Jeep Enthusiast Forums banner

42re wont shift into 4th gear

1980 Views 44 Replies 9 Participants Last post by  zjosh93
So the other day I got my engine pretty hot, it reached the last solid white line before the red zone so about 240 degrees, i wasnt towing or anything just got hot in 109 degree weather in traffic. I drove it around some until it got back down to 210, let it idle a bit there then shut it off to avoid heat soak. When i went to drive it again i was having issues with it going into 4th gear.

The problem only lasts for about 5 minutes of driving and it basically stays in 3rd gear even if I’m driving 50+mph. I’ve gotten pretty good at telling when the transmission should shift at different speeds, usually it shifts into 4th just over 30mph. After it shifts into 4th after 5 minutes or so it shifts completely normal for the rest of the time it is running and even goes into overdrive.

There seems to be no correlation to when it decides to shift normal other than time, even if i try manually shifting or putting it in neutral.

It also doesnt matter if i shut the car off for 1 minute or 1 hour it seems to “reset the clock” after every time I start it.

I dont believe it is a mechanical problem becasue after 5 mins or so it acts completely normal, so it leads me to believe it is electrical I just dont kno where to look. I also want to solve it now before it may become a permanent problem.

So what do y’all think could be causing this? It has been in the 100+ in Texas recently and I’m wondering if its maybe a cooling feature or something i dont know. Any help would be great let me know if there’s anything i can easily check soon.
1 - 20 of 45 Posts

· Registered
Joined
·
3,622 Posts
The 42RE will stop shifting into 4th if it the trans gets too hot. Had it happen on my 93 when one of the cooler lines was kinked. You can pull the trans codes by doing the key trick and watching the OD Off light.
 

· Registered
Joined
·
3,622 Posts
95 ZJ Tranz Trouble Codes

Scroll to post 6. Trans code 16 (not the same as the check engine codes) is "Transmission fluid temperature input ". That matches your symptoms.

Now you just need to figure out if its:
  • Actually getting hot - slipping, restricted cooler flow, etc.
  • Bad wiring
  • Bad temp sensor (built into the.... governor pressure sensor IMS?
I guess a bad TCM would also maybe do that. Bad TCMs are rare but they do happen and can throw random codes.
 

· Registered
Joined
·
66 Posts
Discussion Starter · #6 ·
Thank you I’ve been trying to find transmission codes all over the place. My assumption is a bad sensor, i doubt it is actually getting too hot becasue it will not shift into 4th immediately when i start the car and will take about 5-10 min until it does.

I have a 96GC do you think the sensors are interchangeable? I know it is obd2 but maybe the internal sensors are the same.
 

· Registered
Joined
·
3,622 Posts
I have a 96GC do you think the sensors are interchangeable? I know it is obd2 but maybe the internal sensors are the same.
I believe that the 96 has the 4 pin sensor and the 95 has the 3 pin sensor, but I am not 100% sure what the crossover is. If you swap the entire sensor package and wire harness, they should interchange. Some companies sell the later sensor and solenoid as an kit with a new wire harness for just that reason. I think the later parts are better (?).
Camera lens Camera accessory Camera Digital camera Reflex camera
Automotive lighting Steering part Audio equipment Cable Wire


See the four pin vs three pin above.
 

· Registered
Joined
·
66 Posts
Discussion Starter · #9 ·
Alright thanks for all of the information guys. I was driving today and noticed that when i was going uphill around 35mph and i dropped the shifter into 2nd gear, this brought me to around 3k rpm. Idk if this changed anything, however after i did that it went back to normal shifting.

This makes me believe that this could be a clog in the cooling system or something(maybe).

I will see how it acts the next few times i drive especially when the weather starts cooling down. And after i will do a fluid and filter change, not that i think the transmission needs it for say but maybe when it got hot some clutch material clogged some of the passages in the tranny.

Either way if it doesnt get any better ill have to pull the pan off any way so might as well change the filter while I’m at it.

Also when I have the pan off what are some other things i can look at/replace to make it run a little better, I’ve heard that a common “upgrade” is to get a thicker 3-4 shift spring. Again thanks for all of the insight and i dont feel like i will just be throwing parts at the car and see which ones do the trick.
 

· Registered
Joined
·
3,622 Posts
Yes, if you are dropping the pan and swapping solenoids/sensors, might be a good idea to replace the 3-4 accumulator spring as it is almost certainly broken. It's cheap and available all over.

Would not hurt things to adjust the bands too.

Someone on here had an issue where an aftermarket cooler clogged up and caused issues. It was because the cooler had thin tubes with turbulators. The stock stuff seems better (as far as not getting clogged that is), but IMS if you still have the stock check valve they can stick and cause problems.
 

· Hears the voices
Joined
·
16,866 Posts
After it shifts into 4th after 5 minutes or so it shifts completely normal for the rest of the time it is running and even goes into overdrive.
4th gear is overdrive . . .
 

· Registered
Joined
·
66 Posts
Discussion Starter · #13 ·
Yes, if you are dropping the pan and swapping solenoids/sensors, might be a good idea to replace the 3-4 accumulator spring as it is almost certainly broken. It's cheap and available all over.

Would not hurt things to adjust the bands too.

Someone on here had an issue where an aftermarket cooler clogged up and caused issues. It was because the cooler had thin tubes with turbulators. The stock stuff seems better (as far as not getting clogged that is), but IMS if you still have the stock check valve they can stick and cause problems.
Okay thanks for all the info. Got a lot to tackle when i take the pan off. I do have a factory 95 transmission laying around in my garage that i was thinking about sending to a transmission shop so they can do a bench build on it.

I know one small problem but anting to do a full rebuild but it has been on my mind and i was planning on installing an aftermarket cooler in the process.

Anyway for now I’m just going to mess with the sensors, accumulator spring, and filter.

Where would the check valve be located? Somewhere in the cooling lines I’m sure but do you know which one and or how i can tell if it is malfunctioned. Thanks again for the info
 

· Registered
Joined
·
66 Posts
Discussion Starter · #14 ·
4th gear is overdrive . . .

I know it is a 4 speed with an OD unit. When shifting there if 4 solid gears and the over drive which seems o consist of one gear if thats what you can call it. I know it is 4th and OD becasue once i hit 30mph it goes into 4th and after 45mph it goes into OD. Dont know the exact difference between 4th and OD but i know there is a definite shift and rpm change at 45mph.
 

· Hears the voices
Joined
·
16,866 Posts
Ah, what you're calling OD there is the torque converter locking.
 

· Registered
Joined
·
66 Posts
Discussion Starter · #16 ·
Got cha i wasnt quite sure how the OD worked. I just know if i turn it off i run at like 2200rpm at 70 mph and with it on I’m more at 1700rpm.
 

· Registered
Joined
·
3,622 Posts
Where would the check valve be located? Somewhere in the cooling lines I’m sure but do you know which one and or how i can tell if it is malfunctioned. Thanks again for the info
Should be were the hard lines from the trans meet the rubber hoses coming from the radiator. My 93 was already missing it when I bought it so I have never actually seen it in person. There are some threads on it around.
 

· Premium Member
Two ZJ niners
Joined
·
11,933 Posts
I know it is a 4 speed with an OD unit. When shifting there if 4 solid gears and the over drive which seems o consist of one gear if thats what you can call it. I know it is 4th and OD becasue once i hit 30mph it goes into 4th and after 45mph it goes into OD. Dont know the exact difference between 4th and OD but i know there is a definite shift and rpm change at 45mph.
It's a 3-speed with an OD unit - and a lock-up torque converter. As was mentioned, the "shift" you feel when in OD is the TC lockup (rpms drop by about 200-250) after you reach around 45mph. With the OD disabled from the OD-off button, TC will lock up in 3rd gear.
 

· Registered
Joined
·
3,622 Posts
The temp sensor is in the 3 or 4 pin sensor (governor pressure and temp in one sensor). If your code 16 is because of a bad sensor then a new one should fix it.

The pics I posted are the solenoids and show the 3 and 4 pin connectors for the pressure sensor.
 
1 - 20 of 45 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top