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Discussion Starter · #1 ·
Newbie here but not to Jeeps.

Looking hard at 2 TJ Unlimited Rubicon. 1 with 6spd, one with 42RLE. I am new to the 4spd auto in this iteration and have the AX4 in my XJ. Both are low mile units and appear to be very clean, prices are close with no negotiations yet.

The 42RLE has been rebuilt "upgrading all the weak parts" and carries a 2 year warranty with 18 mo. left on the warranty.
Is that a thing - upgrading all the weak parts? And does that make it a much better transmission? I know the pro/con of manual vs. auto; they both have both. I'm used to auto, like it on the street and the trail, in a bit of rocks, etc. Haven't had a stick since my '75 CJ5.

I guess the question is: does the auto make it a deal breaker for some of you? Is it THAT bad?
I actually like the build of the automatic "LJ" a bit better than the stick, and it's a bit cleaner, but it has somewhat higher miles on it, albeit both have low miles for their age. The auto is '05, manual '06, both extremely clean, tummy tuck, etc, etc.
I'm trying to get answers to the gearset in each since both are running 35s. I'm hoping at least 4.88 but suspect both have the 4.11 stock Rubi gears. If I can make a decent deal and they are 4.11 I have no issue having 5.13 installed (pretty optimal for my use from the research I've done). For comparison, I run 4.56 on 33s in my XJ and like where the torque band is on the road and off. I understand the 42RLE is not the same trans. Step 1 if I buy the auto will be to install a large stand-alone trans cooler.. another question I've asked the owner of the automatic. Not a big deal since the trans was built 5 months ago so I could get a cooler done before heat takes it's toll.

I'd been considering selling the XJ but put a lot into it lately and over the years and had it on two trails yesterday for 2 recoveries, it was flawless. Apples and oranges comparison IMO. Spent last Sunday driving a buddy's LJ Rubicon on the trail and it really just feels more like a Jeep. So, if I can have both, why the hell not.

TIA for any insight.
 

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no, its not that bad of a transmission. note, it was the transmission used to win KOH every man challenge the first few years. does it have a super deep o/d and run hot, absolutely. if geared properly (5.38 for 35's) and cooled properly (passive cooler in the grill) it runs well. the 05 auto does have a chance of having a ECM issue where it causes hard shifts till the trans is warmed up and a CEL. wrangler fix seems to have a solid ECM that takes care of it. im not sure what weak parts could be upgraded, that sounds like salesman fluff
 

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It's a good transmission, mine has served me well save one solenoid pack I had to replace that required I drop the pan and valve body for. More important is what model year is the Unlimited? 2004 is fine, 05/06 can have some issues but they're not with the transmission itself.
 

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Discussion Starter · #5 ·
It's a good transmission, mine has served me well save one solenoid pack I had to replace that required I drop the pan and valve body for. More important is what model year is the Unlimited? 2004 is fine, 05/06 can have some issues but they're not with the transmission itself.
Expound on that please. Whatever it is, shouldn't it be with both TJ and TJU Rubicon?
 

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Any 05/06 TJ with the 42RLE, it doesn't matter if it's the TJ, TJU, Rubicon, or TJU Rubicon. The 05/06 PCM has problems with the 42RLE control circuit, it can literally implode. It has been described to me by a PCM repair company as looking like a .410 shell went off inside.
 

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Discussion Starter · #7 ·
no, its not that bad of a transmission. note, it was the transmission used to win KOH every man challenge the first few years. does it have a super deep o/d and run hot, absolutely. if geared properly (5.38 for 35's) and cooled properly (passive cooler in the grill) it runs well. the 05 auto does have a chance of having a ECM issue where it causes hard shifts till the trans is warmed up and a CEL. wrangler fix seems to have a solid ECM that takes care of it. im not sure what weak parts could be upgraded, that sounds like salesman fluff
Definitely would be going with stand alone cooler.

Yeah, I've been reading all I can find here and elsewhere about gear selection. And have been pondering the gears. I hesitate for 5.38 due to size of pinion and thinking 5.13 for a bit more 'strength'. All I have to compare is my XJ/4.0/AW4/4.56/33". I like that combo fine all around so wonder what the difference would be TJ vs. XJ as far as gearing and how the 4.0 or trans gearing might change that seat of the pants. Also, I live at 5500' and go higher when wheeling.

Visited with a guy from Idaho at the local car show today. He's running TJ Rubicon with 5.3 conversion. Nice rig but at a car show - tells me how it'll lift the L/F tire through 2nd.. big whoop - I wandered off. He commented that the TJ Rubicon was a good 5spd manual and the TJU/LJ was 6spd manual with issues. Didn't know that, or he's FOS. Enlighten me. He also didn't know the 42RLE had some issues.

Thanks for the responses gents.
 

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Discussion Starter · #8 ·
Definitely would be going with stand alone cooler.

Yeah, I've been reading all I can find here and elsewhere about gear selection. And have been pondering the gears. I hesitate for 5.38 due to size of pinion and thinking 5.13 for a bit more 'strength'. All I have to compare is my XJ/4.0/AW4/4.56/33". I like that combo fine all around so wonder what the difference would be TJ vs. XJ as far as gearing and how the 4.0 or trans gearing might change that seat of the pants. Also, I live at 5500' and go higher when wheeling.

Visited with a guy from Idaho at the local car show today. He's running TJ Rubicon with 5.3 conversion. Nice rig but at a car show - tells me how it'll lift the L/F tire through 2nd.. big whoop - I wandered off. He commented that the TJ Rubicon was a good 5spd manual and the TJU/LJ was 6spd manual with issues. Didn't know that, or he's FOS. Enlighten me. He also didn't know the 42RLE had some issues.

Thanks for the responses gents.
Not finding the Edit button so here goes:

All else being equal would you choose the manual 6spd over the 42RLE? Talking reliability, not driving characteristics.
 

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Yeah, I've been reading all I can find here and elsewhere about gear selection. And have been pondering the gears. I hesitate for 5.38 due to size of pinion and thinking 5.13 for a bit more 'strength'.
The pinion strength is the same between the 5.13 and 5.38, don't get mislead by anyone claiming anything else where the TJ gears are concerned. There are WAY too many of us running 5.38 gears, me included for years, without problem. 5.38 is a non-issue, strength-wise. Even 5.38 is very slightly undergeared for a TJ with 35" tires and 42RLE transmission. It's ok and good on the highway but I still wish it had another 150 or so RPMs when on the highway.

IMHO, after 3 years running the ratio even 5.38 is very slightly undergeared for the highway with 35" tires and the 42RLE. 5.13 would be even more slightly undergeared. Both are ok on the highway but 5.38 is better. Both are superb offroad.
 

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Not finding the Edit button so here goes:

All else being equal would you choose the manual 6spd over the 42RLE? Talking reliability, not driving characteristics.
Absolutely not. The 42RLE is a good transmission, it just needs its axles to be geared lower for it to make a superb highway and offroad combination.
 

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Discussion Starter · #11 ·
Absolutely not. The 42RLE is a good transmission, it just needs its axles to be geared lower for it to make a superb highway and offroad combination.
What would you consider ideal ratio with the 6spd? What cruise speed is everyone running. 75 seems pretty quick in any older jeep... or that's just me.
And what RPM do like on the highway? I did read here somewhere that the 4.0 likes 3k but that seems high to me. Currently I cruise 65 at about 2300 with 4.56/33/AW4. I wish I had 4.88 but the diffs came built this way.
 

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Discussion Starter · #12 · (Edited)
On the phone with a well known aftermarket outfit I'm told 4.88 with the 6spd if that's the way I go, and if I ever find out what's in it now. Needing a gear swap is not a deal breaker but maybe a negotiating point.
I have a buddy with 6sp Rubi and pretty sure 4.11 on 35s and we did fine crawling with 4:1 but I don't know about his highway performance. Maybe he needs a simple gear swap instead of the supercharger he's picking up this week.

I'm leaning toward the '06 with 6 spd, half the mileage, half the distance to look/drive/trailer home, and other goodies, and also take the PCM out of the equation. And I know - GL4, NOT GL5!

Thanks again.
 

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Probably no one cares about this issue but me, however the crux of any question comparing two components or systems is what is the actual failure rate and how large are the sample sizes. So often all we are doing in situations like this is offering personal opinion based on isolated examples from our own experience. How often do 42RLEs fail in comparison to manual models in for example 100 TJs in each group and then if there is a difference is it statistically significant?

Just my two cents
 

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Discussion Starter · #14 ·
Probably no one cares about this issue but me, however the crux of any question comparing two components or systems is what is the actual failure rate and how large are the sample sizes. So often all we are doing in situations like this is offering personal opinion based on isolated examples from our own experience. How often do 42RLEs fail in comparison to manual models in for example 100 TJs in each group and then if there is a difference is it statistically significant?

Just my two cents
Yup, I'm smelling what you're stepping in.

I've been on enough various forums for enough time to know all that going in with a question. I understand it comes down to the guy asking to make the final decision, but I like hearing views from folks who have BTDT with something that I'm just getting into - I wanna know too. I've built some nice stuff over the years with advice online, without ever meeting my advisors, and it's not too tough to sift through the BS if there is any. Although anecdotal, I don't dismiss opinions, especially when I initiate the conversation. In the end I'll likely end up choosing what my gut told me in the first place, but then I'll have something to base my decision upon and know why I made the choice.

FWIW the 2 guys who've jumped in to answer a question that's likely been asked a bazillion times on this forum have 7,000 and 50,000 posts. I think I'll shut up and learn. What will I do with the knowledge? See above.

Have fun.
 

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I have stock Rubicon gearing running 33x12.5x15 mud terrains. in 6th gear, 70 mph on the highway all day long at approx. 2750 RPM. I don't usually go 75+, but would be closer to 2900-3000 RPM at 75. Bigger tires would do better with a gear change, but I am happy with the stock 4.11 gearing and my 33's for my mix of local and highway driving. Not sluggish at all. Can still get out of its own way when needed.
 

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Discussion Starter · #17 ·
Took the plunge on the 6spd Rubicon LJ. I'll drive it with 4.10/35/12.5/15 for a year or so and have a better seat of the pants feel for what I need. I have no doubt the 241/LJ will be a welcome change from the 231/XJ/33/4.56/AW4 for low end trail work. The onroad is what I'll be interested to see. I'm fine at 70mph but I'll have to see how it does with the multiple elevation changes on I80 in Nevada.

Thanks for the replies.
 

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I think 5th gear will be your new friend in Nevada on the highways. It is pretty responsive from 50-65 MPH. You should still be able to maintain RPMs decently on highways with elevation changes. Flats and mild grades, you could probably do 6th to maintain 65+ MPH, but the hillier sections would probably require 5th. Once there, I don't think you'd have to downshift to 4th too much if at all. 5th is really pretty torque-y and loves the 2750-3000 RPM range.

We don't have too many real mountains in Massachusetts (compared to Nevada and out west), so interstates at 65-70+ for me are 6th gear all the time, with occasional downshift to 5th on the "big hills".

Note: If the OPDA is original or unknown, change it out for a new Crown OPDA. DO NOT throw the old sensor out! Be sure to use the original sensor in the new OPDA. Keep the sensor that came with the new OPDA with the old OPDA in a box on a shelf, as an emergency spare. If something happens to either the sensor or the OPDA, you can pop the spare back in to stay on the road while waiting for replacements to arrive.
 

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Discussion Starter · #19 ·
I think 5th gear will be your new friend in Nevada on the highways. It is pretty responsive from 50-65 MPH. You should still be able to maintain RPMs decently on highways with elevation changes. Flats and mild grades, you could probably do 6th to maintain 65+ MPH, but the hillier sections would probably require 5th. Once there, I don't think you'd have to downshift to 4th too much if at all. 5th is really pretty torque-y and loves the 2750-3000 RPM range.

We don't have too many real mountains in Massachusetts (compared to Nevada and out west), so interstates at 65-70+ for me are 6th gear all the time, with occasional downshift to 5th on the "big hills".

Note: If the OPDA is original or unknown, change it out for a new Crown OPDA. DO NOT throw the old sensor out! Be sure to use the original sensor in the new OPDA. Keep the sensor that came with the new OPDA with the old OPDA in a box on a shelf, as an emergency spare. If something happens to either the sensor or the OPDA, you can pop the spare back in to stay on the road while waiting for replacements to arrive.
Good stuff, thank you. Ya, I'll whirl it around awhile as is and kind of like keeping the original diffs intact.
"loves the 2750-3000 RPM range." I've had my 4.0L XJ for years but never drove it over 65 until yesterday at 70/2700-ish. Yup, it did seem to purr like I hadn't heard or felt before. I guess it doesn't matter the gear if the rpm is where the engine is happy. I'd read the same thing here in another post.

OPDA? Had to look it up and found a pretty good YouTube video.


I don't even know if my '99 4.0 has an OPDA but I carry a MOPAR CPS on the trail so I'll do the same with LJ
I'll be getting this week with 29k mi. so I'm certain the OPDA is original, but I'll take your advice and put Crown OPDA on my to-do list.

Outstanding and much appreciated!
 

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Good stuff, thank you. Ya, I'll whirl it around awhile as is and kind of like keeping the original diffs intact.
"loves the 2750-3000 RPM range." I've had my 4.0L XJ for years but never drove it over 65 until yesterday at 70/2700-ish. Yup, it did seem to purr like I hadn't heard or felt before. I guess it doesn't matter the gear if the rpm is where the engine is happy. I'd read the same thing here in another post.

OPDA? Had to look it up and found a pretty good YouTube video.


I don't even know if my '99 4.0 has an OPDA but I carry a MOPAR CPS on the trail so I'll do the same with LJ
I'll be getting this week with 29k mi. so I'm certain the OPDA is original, but I'll take your advice and put Crown OPDA on my to-do list.

Outstanding and much appreciated!
99 does not have an OPDA. OPDA is only 05-06 models.
 
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