42RLE transmission question about hard shifts

Peter Panagakos

TJ Enthusiast
Joined
Oct 3, 2017
Messages
214
Location
Rio Rancho, NM, United States
I have a 2006 I think an X. It has the 4.0 Engine, 42rle Trans and 3.73 axles. I just noticed the last two times I drove the Jeep the first transmission shift was very noticeable. Before the trans shifting has always been very smooth. It only did this the last two times I drove it, and only at first in the morning. That first shift was I guess you would call it a hard shift. After that it went back to being as smooth as usual. I recently went to moab wheels with 31"tires, but I had 30" tires before that for a long time. I can't afford a gear swap right now, and I only drive around town with the top off, no offroading at all, just like Jeeps in the summer. The only change I made is to cancel the over drive first thing before I take off. The fluid is very clear and pink, no burn smell. Does the first shift doing this mean something, or should I perhaps do a fluid change. Any opinions will help. I have nevr understood auto transmissions and this is the first I've had in a Jeep.
 
Mine does this occasionally when cold too, but I am at 150k miles. Honestly, I don't pay it a lot of mind. I flushed the transmission as best I could last year and replaced the filter which helped the overall performance. If it is a little cranky when it is cold, I am just writing it off as an old transmission with a lot of miles. Someday it will give up the ghost and need to be rebuilt, but at this point, if all it does is bang a shift now and then before it gets a little heat in it, I figure I am ahead of the game. It might do that for another 100k miles, and that will be just fine with me.

If the fluid looks clean, things are probably just fine. But, if you are interested, what I did with mine was, I took it to the local Jiffy Lube, where they claim to do a complete flush of the trans, but they do not service the filter. And their procedure, probably does replace more fluid then I would get by just dropping the pan. They run a tube down the filler and pump out the pan. Then they refill with fresh fluid and run the engine, cycling it through the gears. Then they stop, pump out the pan and refill again, and run the Jeep again. I think they did this 4 or 5 times, so a pretty good process for replacing the old fluid with new, even if the new fluid might be slightly diluted with old fluid. Then, I drove the Jeep for about 100 miles, and dropped the pan myself, changed the filter, and refilled. My thought process was that, when Jiffy Lube added a bunch of new fluid, the fresh batch of detergents may have begun to loosen deposits gummed up in the trans. So I figured the old filter would suffice to capture that mess, if there really was any, rather than clogging up a brand new filter. That's why I drove the Jeep a bit prior to dropping the pan and replacing the filter. And it really did seem to make a difference. Since this trans is really getting some miles on it, I may do another filter and fluid change this year, just to do whatever I can to prolong its life.
 
I have 117,000 miles on mine and I am the second owner. I like your advise on this. I think I will go the Jiffy Lube route first. My trans actually works very well and this is the only time I've evn noticed a gear change. Thanks.
 
Has anyone ever added any ATF to it that wasn't ATF+4? The ONLY correct type of ATF to use is ATF+4. If it doesn't say ATF+4 in big letters on the front label it's the wrong stuff. Nope, not even Mobil-1 ATF is the right stuff.
 
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Mine does strange stuff sometimes, I don't worry about it.

I run mine almost a quart high, at a minimum make sure it's full.

I would not do jiffy lube no matter what on mine. That transmission is an easy 2K+ rebuild and one moron at jiffy lube and that's what you'll be looking at. Find a really good transmission shop or a mechanic that you trust to do anything on a 42RLE. Really just my opinion but I worry about those guys just doing an oil change and that's one bolt and a filter.
 
I just checked the trans fluid level with the engine running in park and found it is a bit low, The fluid comes up top the second hole on the dip stick from the top. The area marked hot is not showing fluid. Is it possible I should add fluid first, since the fluid look very clear and pink, no smell. And is it possible to just add some fluid through the dip stick tube with a small funnel?
 
As I posted the other day, I have noticed that the TJ's first shift of the day is very noticeable. It has been this way since I changed from 15" wheels rims with 30" tall 10.5" wide tires to the 16" moab wheels with 31" tires. I started turning off the Overdrive first thing. Before I forget I have a 2006 TJ with the 4.0 motor and 42rle Trans, 3.73 axles. I checked the fluid level yesterday, engine running in neutral and found it was low. Had to add about 1 pint of ATF+4. The trans shifts quite smoothly, but the first shift in the morning I assume when the fluid is cold I can feel. I guess it's a hard shift, but it only happens with the first shift from 1st to 2cnd. After that all smooths out and it shift smooth like it always had before. Is it unusual for the shift to be harder before the fluid warms up? The fluid looks very good, clear, pink, no smells. These kinds of things bug me so anyone who has experience with the 42rle trans, please let me know what you think. I have checked everything I can think of and see nothing wrong, clean fluid, it's full now, no loose bolts or any other weird stuff. No error codes. Thanks in advance for any input on this. I should mention I have 117,000 miles, but the Jeep is well cared for and runs great. It has an easy life, no offroading as I too old for that now. I just drive it around town in the warm weather with the top off.
 
The 42rle does use a different shift schedule when cold versus hot and will alter the shift rpm. I'm pretty picky and while I notice a change in the rpm shift point when cold, I don't notice much of a change in the shift firmness. I dont want to be an alarmist but have you scanned for any codes? Many tranny codes may not set off the check engine light.
 
Not all transmission codes trigger a CEL and not all code readers can read transmission codes.

Be sure you use a scan tool that can read transmission codes.

Note: If the first 1-2 shift of the day feels just "a bit" hard it is probably nothing to worry about. However, if it is shifting with a "bang" or is jarringly hard you may want to start learning about hard 1-2 shifts with the 42RLE when cold that can be traced to a faulty PCM in some 05-06 models.

One such thread that comes to mind is here: https://www.********forum.com/f210/1st-to-2nd-hard-shifts-when-cold-2006-lj-1755777.html [Replace ******** with wrangler]
 
I had the scan done and it showed no codes. I read about the PCM problems on some model in 2005-2006 and I do have a 2006. Just odd that I never noticed this shifting thing until the last few times I drove it. Could putting taller wheels and tires effect the shifting? I'm not liking this trans anymore.
 
I have the same problem when it’s over 80 degrees outside and it probably is the pcm. I don’t have the problem the rest of the year. Only happens first or second shift and then goes away until the car is fully cooled off and started hours later where it will happen again. If you pull the positive battery lead off and ground it for 30 seconds it will clear the programming and it will shift ok for a few days before it starts doing it again in my instance as the PCM relearns the program. PCM is a hard to find part because they aren’t made any longer and you have to send for repair or buy a rebuilt module.
 
I have the same problem when it’s over 80 degrees outside and it probably is the pcm. I don’t have the problem the rest of the year. Only happens first or second shift and then goes away until the car is fully cooled off and started hours later where it will happen again. If you pull the positive battery lead off and ground it for 30 seconds it will clear the programming and it will shift ok for a few days before it starts doing it again in my instance as the PCM relearns the program. PCM is a hard to find part because they aren’t made any longer and you have to send for repair or buy a rebuilt module.
A few threads you might be interested in:

https://wranglertjforum.com/threads/05-06-pcm-issue-is-solved.21699/
https://wranglertjforum.com/threads/2005-2006-jeep-wrangler-pcm-problem-fixed.23938/
A handful of folks have had success already.
 
To K8Hockey, I have had the Wrangler Fix PCM in for the last few weeks, about 450 miles now. it works. I have no hard shifts and all works as it should. I suggest without reservation, go to 05-06 PCM issue is solved and order the PCM. It's well worth it. Talk to Mark, all he needs is your VIN to build you a new PCM.
 
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I paid $577 sent to Rio Rancho New Mexico. There was no core, just plug and play. Took about 1 week to receive it. Came with a one year warranty and I think I had the option to get an extended warranty for another $75 if I remember right. I am very pleased with this company and their product. I battled with the hard shift problem for some time. Got sick of unplugging my battery every four days.
 
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Just checking on how the new PCM is working out? I am getting the hard shift from 1 to 2 only on the first shift after it has been started. Even if I only shut it off for 2 minutes it will give me a bang shift into 2nd then its good until I do a restart. All help welcome and thank you.
 
Just checking on how the new PCM is working out? I am getting the hard shift from 1 to 2 only on the first shift after it has been started. Even if I only shut it off for 2 minutes it will give me a bang shift into 2nd then its good until I do a restart. All help welcome and thank you.

Could be you need a transmission rebuild or your fluid is low also.