My 2006 TJ with 4.0, 42rle and 3.73 axles had the hard shift problem after I went to 16" moab wheels and 31" tires. I made sure the trans fluid was good and full checking with motor running in neutral. Then I disconnected the battery for 8 hours to reboot the computer. Now it works great, no hard shifts, very smooth. I was cancelling the Overdrive but then wondered if this had any bad effect on the Computer. I stopped doing that driving in town most times at about 30 to 35 mph. Will it make any difference at that speed? I'm not noticing any diff. I am assuming it would be better to cancel the OD at higher speeds to keep the rpm higher, but not necessary in town at lower speed. Any opinions on this, do I know what I'm talking about or am I clueless?
42RLE: so far so good after battery reset
- Thread starter Peter Panagakos
- Start date
Going to 16" Moab wheels and 31" tires has nothing to do with your hard shift problem whatsoever, that's purely coincidental.
Turning off overdrive has no negative affect on the PCM at all, literally.
You're overthinking all of this, I promise (and I mean that in a polite way)
Turning off overdrive has no negative affect on the PCM at all, literally.
You're overthinking all of this, I promise (and I mean that in a polite way)
This is why I asked. Disconnecting the battery for 8 hours did correct the problem, at least for now. I guess now I will see if this fix works long term or just for a while. it's been 5 days. I heard other made it for a week and the problem came back, then a few others went for months and still ok. As you can see I know nothing about computers in vehicles.
OD won't kick in until over 45 mph or so, so below that, there's no difference. And, to the best of my knowledge, shutting it off has no other effect on shift sequence as far as the computer is concerned. As automatics go, our 42rle's are not terribly sophisticated. Your hard shifts were probably just a fluke. Mine does it now and then, and others have mentioned it happening too. Until it is happening all the time, I wouldn't worry too much. Hard shift is better than no shift!
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There are some software glitches in the 05-06 42RLE computers which became part of the PCM in 2005. Don't be surprised if the hard shifting comes back.
And FYI, it doesn't take more than a few minutes to reset the computer after disconnecting the battery which can be done by just disconnecting its negative connector. Once you disconnect the battery, you can turn the headlights on as a drain for the entire electrical system which includes the PCM and TCM. Turning the headlight switch on will finish completely discharging all of the little capacitors inside those computers that keep the memory alive that will quickly reset everything in just a few minutes at the most.
And FYI, it doesn't take more than a few minutes to reset the computer after disconnecting the battery which can be done by just disconnecting its negative connector. Once you disconnect the battery, you can turn the headlights on as a drain for the entire electrical system which includes the PCM and TCM. Turning the headlight switch on will finish completely discharging all of the little capacitors inside those computers that keep the memory alive that will quickly reset everything in just a few minutes at the most.
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Thanks. This is helpful. I won't bother with turning the OD off driving around town, and if I need to do the computer reboot once in a while a few minutes sound good. What about what I read that says to disconnect the positive battery terminal and ground it for 10 minutes, then hook it back up and then turn on the lights, turn them back off. That sounded really odd to me. I prefer the negative terminal, don't understand the positive terminal method.
Nothing knows if the negative vs. positive battery connection was disconnected, either is fine. Touching the neg/pos connectors together works too but to do that safely both need to be disconnected due to the lack of clearance in that area. Discoing just the negative battery connector and flipping the headlight switch on is just as effective and easier to do.
Just disconnect the negative side and be done with it. When you reconnect it and your clock is wrong and the radio pre-sets are gone you will know it has been long enough.
You can speed the process if you like by touching the disconnected positive and negative cables, or by turning on the headlights or whatever else strikes your fancy with only the negative cable disconnected. Or not.
You can speed the process if you like by touching the disconnected positive and negative cables, or by turning on the headlights or whatever else strikes your fancy with only the negative cable disconnected. Or not.
I like the negative with the headlight plan. Never thought I would see the day that rebooting my Jeep would help fix something. Makes me miss my old Army Jeeps.