42RLE Transmission Slipping

FamilyFunWagon

FamilyFunWagon

TJ Enthusiast
Original poster
Joined
Mar 18, 2020
Messages
199
Location
Southern California
Hello All,

I have a 2004 Rubicon Automatic 42rle. It has a derale transmission cooler on it.

I was driving and I noticed the transmission "slip" right at 2400 rpm. It was brief and if I wasn't paying attention I would have missed it. Anyway, I believe it is slipping when shifting from 2nd to 3rd. You can see the rpm's jump. .

I also noticed my transmission cooler was running when just going from my house to my parents (maybe 3.5 miles away). Which makes me think it is running hot. When driving I can feel the heat on my leg from the transmission. This may be normal but I don't know.

I checked the fluid with it in neutral and it seems to be in the hot.

The transmission was serviced by jeep and the rear main seal was changed about 1200 miles before I bought it. I have the service records.

I rarely use my jeep.. it sits in the garage and gets used maybe once a month. I have owned for a year and put maybe 2500-3000 miles on it.

Should I drop the fluid and replace the filter?

Will this help?

Or should I have it serviced?

I have a video, I hope it will allow it to post.
 
Are you sure all your cooler lines are in good condition and not kinked? A kinked line could cause some weird stuff to happen. Personally I'd find a good transmission shop that knows exactly what a 42RLE is and let them have at it with a good scanner. The clutch volume index will tell you if one of the clutches on the way out. Without a check engine light it is unlikely there is anything seriously wrong but if you are worried it probably is a good idea to get it checked. New fluid is unlikely to fix a problem in the transmission but you should be changing the filter on schedule. Changing the filter is the service for that transmission, anything else is really a rebuild or repair. There are no adjustments or simple tune-ups a generic service place can do.
 
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First things first, check its ATF level. While the engine is running and the Jeep is parked on level ground, check its ATF level. It should be all the way up to the top of the full mark. If it's low, insert a small funnel into the dipstick tube and add enough ATF+4 (only!!) to bring it to the full mark while the engine is running.

The engine MUST BE RUNNING while you check the ATF level, otherwise the dipstick will show it is fuller than it really is. And if it's low, make sure the ATF you add says "ATF+4" in big letters on the front of the bottle. No other ATF is correct for any of our Jeep automatic transmissions.
 
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Jerry Bransford said:
First things first, check its ATF level. While the engine is running and the Jeep is parked on level ground, check its ATF level. It should be all the way up to the top of the full mark. If it's low, insert a small funnel into the dipstick tube and add enough ATF+4 (only!!) to bring it to the full mark while the engine is running.

The engine MUST BE RUNNING while you check the ATF level, otherwise the dipstick will show it is fuller than it really is. And if it's low, make sure the ATF you add says "ATF+4" in big letters on the front of the bottle. No other ATF is correct for any of our Jeep automatic transmissions.
Click to expand...
I checked it on level ground with it running and it is to the top full mark. The rear main seal has a slight leak.

I am wondering if I should have bled the transmission fluid when I put the cooler on there. If that is even possible.
 
pagrey said:
Are you sure all your cooler lines are in good condition and not kinked? A kinked line could cause some weird stuff to happen. Personally I'd find a good transmission shop that knows exactly what a 42RLE is and let them have at it with a good scanner. The clutch volume index will tell you if one of the clutches on the way out. Without a check engine light it is unlikely there is anything seriously wrong but if you are worried it probably is a good idea to get it checked. New fluid is unlikely to fix a problem in the transmission but you should be changing the filter on schedule. Changing the filter is the service for that transmission, anything else is really a rebuild or repair. There are no adjustments or simple tune-ups a generic service place can do
Click to expand...

pagrey said:
Are you sure all your cooler lines are in good condition and not kinked? A kinked line could cause some weird stuff to happen. Personally I'd find a good transmission shop that knows exactly what a 42RLE is and let them have at it with a good scanner. The clutch volume index will tell you if one of the clutches on the way out. Without a check engine light it is unlikely there is anything seriously wrong but if you are worried it probably is a good idea to get it checked. New fluid is unlikely to fix a problem in the transmission but you should be changing the filter on schedule. Changing the filter is the service for that transmission, anything else is really a rebuild or repair. There are no adjustments or simple tune-ups a generic service place can do.
Click to expand...
Do you happen to know how I might go about finding a transmission shop that would be capable of running these test?
 
FamilyFunWagon said:
Do you happen to know how I might go about finding a transmission shop that would be capable of running these test?
Click to expand...
I would imagine IF you can locate a shop that not only services, but actually rebuilds the transmission; that shop should have the tools to accomplish these tests....
 
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FamilyFunWagon said:
I checked it on level ground with it running and it is to the top full mark. The rear main seal has a slight leak.

I am wondering if I should have bled the transmission fluid when I put the cooler on there. If that is even possible.
Click to expand...
No worries on bleeding the ATF lines after installing the cooler. When you say rear main seal is leaking, you're talking about at the rear of the engine right? If so, are you running a synthetic engine oil? If so, changing it to a High Mileage CONVENTIONAL engine oil like a 10W-30 will very likely cure the leaky rear main seal.
 
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Jerry Bransford said:
No worries on bleeding the ATF lines after installing the cooler. When you say rear main seal is leaking, you're talking about at the rear of the engine right? If so, are you running a synthetic engine oil? If so, changing it to a High Mileage CONVENTIONAL engine oil like a 10W-30 will very likely cure the leaky rear main seal.
Click to expand...
Hello Jerry,

Yes I am running synthetic Castrol. Thank you for the advice. Should I change the oil asap or should I Wait until my next change. Again, thank you.
 
Jerry Bransford said:
No worries on bleeding the ATF lines after installing the cooler. When you say rear main seal is leaking, you're talking about at the rear of the engine right? If so, are you running a synthetic engine oil? If so, changing it to a High Mileage CONVENTIONAL engine oil like a 10W-30 will very likely cure the leaky rear main seal.
Click to expand...
Would you recommend changing all 12 quarts by disconnecting the return line? I was reading a write up on this, but I have also heard this is not recommended. I have also read that the 42rle will nead to "re-learn" after changing the fluid. When I added the transmission cooler and added fluid, could this have caused the slipping?

Or am I just overthinking this?

I just think it is weird that the issue didn't start until I added a transmission cooler.
 
I'd start with simple stuff first. If the electrical connectors are connected, the fluid level checks out, and the lines aren't kinked, you could temporarily remove the cooler by bypassing it. Since that's the only thing you've done recently, it makes sense to begin there.

Given you will likely make a mess with fluid draining during the temporary splice, I'd probably drop the pan first. This will allow you to check the pan magnet for metal debris and check the transmission filter. There should be an o-ring when removing the filter. Make sure that's in place. If the filter needs replacing, use a Mopar one. Also, use only ATF+4 and install a pan with a drain. When removing and installing the pan, it's important to not over tighten the bolts. FWIW, the correct way to keep an eye on the transmission temperature is to install a gauge. If you're not comfortable with any of this, take it to a shop and have them look at it.

https://www.amazon.com/dp/B00F6E49UW/?tag=wranglerorg-20
https://www.amazon.com/dp/B00Z7O4OVA/?tag=wranglerorg-20
 
FamilyFunWagon said:
Would you recommend changing all 12 quarts by disconnecting the return line? I was reading a write up on this, but I have also heard this is not recommended. I have also read that the 42rle will need to "re-learn" after changing the fluid. When I added the transmission cooler and added fluid, could this have caused the slipping?

Or am I just overthinking this?

I just think it is weird that the issue didn't start until I added a transmission cooler.
Click to expand...
Pay no attention to the rumors, no the transmission does not need to relearn anything after changing the ATF. And a properly installed transmission cooler causes zero problems. There's already one cooler installed by the factory, you're just adding a second in series with it. I installed and am running the same cooler myself.

And if your existing ATF level is all the way to the full line when the engine is running, and it's clear/red and not burnt smelling or appearing, it's very likely fine and not in need of being changed.
 
My own experience included noticing it slipping, and/or running hot on any type of incline. After a few months of intermittent symptoms, it started throwing codes and even went into limp mode. I believe the issue was the torque converter, but I went ahead and had the whole thing rebuilt. That was at 130k miles.
 
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Well I changed the fluid and filter. It was pretty clean fluid. Anyways, it is still slipping. I think I am going to take it to westminister transmission and have them give it a look.
 

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