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Thread: NAG1 frequently doesn't downshift to 1st gear when stopping/stopped

  1. #1
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    NAG1 frequently doesn't downshift to 1st gear when stopping/stopped

    I've read a lot, and learned a lot, and believe this is a tuning issue...

    I have noticed several times that when I take off from a light, stop sign, etc. that my Jeep seems very underpowered (and it isn't.) So I smacked the shifter into Autostick and found that it was in 2nd gear. Started learning and logging and was finally able to catch it in a log.

    When I stop, the log shows the Trans Selected Gear as D, the Trans Current Gear as N. If I stay in D and start to take off it will show N for quite a while and eventually display 'Unknown' then 2nd without having set the Upshift 'Yes' bit. If I slap it into Autostick it is in 2nd and will not allow me to change it, neither up nor down, until I start moving.

    I don't believe it is an internal issue because I can downshift to 1st with the Autostick and the shift is firm. Where should I start looking for the root cause?

    You can see the first instance in the attached log at Time: 07:46:52, 00:04:36.
    Attached Files Attached Files

  2. #2
    lets see the tune?

  3. #3
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    Quote Originally Posted by Kmoney View Post
    lets see the tune?
    Dang, thought I attached the log and the tune both. Here it is
    Attached Files Attached Files

  4. #4
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    Quote Originally Posted by Kmoney View Post
    lets see the tune?
    @Kmoney I see from an old thread that you had a very similar issue. Were you able to identify the cause and fix it?

    Jan from HPT suggested that I flash the TCM back to stock, see if it goes away, then apply Trans changes one at a time to identify the issue. Between the time it takes to write the tune, and the amount I drive my Jeep (6k miles in 2 years) this approach could possibly take me months.

  5. #5
    Quote Originally Posted by Anvil15jku View Post
    @Kmoney I see from an old thread that you had a very similar issue. Were you able to identify the cause and fix it?

    Jan from HPT suggested that I flash the TCM back to stock, see if it goes away, then apply Trans changes one at a time to identify the issue. Between the time it takes to write the tune, and the amount I drive my Jeep (6k miles in 2 years) this approach could possibly take me months.
    Have you verified fluid level? Mak sure its not over filled. 2-1 down shift may be the issue. try moving that around a bit to see if it makes a difference. Im the same way. I dont drive it enough to get all the bugs out of it.

  6. #6
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    Quote Originally Posted by Anvil15jku View Post
    I've read a lot, and learned a lot, and believe this is a tuning issue...

    I have noticed several times that when I take off from a light, stop sign, etc. that my Jeep seems very underpowered (and it isn't.) So I smacked the shifter into Autostick and found that it was in 2nd gear. Started learning and logging and was finally able to catch it in a log.

    When I stop, the log shows the Trans Selected Gear as D, the Trans Current Gear as N. If I stay in D and start to take off it will show N for quite a while and eventually display 'Unknown' then 2nd without having set the Upshift 'Yes' bit. If I slap it into Autostick it is in 2nd and will not allow me to change it, neither up nor down, until I start moving.

    I don't believe it is an internal issue because I can downshift to 1st with the Autostick and the shift is firm. Where should I start looking for the root cause?

    You can see the first instance in the attached log at Time: 07:46:52, 00:04:36.
    Had a similar issue and started playing around with my shift scheduling and a few other settings. Now my JKU is shifting perfectly with my 6.4 transplant.
    Run a compare to my file... 2013 Jeep JK Sahara 6.4 ECU (MJ) + TCM (MJ) WIP3.hpt

  7. #7
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    Quote Originally Posted by JWM_Jankowitz View Post
    Had a similar issue and started playing around with my shift scheduling and a few other settings. Now my JKU is shifting perfectly with my 6.4 transplant.
    Run a compare to my file... 2013 Jeep JK Sahara 6.4 ECU (MJ) + TCM (MJ) WIP3.hpt
    Thanks! I will compare the two tonight and let you know what I find. Also just got my wideband hooked up so hopefully I can get some solid logging done now as well.

  8. #8
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    Quote Originally Posted by Kmoney View Post
    Have you verified fluid level? Mak sure its not over filled. 2-1 down shift may be the issue. try moving that around a bit to see if it makes a difference. Im the same way. I dont drive it enough to get all the bugs out of it.
    I would *hope* it isn't overfilled since it has never been touched (only 40k miles on it) but I will definitely check it out. I suppose the fluid could also be cooked

  9. #9
    I tune Chrysler / Jeep / Ram / Dodge for a living.. if I can fix your issue in one revision would you consider a full tune? lol but honestly there is a super likely possibility that you have a solenoid issue if it's taking off in second gear. Any DTC codes? Let me send you a revision either way see if it helps.

  10. #10
    Just made changes to the transmission, I notice it's boosted, wouldn't want to touch the motor side without being there..

    Transmission seemed a little aggressive.. anyhow, let me know if these changes help you with your issue. Good luck bud.
    Attached Files Attached Files

  11. #11
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    Quote Originally Posted by luciddeath View Post
    Just made changes to the transmission, I notice it's boosted, wouldn't want to touch the motor side without being there..

    Transmission seemed a little aggressive.. anyhow, let me know if these changes help you with your issue. Good luck bud.
    Thanks man! I will take a look and then give it a try later today. I do see the code U1118 (current) which doesn't make a whole lot of sense considering it is clearly communicating. I will pull the dash panel and check all of the connections to the TCM since it has been removed in the past.

    Ultimately, I suspect there is some bad scaling in the current tune to help correct for my extra deep gears (5.38's) and it was never commanding the 2-1 downshift (as seen in the log.)

    I still don't have a good grasp as to how to go about correcting for the output shaft speed difference with the deeper gears. I know something needs to be scaled but not understanding where to do that. My final drive ratio is ~7% shorter than it was from the factory... (now: 5.38's and 40's (38.75 actual) vs stock: 4.10 and 31.5)
    Last edited by Anvil15jku; 10-09-2019 at 01:46 PM.

  12. #12
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    Quote Originally Posted by luciddeath View Post
    Just made changes to the transmission, I notice it's boosted, wouldn't want to touch the motor side without being there..

    Transmission seemed a little aggressive.. anyhow, let me know if these changes help you with your issue. Good luck bud.
    Looks like this solved the problem. So now I get to figure out why that is.

    You didn't change much but I did see a couple interesting things in there, most notably that you solved another mystery for me. ECT max rpm above 230 degrees was set to 3800 and you corrected that. I had an issue a few weeks back after sitting in heavy traffic going up I-70 out of Denver (6-10% uphill grade) and it started cutting out on me right about 4k RPM. Pretty sure that this was the issue.

  13. #13
    Yes it was. Even tho the setting is at a high ECT it will still hit that setting. Glad I could help bud.

  14. #14
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    I appreciate it a ton. By changing only a few settings I can narrow it down a lot faster. I will probably push a few of those RPM limits back up since it still pulls hard up to 6800-7000. It was hanging a bit on the 2-3 and 3-4 upshifts at low throttle so I will take a look at those as well.

    PM me your contact info and I will, at the very least, point others your direction for their tuning needs. Hopefully that will generate some revenue for ya.

    What params would I look at to increase the throttle sensitivity, especially at very low throttle %?s (for rock crawling)?

    Time for me to learn more about the engine side now, got the AEM -0334 up and running now as well.

  15. #15
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    Quote Originally Posted by luciddeath View Post
    Yes it was. Even tho the setting is at a high ECT it will still hit that setting. Glad I could help bud.
    According to the service manual, 230 is middle of the operating range for the 3.6. I wish there was an actual gauge for coolant temp on it. But hell, can't even get a volt gauge out of them
    Last edited by Anvil15jku; 10-10-2019 at 08:40 AM.