Early / Erratic Shifting

[Mora]

2005 SE Auto 4.0L 65k

I was driving earlier and when my car shifted something felt off. It felt like it was erratic and like it was shifting too early. It seemed like there was a loss of power and while I do have 4.88s on 35s, I’ve never felt it shift like this before. I had someone who was in the car record for me and this is what it is was like. Let me know what you guys think. What could be the issue?

 

[Chris]

I don't know, seems normal to me.

You have a 42RLE with 35s and a bad gear ratio. I'm assuming the overdrive isn't turned off either?

Welcome to the misery that is the 42RLE

Turn the overdrive off anytime you get in the vehicle (this is the best thing you can do).

You should ideally have 5.38 gears, but unfortunately without a Rubicon Dana 44 in the front, the biggest you can fit is 5.13.

4.88 is not a good ratio for that setup, but it will have to do.

 

[CharlesHS]

I would check your ATF level first...
IF the fluid level appears good; then check the transmission wiring harness for chafes and dirty electrical connections.

 

[AjRagno]

The first video appears to show the 1-2 upshift and then the RPMs drop. You should be able to hold 2nd gear longer while accelerating. I think that the PCM is operating in extreme overheat mode and locking up the torque converter in 2nd gear. My '05 LJ developed a similar shift pattern if I drove, then parked for a few hours, then drove again. When this became an every day occurrence, I replaced the PCM. That was several several thousand miles back and it hasn't been an issue since.

With overdrive off, the 42RLE will lock the TCC immediately after the 2-3 shift. If you leave overdrive on, the TCC won't lock up until after the 3-4 shift. Not related to your issue but my advice would be to leave overdrive on until after the 2-3 shift occurs. Then turn overdrove off while still accelerating in 3rd but before the 3-4 shift occurs. The will allow the TCC to lock up in 3rd but at a high enough RPM that it will hold until you get up enough speed that the TCC will lock up and hold in overdrive. With your setup though, I don't think the TCC will hold in overdrive unless you're going down hill. Just wait to turn off overdrive until you're in 3rd gear.

What you're experiencing is not normal.

 

[Jerry Bransford]

2005-6 PCMs have the transmission control module into them and they're known for problems. I'd give Mark a call at www.wranglerfix.com and tell him what's going on, he can tell you if your issues are PCM related or not. His company has reprogrammed the bugs out of the TCM and they have earned a solid reputation for their solution.

 

[Mora]

Turn the overdrive off anytime you get in the vehicle (this is the best thing you can do).

You should ideally have 5.38 gears, but unfortunately without a Rubicon Dana 44 in the front, the biggest you can fit is 5.13.

Yes, OD was on in this instance. When off I usually run at about 2400 RPMs at 50mph. When going 75 with OD on the RPMs are at around 2500/2600.
I have a Dana 44 in the rear and a Super Dana 30 in the front. As this is my first jeep I’m very curious what 5.38 gears feel like.

 

[Mora]

I would check your ATF level first...
IF the fluid level appears good; then check the transmission wiring harness for chafes and dirty electrical connections.

I will have to check in the morning. I installed an aux transmission cooler and when I checked ATF levels at the time everything seemed fine. This was about a week ago but you never know. I’ll make sure to check in the morning.

With overdrive off, the 42RLE will lock the TCC immediately after the 2-3 shift. If you leave overdrive on, the TCC won't lock up until after the 3-4 shift. Not related to your issue but my advice would be to leave overdrive on until after the 2-3 shift occurs. Then turn overdrove off while still accelerating in 3rd but before the 3-4 shift occurs. The will allow the TCC to lock up in 3rd but at a high enough RPM that it will hold until you get up enough speed that the TCC will lock up and hold in overdrive. With your setup though, I don't think the TCC will hold in overdrive unless you're going down hill. Just wait to turn off overdrive until you're in 3rd gear.

What you're experiencing is not normal.

Oh okay that makes a bit more sense. Hopefully this is just a PCM issue and nothing wrong with the transmission itself. Just bought the Jeep about 3 months ago.

 

[Chris]

Yes, OD was on in this instance. When off I usually run at about 2400 RPMs at 50mph. When going 75 with OD on the RPMs are at around 2500/2600.
I have a Dana 44 in the rear and a Super Dana 30 in the front. As this is my first jeep I’m very curious what 5.38 gears feel like.

Yep, always get in the habit of turning OD off whenever you start it up. The thing is that that pesky .69 OD gear ratio is absolutely horrid. No matter how deep you gear, you just can't get rid of the fact that it always wants to shift into 4th gear way before it actually needs to. The only way around this is to simply turn OD off anything you start the vehicle and make this a habit.

5.38 gears would feel much better than the 4.88 gears. It still wouldn't be perfect, but 5.38 is considered the ideal gear ratio for your 42RLE running 35s. Of course like I said, the unfortunate part is they won't work unless you have a Dana 44 up front and in the rear, like Rubicon models. With your current setup, the lowest you could run is 5.13.

 

[AjRagno]

I would encourage anyone with the 42RLE to go out and perform their own test by accelerating from a stop with O/D OFF and with O/D ON. You'll find that with O/D OFF, the TCC will lock up immediately after the 2-3 shift occurs. With O/D ON, the TCC will remain unlocked in 3rd gear and lock immediately after the 3-4 shift occurs. I'm not saying that we should leave O/D ON or OFF, rather that we need to know when to leave it ON and when to turn it OFF.

In the first video above, if the drop of RPMs down below 2,000 is happening after the 1-2 shift, I would still say that the PCM has placed the transmission in extreme overheat mode. On the other hand, if this drop in RPMs is happening after the 2-3 shift then it's because O/D had been turned OFF before the transmission shifted into 3rd and this drop is due to the TCC locking up in 3rd gear.

I've had my LJ since 2012. Since purchase, it's been driven just about every day, over 170,000 miles. For the first 6 months I followed the advice to turn O/D OFF unless I were on the freeway. Without considering the shift behaviors at the time I noticed 2 quirks: The first was that there was a sudden dropped in power after the transmission shifted from 2nd to 3rd, like a dead spot. The 2nd was that the transmission would lug at 30 MPH, even violently if going up hill.

If you start out with O/D OFF, the TCC will immediately lock up after the 2-3 occurs. If you've reached your target speed, fine, you'll only end up lugging the engine. If you to continue accelerating however, the TCC is going to unlock. Now instead of the transmission only performing a single action, it's performed 3: 2-3 shift, TCC lock, TCC unlock, and it will do this every time it shift from 2nd to 3rd gear. If there were a predetermined number of times the TCC could lock and unlock, you'd be cutting the service life in half if always starting out with O/D OFF.

If you start out with O/D ON, the TCC will not lock up in 3rd gear (at least not immediately), keeping the direct drive, 1:1 ratio. Not only is the 2-3 shift now resulting in only a single action, your RPMs will also continue to climb while accelerating instead of dropping as the TCC locks up.

Rather that starting with O/D OFF, learn when to turn it OFF and when to turn it ON. In my experience, it's best to start with O/D ON, then turn it OFF after the 2-3 shift occurs, while still accellerating. Then, before the 3-4 shift occurs, turn O/D OFF so that the TCC locks up in 3rd with the RPMs high enough that they won't drop down below 2,000. If you're at your target speed, that's it. If you still need to accelerate you can do so with the TCC lock up in 3rd and then turn O/D back ON when you're at a speed high enough that the TCC will lock up and remain locked.

O/D OFF = TCC lock up in 3rd
O/D ON = TCC lock up in 4th

 

[Mora]

I would encourage anyone with the 42RLE to go out and perform their own test by accelerating from a stop with O/D OFF and with O/D ON. You'll find that with O/D OFF, the TCC will lock up immediately after the 2-3 shift occurs. With O/D ON, the TCC will remain unlocked in 3rd gear and lock immediately after the 3-4 shift occurs. I'm not saying that we should leave O/D ON or OFF, rather that we need to know when to leave it ON and when to turn it OFF.

In the first video above, if the drop of RPMs down below 2,000 is happening after the 1-2 shift, I would still say that the PCM has placed the transmission in extreme overheat mode. On the other hand, if this drop in RPMs is happening after the 2-3 shift then it's because O/D had been turned OFF before the transmission shifted into 3rd and this drop is due to the TCC locking up in 3rd gear.

I've had my LJ since 2012. Since purchase, it's been driven just about every day, over 170,000 miles. For the first 6 months I followed the advice to turn O/D OFF unless I were on the freeway. Without considering the shift behaviors at the time I noticed 2 quirks: The first was that there was a sudden dropped in power after the transmission shifted from 2nd to 3rd, like a dead spot. The 2nd was that the transmission would lug at 30 MPH, even violently if going up hill.

If you start out with O/D OFF, the TCC will immediately lock up after the 2-3 occurs. If you've reached your target speed, fine, you'll only end up lugging the engine. If you to continue accelerating however, the TCC is going to unlock. Now instead of the transmission only performing a single action, it's performed 3: 2-3 shift, TCC lock, TCC unlock, and it will do this every time it shift from 2nd to 3rd gear. If there were a predetermined number of times the TCC could lock and unlock, you'd be cutting the service life in half if always starting out with O/D OFF.

If you start out with O/D ON, the TCC will not lock up in 3rd gear (at least not immediately), keeping the direct drive, 1:1 ratio. Not only is the 2-3 shift now resulting in only a single action, your RPMs will also continue to climb while accelerating instead of dropping as the TCC locks up.

Rather that starting with O/D OFF, learn when to turn it OFF and when to turn it ON. In my experience, it's best to start with O/D ON, then turn it OFF after the 2-3 shift occurs, while still accellerating. Then, before the 3-4 shift occurs, turn O/D OFF so that the TCC locks up in 3rd with the RPMs high enough that they won't drop down below 2,000. If you're at your target speed, that's it. If you still need to accelerate you can do so with the TCC lock up in 3rd and then turn O/D back ON when you're at a speed high enough that the TCC will lock up and remain locked.

O/D OFF = TCC lock up in 3rd
O/D ON = TCC lock up in 4th

With this being said, are you constantly turning OD on and off while you are driving to make the TCC lock up when you want it to?

 

[AjRagno]

With this being said, are you constantly turning OD on and off while you are driving to make the TCC lock up when you want it to?

I use the switch often but it's not constant and its use depends on the driving conditions and speed I need to hold. I have 31" tires and 3.73 gears. With my tire/gear combination the transmission will shift into 4th gear (O/D) at 35 MPH and the TCC will lockup in 4th gear at 42 MPH if I'm on a flat surface and no longer accelerating. If I need to drive between 40-60 MPH, I turn overdrive off at 40 MPH. Once I get to 60 MPH, I can turn O/D back ON without lugging the engine and, unless I need to go up a hill, the TCC will remain locked. If the speed drops below 60 MPH, I turn O/D OFF. The TCC will then unlock, the transmission will shift from 4th to 3rd gear and the TCC will lockup again. When I drop down below 40 MPH, I again turn O/D back ON to keep the TCC from locking up again in 3rd gear.

With your gear and tire combination, the RPMs in 4th gear with the TCC locked up are nearly always going to be too low. I think you just need to figure out when 3rd gear with the TCC unlocked (O/D ON) vs 3rd gear with the TCC locked (O/D OFF) is better.