and it is far less than the mess in my air box indicated which is a good sign. will check the filter/box later and see if any got past the catch can.

Hoping you find good luck on the reset of your computer, looking forward to see if you have improvements once you get up in the hills.

 

[Bad Sport]

I tried talking with my local dealership and they are saying the issues are likely caused by bigger tires/gears/lift/weight etc and do not want anything to do with trying to fix it. Might take it to a transmission shop and have them run it through their computer test to see if there are any internal issues, not thinking so as it shifts properly during normal driving etc, and no codes (that I can read anyway), trans temp is good so pretty sure its some type of programming problem. Thank you for the reset directions, I tried this the other day but the directions did not include holding it to the floor for 30 seconds. Will try again today. My first impression was that this just cleared out the adaptive learning that the computer does while you drive, so figured it would likely just go back to what it was after a few drives, however I did read last night that it forces the computer to talk with the PCM and download tire/gear ratio information and this is otherwise not passed down to the transmission. If this is true and it thinks I am on stock tires/gears it could be what is causing the problem since the transmission calculates its shift points from tail shaft rpm not engine rpm and that requires final drive ratio to be factored in. Worth a try at least.

We went for a long drive yesterday to do some testing. 1st to 2nd and 4th to 5th shifts seem to work all the time both with me driving and on cruise control. under full throttle or pulling a hill 2nd to 3rd and 3rd to 4th refuse to upshift even after cresting the hill. I have to let off the throttle or disengage cruise to get it to upshift. downshifts seem to happen to early. If the reset does not fix it, and I can't get RPM to modify their programming I will buy a tuner and take a go at it myself. I have learned that simply changing the variables for what rpm is shifts at does not solve the problem as the transmission computer looks at the PID for engine torque and if the engine is not far enough into its torque curve it will not allow an upshift even though maximum rpm has been achieved. Apparently one must delve into the upshift torque shift ramp tables and modify the amount of torque the transmission requires for a shift. Maybe by dumb luck and messing around I will figure it out. will download and keep the programming so i can go back to it if all goes bad lol.

Did check the amount of oil in the catch can I installed and it is far less than the mess in my air box indicated which is a good sign. will check the filter/box later and see if any got past the catch can.

Hoping you find good luck on the reset of your computer, looking forward to see if you have improvements once you get up in the hills.

I went for a drive and it seems to shift fine even in the hills. BUT now I have a code, DTC PO753, Trans 3-4 Shift Sol/Trans Relay Circs. Strange because it seems to shift fine. I think I'll reset to factory settings and start over.
This morning I have another code, DTC PO198, Engine Oil Temp Sens Hi. I'm guessing this is related to having the oil cooler replacement. I'm waiting to hear from the shop now. I'm pretty sure to get to the sensor they'll have to tear down to the intake manifold again so I'm going to stop by the parts house and pick up new temp and pressure sensors. Should have had them replaced while they had it apart but didn't think about it.
Hope I can get this straightened out because I have a Death Valley trip scheduled in a couple weeks.

 

[OTH Overland]

Sometimes resetting or changing a part will kick off a few codes for no reason, or perhaps a connector was not pushed all the way in on the sensor, had that last time I pulled my intake and did not get the air temp sensor all the way plugged in and popped a code. Worth a try to reset the codes and do another drive. Some of the codes like engine miss fire will reset themselves after 3 successful drive cycles. I think the PO753 error results from the transmission valve body and a solenoid or its controlling relay either stick or get an out of range voltage might be a gremlin from the reset that will not come back if you clear the codes, or could be an indication of early failure, the good shifting and recent reset seem to push toward the gremlin rather than the latter. Have not had time to do the reset and test drive yet, hoping on Friday. Also bit the bullet and purchased a HP Tuner with some credits and a book on how to program transmissions, so will have a go at it if the reset does not work. Did you do the retraining after the reset, where you coast down from fifth to 1st and then up from 1st to fifth at 1800 rpm or just the reset. See mixed reviews that say the trans learns faster and more accurate if you do that, but will figure it out eventually if you don't.

Have fun in Death Valley, that's where we were for Thanksgiving when we started having more trouble with trans and oil in air filter. Had a blast down there, just not enough time to really explore. Tried to stay away from anything to risky as we were solo, mengal pass was about the most technical thing we did.

 

[MazeVX]

Has anyone replaced the TCU on their JKU?
I want to replace mine because of delayed up shifts and the manual shift will not shift up from low. This started after installing 35" tires and regearing to 4:88. I've made the corrections using my Flashcal.
I have the replacement but want to know if the new unit needs to be programmed.

The transmission is just poorly programmed by jeep, over here it's quite common to get the tcu reprogrammed. Drives like a different vehicle after reprogramming, transmission works as it should and stays cooler.

 

[OTH Overland]

The transmission is just poorly programmed by jeep, over here it's quite common to get the tcu reprogrammed. Drives like a different vehicle after reprogramming, transmission works as it should and stays cooler.

So far have purchased a custom programmed TCM from a company here that really made no difference, there is one other option, but going to try and tweak it myself before paying for another TCM.

 

[MazeVX]

Okay that's not nice. I got mine reprogrammed along with some careful modifications to the engine software, the guy applied changes, I did a test drive and we changed it again, after 2 rounds we both were satisfied and I think it's the best within the possible limits of the transmission (5th still to short...)
We changed shifting points, shifting strategies and converter handling, both in the normal stage and the performance stage and modified the torque curve to better fit the gearing of the transmission, now I do have a turbo diesel so we had lot more room to play with the engine but transmission is the same WA580 nag1.
Now this is nothing you can do on your own in my opinion, the guy has decades of experience and knew things about the transmission I didn't even know existed (but he was right I checked it)
We also have a company where you can send your tcu and get it back reprogrammed and it basically do the same, no matter if gas or diesel it works wonders. Probably a matter of finding the right person, 90% of the issues can definitely be solved with the software.

 

[OTH Overland]

Okay that's not nice. I got mine reprogrammed along with some careful modifications to the engine software, the guy applied changes, I did a test drive and we changed it again, after 2 rounds we both were satisfied and I think it's the best within the possible limits of the transmission (5th still to short...)
We changed shifting points, shifting strategies and converter handling, both in the normal stage and the performance stage and modified the torque curve to better fit the gearing of the transmission, now I do have a turbo diesel so we had lot more room to play with the engine but transmission is the same WA580 nag1.
Now this is nothing you can do on your own in my opinion, the guy has decades of experience and knew things about the transmission I didn't even know existed (but he was right I checked it)
We also have a company where you can send your tcu and get it back reprogrammed and it basically do the same, no matter if gas or diesel it works wonders. Probably a matter of finding the right person, 90% of the issues can definitely be solved with the software.

Had the NAG1 in my Jeep Commander and I loved it, was super responsive and the manual shifting function worked really well, transmission just did what you asked as long as you did not exceed the overarching parameters of course that had a 4.7 engine ahead of it instead of the 3.6 the JK has. I am no means a professional tuner, but do have some experience with modifying engine tunes, and have done a lot of research on why this transmission behaves the way it does. Plan on saving the tune that is from the factory and hopfully the one that came on the second TCM, that way I can put it back to where it is , should I go astray with my feeble poking around. I do not have anyone local that we can go through the tune / test and repeat until its correct, much more difficult with having to mail it across country and have the tuner understand the issues third hand. At least this way I will have the tools to be able to data log what the transmission is doing in real time and forward the results and graphs to a professional tuner somewhere and then be able to reload the tune without mailing all over.

 

[MazeVX]

Yes I should have said that we were at the tuners workshop, had zero interest in mailing back and forth I totally understand you.
Well then you should be able to do it on your own, and you probably already know what you want to change.
That's basically what I did with the guy, we talked about what I don't like and how I want it and he did what was possible and made sense.

When they did the commander the Mercedes engineers were in duty of the programming, when they came out with nag1 in the jk those guys were far away and the jeep engineers were obviously not up to the task...

 

[OTH Overland]

Yes I should have said that we were at the tuners workshop, had zero interest in mailing back and forth I totally understand you.
Well then you should be able to do it on your own, and you probably already know what you want to change.
That's basically what I did with the guy, we talked about what I don't like and how I want it and he did what was possible and made sense.

When they did the commander the Mercedes engineers were in duty of the programming, when they came out with nag1 in the jk those guys were far away and the jeep engineers were obviously not up to the task...

I agree fully, I have had Jeeps from most of the famous and infamous management companies that have owned the brand 42 Willys MB, 48 Willys CJ2A, 57 Willys Jeep Pickup, 74 CJ5 (AMC), 2007 Jeep Commander (Daimler) and currently have 2000 WJ (Daimler) and 2013 JK (FCA) hands down the Daimler years were the best in my experience. Sold the Commander with 220k on it and no issues except both axles rebuilt, WJ has been totaled and still going strong at 225k with no plans on selling it, JK is awesome off road but requires many 'fixes' to make it worthy of safely travelling solo far off the beaten path. For all its faults though I love it and will work thru them to make it ours. I have owned a few Harleys also including one from the AMF years (a company who made bowling balls...lol) again a vehicle that is arguably not the most reliable, but produces a very unique driving experience that (almost) makes us forget the little its a Harley thing or a Jeep thing...lol I am a stubborn creature and will continue on finding ways to improve the weird choices I make in vehicles even if I end up emptying my wallet in the process...lol

 

[MazeVX]

I agree fully, I have had Jeeps from most of the famous and infamous management companies that have owned the brand 42 Willys MB, 48 Willys CJ2A, 57 Willys Jeep Pickup, 74 CJ5 (AMC), 2007 Jeep Commander (Daimler) and currently have 2000 WJ (Daimler) and 2013 JK (FCA) hands down the Daimler years were the best in my experience. Sold the Commander with 220k on it and no issues except both axles rebuilt, WJ has been totaled and still going strong at 225k with no plans on selling it, JK is awesome off road but requires many 'fixes' to make it worthy of safely travelling solo far off the beaten path. For all its faults though I love it and will work thru them to make it ours. I have owned a few Harleys also including one from the AMF years (a company who made bowling balls...lol) again a vehicle that is arguably not the most reliable, but produces a very unique driving experience that (almost) makes us forget the little its a Harley thing or a Jeep thing...lol I am a stubborn creature and will continue on finding ways to improve the weird choices I make in vehicles even if I end up emptying my wallet in the process...lol

I totally feel you!
Even though I can not complain about the reliability of the my jk, only the front axle gives me a bit trouble and replacement over here is even more expensive than in the US... The only major issue was around 150.000km where we found a coolant leak that turned out to be very expensive to repair but I could still have driven it out of the wild, which is in my opinion the only valid point.

 

[OTH Overland]

@Bad Sport, did you ever get your JK transmission TCM issues sorted out? Did you make it to DV, and did it work better?