42RLE – Harsh Shift D/R + Cold Start Shift Delay

Chipps · Aug 1, 2025

Hi all,

I’m having an issue when changing from drive to reverse and back. You can hear it changing which I never could before. It also physically moves/ wobbles the car when changing.

Also after starting off from cold it will not change up on the first gear change when it should. It over revs then surges forward when it does change gear. After this 1 event the rest of the journey it works fine.

It’s 42RLE automatic transmission with 33K miles.

I’ve uploaded a video of me shifting through from drive to reverse and back to show how it’s physically moving the vehicle. Ignore the squeak that follows the movement, it’s the seat.

Any ideas on the best place to start looking?? Solenoid & filter kit?

Thanks.

hear · Aug 1, 2025

If you let it idle in neutral for maybe 30 seconds before you put it into D and try to go, does it do the same thing?

This sort of thing is not uncommon on the 32RH, so I'm just kinda guessing about the 42RLE. I don't hear anything odd in the video, and the car low-key moving when you go into reverse is typcial of the driveline applying torque to the rear end. What's maybe more surprising is that it is a new behavior.

Chipps · Aug 1, 2025

hear said:
If you let it idle in neutral for maybe 30 seconds before you put it into D and try to go, does it do the same thing?

This sort of thing is not uncommon on the 32RH, so I'm just kinda guessing about the 42RLE. I don't hear anything odd in the video, and the car low-key moving when you go into reverse is typcial of the driveline applying torque to the rear end. What's maybe more surprising is that it is a new behavior.

Yeah still does it. Normally warm up 20-30s as a minimum.

I started noticing the harsh shifter selection a month or so ago. Only just started over revving before the first shift change of the day the last week.

macleanflood · Aug 1, 2025

What year? Do you still have the original PCM?

@Wranglerfix WranglerFix.com has fixed the endemic PCM issues on the 05s and 6s. Transmission shifting is a symptom.

-Mac

hear · Aug 1, 2025

Which is a solid reminder to OP to complete your profile.

DuckNut · Aug 1, 2025

Is that 33k original miles or since rebuild?

Chipps · Aug 1, 2025

DuckNut said:
Is that 33k original miles or since rebuild?

Original. It’s a Japanese import. Got the paperwork translated and looks like it sat unused for a bit.

Chipps · Aug 1, 2025

macleanflood said:
What year? Do you still have the original PCM?

@Wranglerfix WranglerFix.com has fixed the endemic PCM issues on the 05s and 6s. Transmission shifting is a symptom.

-Mac

2006 & original PCM.

steelhd · Aug 1, 2025

Have you properly checked the transmission fluid level?

Chipps · Aug 1, 2025

steelhd said:
Have you properly checked the transmission fluid level?

Yeah. Checked it warmed up, switched on in neutral.

DuckNut · Aug 1, 2025

Time to visit a trans shop before you tear something up.

There are times when it is cheaper to hire a professional.

Wranglerfix · Aug 2, 2025

The hard shift from 1st to 2nd is the PCM failing you. Rough idle and poor gas mileage are also common. I would not spend any money on the transmission until you change the computer. A lot of people were sold 42RLE rebuilds unnecessarily. You can call me to discuss some further detail if you would like.

Strizzo · Aug 2, 2025

Wranglerfix said:
The hard shift from 1st to 2nd is the PCM failing you. Rough idle and poor gas mileage are also common. I would not spend any money on the transmission until you change the computer. A lot of people were sold 42RLE rebuilds unnecessarily. You can call me to discuss some further detail if you would like.

Can you get poor mileage but no idle quality issues? Mine is getting high single digit mpg, but does only get driven in town on shorter trips, but the idle is butter. 5.13s and 33s (285/70-17). It just started having a harsh 1-2 shift when cold, but not sure if it’s every time yet or not since it’s only been a couple of cycles so far.

Wranglerfix · Aug 4, 2025

Yes, you can…Poor fuel economy is one of the faults of a failing computer.

Strizzo · Aug 4, 2025

Wranglerfix said:
Yes, you can…Poor fuel economy is one of the faults of a failing computer.

Got it. Is the rough shift when cold when the trans is cold or the engine is cold? I've had rough shift a few times when i start up and drive away pretty quickly, but a lot of the time i end up idling for 30 seconds to a minute, and don't have any harsh shifts. I'm wondering if my computer has been failing and its just been masked by me usually starting the engine before i get in to let the a/c get started cooling things down. The coolant temp comes up quickly but the trans temp wouldn't be very warm yet even though coolant temp is between 100 and 150 degrees.

Chipps · Aug 4, 2025

Wranglerfix said:
The hard shift from 1st to 2nd is the PCM failing you. Rough idle and poor gas mileage are also common. I would not spend any money on the transmission until you change the computer. A lot of people were sold 42RLE rebuilds unnecessarily. You can call me to discuss some further detail if you would like.

Been watching a few videos on YouTube, most of them referencing you directly, and my harsh shift issue seems quite similar.

Will your PCM work with a RHD Japanese import? And do you ship to the UK? Thanks.

Frostbite_Offroad · Sep 24, 2025

Wranglerfix said:
The hard shift from 1st to 2nd is the PCM failing you. Rough idle and poor gas mileage are also common. I would not spend any money on the transmission until you change the computer. A lot of people were sold 42RLE rebuilds unnecessarily. You can call me to discuss some further detail if you would like.

I’m currently experiencing rough shifts from 1st to 2nd gear in my 2006 LJ automatic. I was originally thinking it needed a rebuild but sounds like the PCM might be the issue. I was just curious if there was anything else I was missing. I do have a rough idle at stoplights that I haven’t been able to get rid of with the normal tuneup stuff.

Wranglerfix · Sep 25, 2025

@Frostbite_Offroad it is the computer that has failed you. We can get it to you as quickly as tomorrow and it takes five minutes to install. Your idle will be as smooth as silk, throttle response will increase, mirrors won’t shake anymore and I can feed my kids and grandson another day!

Frostbite_Offroad · Sep 25, 2025

Wranglerfix said:
@Frostbite_Offroad it is the computer that has failed you. We can get it to you as quickly as tomorrow and it takes five minutes to install. Your idle will be as smooth as silk, throttle response will increase, mirrors won’t shake anymore and I can feed my kids and grandson another day!

Haha, thanks for the quick response, you have to keeps those kids fed! I’ll be ordering one here soon.

Frostbite_Offroad · Nov 6, 2025

Wanted to say a huge thank you to Mark over at Wranglerfix.com for the great customer service and making a great product! My 2006 LJ is now shifting super smooth from 1-2nd gear and the idle is so much better. Also had the added bonus of my turn signals now clicking normal again. I did an install video if anyone wants to check out how easy the install was.

42RLE – Harsh Shift D/R + Cold Start Shift Delay

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