42RLE transmission shifts hard from 1st to 2nd gear

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Mrossj1

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I have a 2006 Unlimited with a automatic trans that has started to shift hard from 1st gear into 2nd. It happens when the jeep is typically cold and it only happens once. I checked the transmission fluid and it was very low at normal operating temps and didn't register on the dipstick. I slowly added trans fluid and kept checking to see the progress on the dipstick. I made sure it up to operating temp, put in neutral and repeatedly added about 8oz then checked to see where it was on the dipstick. I eventually got the fluid about 1/2 way between cold and hot marks on the dipstick by adding about 3/4 of the quart into the trans. Note, when hot, the fluid got to about 1/2 way between the cold and hot mark on the dip stick. Now that everything has been sitting for a few hours, the fluid level it at the hot mark. What am I missing and is this something to worry about.
 
This is a known issue that affects a small percentage of 05-06 Wranglers with the 42RLE transmissions, believed to be PCM related.

Search Google and the "other" jeep forums for "hard shift 1st to 2nd 42RLE" and you will find several threads on the topic.
 
Taken from other threads regarding this matter:

Mine did the same thing and it was the computer. In 2005/2006 they moved the transmission control module into the powertrain control module (PCM). There are several threads on here discussing the problem. First shift after shutting the Jeep off and restarting it. After that it shifts fine until it's shut off again.

I bought an aftermarket PCM online for approx. $350 that lasted two weeks. A number of other members had the same issue so I went to the dealer for the next one. It was approx. $600 but I wish I had started there rather than trying to save a few bucks on the internet PCM.
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Same issue here... my problem was pcm.

I also had random check engine codes come in on occasion that could not be repeated...

To see if this is your problem, reset your pcm. To do this, disconnect your battery terminals, turn your ignition switch on and off as if trying to start the engine 2-3 times, then reconnect battery. That may not be the official way but it works for me.

Once I reset the pcm, it shifts normal. This would work for 1000-1500 miles and it would start doing the hard shift thing again. After a couple resets, I took my 2006 LJ in to dealership and paid them around $100 to reflash the computer. I've gone around 7000 miles with no further problem.

While the reset is not the fix, it might get you by until you can fix / replace it.
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So yes, this is related to the PCM, and it's one that the dealer should be able to fix with a refresh, as it was a known and documented issue with the 42RLE for 2005 and 2006.
 
Chris said:
Taken from other threads regarding this matter:





So yes, this is related to the PCM, and it's one that the dealer should be able to fix with a refresh, as it was a known and documented issue with the 42RLE for 2005 and 2006.
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This is not usually fixed by dealer reprogramming the PCM. Note related to this 2005-06 Wrangler 4.0 A/T Transmission shift problem. Check the Engine Computer PCM which controls the shifting. Be sure to check the Harness the transmission side of the ECM or PCM controls the shifting. It is a combination computer or PowerTrain Control PCM. But the damage to the computer is often caused by a short in the harness and specifically the transmission harness as it winds around the edge of the block. Be sure to have the harness repaired or replaced or risk damaging more computers. These are really rare and expensive PowerTrain Control Computers now unfortunately. ECM To Go www.ECMtoGO.com offers On Vehicle PCM computer testing, repair and exchange PCM computers for the 2005-06 Jeep Wrangler 4.0 Auto Transmission (including Rubicon models).There is an on site test Jeep Wrangler for testing the Multiple false sensor codes issues and the automatic transmission shifting problems issue. You can send it and they can test it in a Jeep Wrangler and then either rule out the computer or if needed get it repaired or replaced. Replacements computers are now very rare for the Wranglers especially
2000-02 and
2005-06 JEEP WRANGLER PCMs IN STOCK! call 844-ECM-ToGo 844-326-8646
 
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Just thought i would share some of my experience with the 42RLE and PCM. I was having the hard shifts between 1st and 2nd, as many others have described. My transmission finally gave up and I had to replace my transmission. It was fine for a wile and then started to do the hard shifting as did the old transmission. I took the PCM out of the jeep, removed the cover, carefully removed the protective jell from the mother board, and cleaned the mother board where the conductive rubber contact meets the mother board, and the conductive rubber also. I put it all back together and it worked for about two months. During this time the wheatear had been cold but dry. At about the two month time frame I washed my jeep. And then took off to meet up with my wife for dinner. Just when I was begin to think that I had solved my problem for good, the very first shift from 1st to second was very hard, and the next same 1st to 2nd over and over again. I pulled out my scan tool and cleared all of my codes, and then it was fine for the next couple of weeks. Funny thing is, the next time it started to act up was after I had drove to the store, went in and got some goods, I come out and it had sprinkled. And I mean a very fine sprinkle, about one or two tiny drops per square foot on my jeep. And it was doing the stupide shifting again. and the next time it happened it has the exact same scenario. So at this point I was a beginning to thing that moisture in the air or on the skin of my jeep has something to do with it. But now it is doing it even if it doesn't rain. So I don't have any good news from my end. I know this was long but maybe if we all share are experiences, and attempted fixes maybe we can see some sort of correlation between us all.
 
Was having trouble with my automatic 06 TJ shifting hard from 1st to 2nd gear. It would only do it when the engine was cold, it would rev way past 2000 rpms and lurch the very first time it shifted from 1st to 2nd and the rest of the drive would be smooth(ish).

Took it to a transmission shop and they said the computer gave them a code for a bad transmission solenoid. Replaced that for $$$ and it drove fine for 2 days, then the problem returned.

Read a lot of other forums and one guy talked about the transmission fluid temp sensor, but a lot of people were saying a bad PCM.

Took it bad to transmission shop and they plugged it back into the computer and the transmission temp sensor was reading over 1000 degrees when cold. Come to find out, there was a slight oil leak and it was building up on the back of the engine block where the ground wires are. They cleaned them up and like magic, my girl ran great again. All that $$$ spent and who knows if the solenoid was actually bad.

I’m just glad she’s fixed and hope everyone can check their ground wires on the back of the block before buying a new (used) PCM.
 
Guys and galls, I finally broke down and bought a new or should I say remanufactured PCM from Flagship one, and I couldn't be happier. it cost about 520 and some change, but it works like it should and my jeep is fun to drive again. And it only takes about 10 minutes to install.
 
Mrossj1 said:
I have a 2006 Unlimited with a automatic trans that has started to shift hard from 1st gear into 2nd. It happens when the jeep is typically cold and it only happens once. I checked the transmission fluid and it was very low at normal operating temps and didn't register on the dipstick. I slowly added trans fluid and kept checking to see the progress on the dipstick. I made sure it up to operating temp, put in neutral and repeatedly added about 8oz then checked to see where it was on the dipstick. I eventually got the fluid about 1/2 way between cold and hot marks on the dipstick by adding about 3/4 of the quart into the trans. Note, when hot, the fluid got to about 1/2 way between the cold and hot mark on the dip stick. Now that everything has been sitting for a few hours, the fluid level it at the hot mark. What am I missing and is this something to worry about.
Click to expand...
I have an 06 wrangler that shifts hard between 1st and 2nd only when the vehicle is shut off and restarted, hot or cold. No engine codes until recently, and that code was a small EVAP leak. I replaced the EVAP canister that sits in front of the master cylinder and jeep has been shifting normal . Hopefully that's my cure. Advanced auto for $35.00
 
Mrossj1 said:
I have a 2006 Unlimited with a automatic trans that has started to shift hard from 1st gear into 2nd. It happens when the jeep is typically cold and it only happens once. I checked the transmission fluid and it was very low at normal operating temps and didn't register on the dipstick. I slowly added trans fluid and kept checking to see the progress on the dipstick. I made sure it up to operating temp, put in neutral and repeatedly added about 8oz then checked to see where it was on the dipstick. I eventually got the fluid about 1/2 way between cold and hot marks on the dipstick by adding about 3/4 of the quart into the trans. Note, when hot, the fluid got to about 1/2 way between the cold and hot mark on the dip stick. Now that everything has been sitting for a few hours, the fluid level it at the hot mark. What am I missing and is this something to worry about.
Click to expand...
I have an 06 wrangler that shifts hard between 1st and 2nd only when the vehicle is shut off and restarted, hot or cold. No engine codes until recently, and that code was a small EVAP leak. I replaced the EVAP canister that sits in front of the master cylinder and jeep has been shifting normal . Hopefully that's my cure. Advanced auto for $35.00
 
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