42RLE no 3rd or 4th gear

Jeffh555

Red Skull
Joined
May 21, 2020
Messages
710
Loc
Scotts Valley, CA
2011 JKUR, 3.8L, 42RLE, ~80k miles, SD60/10.5, 5.38 gears, 40s, I bought it from 2big bronco but he didn’t build it.

Earlier this year it decided to stop shifting into 3rd or 4th gear. It will run through 1st and 2nd no problem but when it goes to grab 3rd, the motor just spins up as though it’s in neutral.

Is my tranny blown, or is it just confused?

More details:

If it does this for too long, it’ll go into limp mode and be stuck in 2nd gear.

I discovered this 2 days before a Sand Hollow trip, flushed the fluid (which looked fine) and put a new filter in it. I think that temporarily fixed the problem, but I may have rushed the test drive.

Once I got to Sand Hollow, it was back in limp mode. I discovered I could reset the codes then keep it in 1st and 2nd and I wheeled it all week.

I was convinced that it was the shift solenoids, so I replaced them, didn’t change the issue.

I have the following “permanent” codes:

P0882 TCM Power Input Low

P0733 Gear Ratio Error in 3rd

P0734 Gear Ratio Error in 4th

I’ve also seen the follow code while trying to test drive and figure out what’s going on.

P1790 Fault Immediately After Shift

After I typed all this out, it just occurred to me that, it worked fine at Fordyce in the fall (no river crossing, water was too high) and then it sat all winter, and the battery probably died. I remember when 2BB sold it to me, he gave me a Bluetooth OBD dongle and told me the previous owner told him that if the computer lost calibration for tire size/gearing, it wouldn’t run right. I’ll try adjusting the tire size/gearing in Jscan tonight and see if that changes anything.
 
Put a new battery in it because it wasn’t taking a charge.

Changed the gear ratio and tire size. Still makes zero effort to engage 3rd gear.

I now have more codes. Some may be because of the low battery, we’ll see after I put some hours on it.

It still seems to hold 1st and 2nd fine, I’m putting it on the trailer and going wheeling tomorrow.
 

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It's been a few months, still don't have a working JK, but have tried some things and learned some things, and have even more questions.

PCM went to Wrangler Fix, they put it in their 2011 JK, it worked fine, put it back in my JK, same issues.

Did some reading and it seems that my Overdrive Clutch isn't engaging. It's called the overdrive clutch, but it engages in 3rd and 4th gear.

Used the OBD JScan app to pull the CVI (Clutch Volume Index) data, I forgot to screenshot the numbers, but they were all in spec. This makes me think the overdrive clutch isn't worn out, but maybe I'm interpreting this wrong.

Completed Hydraulic Pressure tests by hooking a pressure guage to the pressure taps on the side of the transmission with the rear end up on jack stands.
Underdrive clutch had a steady 130psi in 2nd gear. Spec is 110-145 psi.
Overdrive clutch initially goes to 90psi in 3rd gear, but then falls to just over 60psi after about a second and is bouncing around a lot. Spec is 75-95 psi. If I find just the right throttle position I can get it to be stable at ~62psi.

The JK 42RLE has Variable Line Pressure (VLP), where the TJ/LJ 42RLE doesn't. As far as I can tell, VLP is supposed to reduce line pressure once the gear is engaged to improve fuel economy (reducing the pump load). This is a JKU on 40s, DGAF about highway fuel mileage. I need to look into if this system is functioning correctly, if there's any way to test it, and if I can disable it.

I wish I knew a good transmission tech that I could run this by and they could tell me what's going on.

I don't want to replace a transmission that's otherwise good. More importantly, I don't want to replace a transmission and still have the same problem.
 
I know nothing about theses trannies, but that bouncing around od clutch pressure in 3rd seems like the VLP is doing something strange. Is that how it is supposed to function?
 
I also know nothing about these transmissions.

I’m too stubborn to spend $2500+ on a new transmission without knowing the problem. I’d happily tow the Jeep an hour and pay a shop 2 hours labor to diagnose it, but I’m confident most shops would just tell me it needs a new transmission.

I found this article about VLP, and it seems like the pressure is low and I should do some more testing.

First and second gears run around 135 psi (figures 1 and 2). For third and fourth pressure is dropped to around 85 psi (figures 3 and 4). Once lockup is fully applied, line pressure is commanded to drop even lower (Figure 5).
Click to expand...

www.transmissiondigest.com

The Variable Line Pressure Solenoid - Transmission Digest

The 41TES and the 42RLE-VLPS are known to produce a “Line Pressure to High” code P0869 due to defective TCM/PCM’s immediately after a 2-3 shift.
www.transmissiondigest.com www.transmissiondigest.com
 
So that article says you should be seeing 85 in 3rd where you've got 60 and fluttering. Have you priced a VLP solenoid to try swapping for ****s and giggles?
 
Have you put a gauge with long hose on overdrive clutch pack’s test port to see what pressure it’s at when going into 3rd gear at speed? It’s what I’ll do as this is pointing at this clutch pack to be bad.
 
Found another article about VLP, and it seems like it would throw a code for high or low VLP. It makes me wonder if the sensor is giving a bad signal. It looks like I can read both desired line pressure and actual line pressure in JScan.

www.fenderbender.com

The VLPS

Chrysler introduced a Variable Line Pressure Solenoid to the existing 41TE (A604) and 42RLE transmission as early as 2007. The addition of this solenoid includes the use of a ...
www.fenderbender.com www.fenderbender.com

It's $180+shipping for a new solenoid, sensor, and harness. They're located in the top of the valve body, so if I'm pretty sure that's it, I'll swap it all.

Trans Variable Force Solenoid Sensor - Mopar (5078911AA) $60.77

Trans Pressure Transducer Sensor - Mopar (5078336AC) $77.53

Variable Line Pressure Harness - Mopar (5078341AA-MOPAR) $42.88
 
TrailTamer said:
Have you put a gauge with long hose on overdrive clutch pack’s test port to see what pressure it’s at when going into 3rd gear at speed? It’s what I’ll do as this is pointing at this clutch pack to be bad.
Click to expand...
Yes, I have the gauge hose routed through the shift cable hole in the the floor. When it shifts into 3rd, it spikes to 90psi for a second or less, then falls to 60. Does this on jack stands or on the road.

Does this seem to be what a bad clutch pack would do?

I'm far from an expert, but I'd think a bad clutch pack would take the pressure, but slip anyway.
 
Tire speed slow down or continue to speed up after shifting into 3rd on jack stands? It might not slip with light/no load with tires off ground (or tires taken off entirely)?
 
Last edited:
On jack stands when it shifts into 3rd it's really hard to hold a steady wheel speed or rpm, it seems like it will either grab, bog down, and then shift back into 2nd, or spin through 3rd. I'll try again tonight and try to pay more attention to it.

I did think of the fact that I'm there's no load, so I tried dragging the brakes, it made it easier to hold speed/rpm, but didn't cause pressure to go up.

I'll also go out and try these things on the road.
 
I have rebuilt a few autos, never was into a 42rle. Done a good bit of gm 4l60 stuff and 47rh.

If it were me , id would get a good used junkyard transmission and throw that in to get going. Then I would rebuild the old one with whatever valve body/shift kit is available to get the shifts firm and line pressure all the way up. I would be putting good odds that the clutch assembly for 3rd 4th is smoked.

That clutch being smoked is also not the cause but a symptom of the failure which is erratic/low line pressure to the clutch pack.

I have had good luck getting the 3/4 clutch to hold up in a 700r4 with an abusive right foot. And that is the single biggest failure point of the 700/4l60 gm trans family. The root issue is always low line pressure to the clutch, whether its a teflon seal, internal valve body leak, leak in the drum. Whatever it is, any fluid leak going to the clutch will cause it to fail.
 
Alexis700 said:
I have rebuilt a few autos, never was into a 42rle. Done a good bit of gm 4l60 stuff and 47rh.

If it were me , id would get a good used junkyard transmission and throw that in to get going. Then I would rebuild the old one with whatever valve body/shift kit is available to get the shifts firm and line pressure all the way up. I would be putting good odds that the clutch assembly for 3rd 4th is smoked.

That clutch being smoked is also not the cause but a symptom of the failure which is erratic/low line pressure to the clutch pack.

I have had good luck getting the 3/4 clutch to hold up in a 700r4 with an abusive right foot. And that is the single biggest failure point of the 700/4l60 gm trans family. The root issue is always low line pressure to the clutch, whether its a teflon seal, internal valve body leak, leak in the drum. Whatever it is, any fluid leak going to the clutch will cause it to fail.
Click to expand...
Thanks. I'm leaning towards rebuilding it myself, and having someone tell me I'm not a complete idiot is helpful.

Once I'm semi-confident that I've exhausted my troubleshooting in the vehicle, I'll pull the trans and rebuild it myself.

It's effectively a dedicated wheeler, and I'm not going to KOH this year, so I have about 3 months until my wheeling season starts. Around here Jeep parts are expensive, a junkyard transmission is going to cost me $1600+.
 
That pretty dang expensive. I haven't done anything with a 42rle , so dont have any advice to that particular transmission.

I dont know if mopar still did it for your year jeep , but for the 47rh transmission I am building I got a used factory dodge service manual for the truck that transmission came in. The factory service manual has way better information and drawings for rebuilding than the ATSG book. Dimensions for every part that can be checked, very detailed.

The ATSG books are affordable and decent , you can get it done with just that. I used to be afraid to dig into them, but they really arent that bad. Just some clutch packs and planetary gears , with hydraulics running the clutches.
 
I overhauled 47re in my truck and a 46re in a Ram 1500 we flipped. They’re not too bad.

I’d like to recommend to get yourself a parts washer, review repair manual for tools you may need and plan a weekend to get the trans torn down and reassembled. It’s to keep your mind fresh on how it came apart for reassembly and to prevent contamination or losing things from sitting until the next time you get back to it. Get yourself couple of folding tables if necessary to have more work space for keep things organized & clean for easy reassembly.





Slight thread derail;

I recently learned, after looking into this trans model because of this thread, interesting on how this 42rle is a “modified” 42re. It’s essentially a transaxle 42LE from caravan minivan but with chain and diff removed and a false overdrive tailhousing with stub shaft bridging between trans’s actual output to t-case input.

This explains on how AA comes up with a drop-in doubler without losing the overdrive gear because it’s essentially take in place of the false tailhousing.

advanceadapters.com

RUBICRAWLER JK W/HD T/C CABLE 2007-2011

RUBICRAWLER JEEP JK W/ Heavy Duty Deluxe TWINSTICK SHIFTER/ ALUMINUM KNOBS & CONTROL MODULE
advanceadapters.com advanceadapters.com
1737225822289.png


Why Chrysler did not put a little more effort into this 42rle to have the t-case to bolt directly to the main case to gain to much needed/desired rear driveshaft length on 2 door wranglers is beyond me. But the drop in doubler is :smokin:
 
I thought at first the 42rle was like the 46re which is a just a 3 speed tf999 from the 70s with an overdrive scabbed on the back and electronics jammed in. Thanks for that explanation, its got nothing in common with the ones I work on.

But yeah thats why I didnt give any specific advice, because my mopar transmission knowledge is for the tf727 based 4 speeds, 47rh/re. Same principles apply , good service manual, keep organized, parts washer, be meticulous and it will work out. I have built all my special tools , except bushing drivers but those were fairly cheap. Also spend some money on quality snap ring pliers, should cut down on the cuss words some. :laughing:
 
Last night I used JScan to monitor the computer’s desired line pressure vs computer actual line pressure vs the pressure tap at the overdrive clutch. They were all effectively the same. I didn’t road test it, but I did it with both the rear wheels spinning freely, and dragging the brakes.

This tells me that the trans is applying pressure to the overdrive clutch as intended, and it just isn’t holding.

I feel like I’m out of things to test with the trans in the Jeep and it’s time to set up a trans rebuild space.

TrailTamer suggested I pick up a ATSG manual, which seems worth it for $35. When I was on their website I noticed they have a service when I can have a technician call me. $75 per case, 10 calls within 30 days.

Pay-Per-Case - ATSG

* ATSG is a technical support service specifically for the Automatic Transmission Industry. We offer a Technical Hotline, Books, Software, Bulletins, Wiring Diagrams, Seminars, and Technical Courses to the Automatic Transmission Professional.
atsg.com atsg.com
 
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