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Unread 07-19-2010, 08:48 PM   #1
cragrat
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rubicon with auto trans questions

thinking about trading my jeep for an 06 rubicon. i have a few questions. i thought all rubicons had an sye and longer driveshaft. this one is an auto trans is that the difference? this thing has at least an inch tc drop. next, part of the reason for the trade is because i also have always wanted to run 35's. what gears are ya'll running with 35 inch tires. 3rd has anybody always driven manuals a got an auto trans? howd the transition work out for you? do i still need to upgrade the brakes for 35's? thanks.

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Unread 07-19-2010, 09:00 PM   #2
gremlinsteve
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what kinda jeep are you trading in for the rubi?

i drive automatics. thrs a reason for this. to each there own but i have never looked back.

steve
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Unread 07-19-2010, 09:01 PM   #3
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Having had both in the past, I'll stick with automatics from here on out!
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Unread 07-19-2010, 09:15 PM   #4
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Quote:
Originally Posted by cragrat View Post
thinking about trading my jeep for an 06 rubicon. i have a few questions.
See Below
Quote:
Originally Posted by cragrat View Post
i thought all rubicons had an sye and longer driveshaft.
NO. Rubicons have a FIXED FLANGE. They don't have a Slip Yoke to Eliminate. They still have SINGLE CARDAN rear driveshafts from the factory.

Read: http://www.jeepforum.com/forum/f9/wh...nt-one-854790/

Quote:
Originally Posted by cragrat View Post
this one is an auto trans is that the difference?
I hate the 42RLE auto. I've driven it for over 68k miles, and I think it should never have been installed behind a 4.0L. IMHO, they aren't reliable, they run very hot (every other 42RLE equipped Jeep got a factory trans cooler) and they seem to die an early death. mine died under warranty.

and even if you like the 42RLE, its grossly undergeared. It needs 4.56s with 31s to equal the 6-speed. 4.88s or 5.13s for 33s, and 5.89s for 35s.

i say stick with the NV3550 5-speed or the NSG370 6-speed, much better transmissions, with FAR better gearing.

Quote:
Originally Posted by cragrat View Post
this thing has at least an inch tc drop. next, part of the reason for the trade is because i also have always wanted to run 35's. what gears are ya'll running with 35 inch tires. 3rd has anybody always driven manuals a got an auto trans? howd the transition work out for you? do i still need to upgrade the brakes for 35's? thanks.
the 42RLE needs 5.89s to turn 35s reasonably, with 5.13s as a bare minimum. 5.89s requires new lockers in the Rubi D44s.

and yes you need to upgrade the brakes for 35s.
http://www.jeepforum.com/forum/f9/i-...-my-tj-751873/
http://www.jeepforum.com/forum/f9/tj...embers-722109/
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Unread 07-20-2010, 07:01 AM   #5
Zen
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What he said...

I do like having an automatic when offroad. I do a lot of rock crawiling and I have more controll resulting in much more precise lines and more capability than my buddy with his 2005 LJ Rubicon. Our Jeeps are identical down to the same lift manufacturer except he has the 6 speed. His is much more fun to drive on the road, which let's face it the Jeeps are on the road much more than they are off. I change my tranny fluid every 20K or so miles because when it gets old I start to notice a decrease in performance. My LJ has about 87K miles and the tranny is on its way out...
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Unread 07-20-2010, 09:45 AM   #6
Unlimited04
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I do like having an automatic when offroad. I do a lot of rock crawiling and I have more controll resulting in much more precise lines and more capability ..
I agree. I love the 42RLE off-road, and the high OD lets you drive 15-20mph in 4-low in between technical areas. But the 42RLE just sucks something fierce on the highway and street. Unforunately, most of us have to drive to the trail, DD the Jeep, etc. I see probably 97% street...and unless you trailer your Jeep to the trail, then you're the same way.
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Unread 07-20-2010, 09:48 AM   #7
Jerry Bransford
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Quote:
Originally Posted by Unlimited04 View Post
every other 42RLE equipped Jeep got a factory trans cooler) and they seem to die an early death.
Not sure what you're saying there but all Jeep automatics have an external automatic transmission cooler including the 42RLE and the 32RH it replaced. And when the axles have been regeared to a more appropriate lower ratio, the 42RLE is fine on the highway. Its overdrive ratio is just so steep that it needs a lower axle ratio to raise the engine rpms up to where the engine runs better.

If I was buying another Rubicon as I did a few months ago, I'd go with the automatic every time.
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Unread 07-20-2010, 10:29 AM   #8
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Originally Posted by Jerry Bransford View Post
Not sure what you're saying there but all Jeep automatics have an external automatic transmission cooler including the 42RLE and the 32RH it replaced. And when the axles have been regeared to a more appropriate lower ratio, the 42RLE is fine on the highway. Its overdrive ratio is just so steep that it needs a lower axle ratio to raise the engine rpms up to where the engine runs better.

If I was buying another Rubicon as I did a few months ago, I'd go with the automatic every time.
Jerry, install a trans temp gauge on your 42RLE and use a IR Temp meter to read the temp of the tranny housing and pan, even the extension housing which holds nothing but fluid. what you're calling an "external tranny cooler", the radiator pass through, has the 42RLE's return line temp at 200-240 F after long drives and hot days. and the lines pass less than 1/2" from both mini-cats running at 500-600+ F (external heat shield temp). I don't consider it a cooler at all...more like a warmer. KJ's came with a nice 42RLE cooler, about the size of the one I'm going to install on my LJ.

Regearing helps for sure, but it still shifts like crap. with 4.88s and 33s, it locks up in OD at ~37mph. like i said, it came undergeared from the factory (i have factory ratio on right now, and it sucks balls). With 30.5s and 3.73s, I can't maintain 60-75mph on any of the major highways around Denver. It routinely needs 3rd gear to climb the simplest of hills. Been like that since 30s and bone stock configuration...in fact, driving across Nebraska where the average speed is 80-85mph, I had to draft semi-trucks because the headwind required 3rd gear & 3500+ rpms. It wouldn't maintain 80mph in OD without a semi-truck breaking wind - at roughly sea level.

Now, if I am in OD between 60-75mph (cruise on), it runs full throttle to maintain speed. Even worse, with 3.73s and 33s, it needs 2nd and 3rd to maintain 60mph around 5300 ft elevation highways.

From the factory, it should have come with ~4.27ish gears for 29s/30s and 4.56 for 31s.


Thats my Jeep. 30s, 3.73s climbing I-70. 4500rpms required to maintain 55-60mph, speed limit is 65mph. I have to drop to 40-45mph so the engine doesn't scream at redline. Someone on this forum, a friend of mine and well respected member on here, blew his valvetrain apart, under warranty, trying to turn 4.88s and 37s up this same hill with the 42RLE.

For reference, AX15, NV3550 and NSG370 equipped TJ's climb this no problem at 60-70mph around 3000rpms. 4-door JK's on 35s with the 6-speed do it at 3200rpms. I tried to follow a nice lifted 2.8L diesel KJ one day. I couldn't even keep up. first hill he blew my Jeep out of the water and maintained 70mph where I had the pedal to the floor turning 4500rpms at 55mph in 2nd. I caught him on the downhill side by going 80mph, next hill...same thing. I was amazed. Also, my friend's XJ with 4.0L/AW4, 3.55s and 30s can run circles around me. Literally, he passes for fun climbing these hills. Mine requires 2nd gear when his is in OD or 3rd. and he's technically "undergeared" too....he can hear my 42RLE kick into 2nd...he comments on the CB radio. again...this isn't hot rodding or passing, thats just trying to maintain speed.

It ain't just me, or the TJ's...the JK's have the same problems.
http://www.jeepforum.com/forum/f96/w...-video-964113/

Last edited by Unlimited04; 07-20-2010 at 10:48 AM..
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Unread 07-20-2010, 10:36 AM   #9
gremlinsteve
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my auto has no issue holding 2100 rpm and 75 mph all day. i do not have the mountains to deal with tho. that i70 stretch is one mean grade isnt it?

i do feel i need to move up to the 456 gearing tho. and mine does not have a trans temp gauge attached to it.

steve
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Unread 07-20-2010, 06:50 PM   #10
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Unlimited- Have had this same problem many times in the mountains of VT. I have just come to accept that I cannot maintain 65-70MPH on a grade. I will say I think the Rubi version which I have does a little bit better on 4.11's. So other than crappy shifts, running hot, and dieing on me after 120,000 miles I am happy with this transmission . I will say I recently installed another external cooler in front of my rad and a autometer trans temp gauge, and I have been pleased with the results. I am now keeping the trans temps under 20o on most hot days.
Brian
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Unread 07-20-2010, 07:37 PM   #11
viperbluelx
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Quote:
Originally Posted by Unlimited04 View Post
See Below

NO. Rubicons have a FIXED FLANGE. They don't have a Slip Yoke to Eliminate. They still have SINGLE CARDAN rear driveshafts from the factory.

Read: http://www.jeepforum.com/forum/f9/wh...nt-one-854790/


I hate the 42RLE auto. I've driven it for over 68k miles, and I think it should never have been installed behind a 4.0L. IMHO, they aren't reliable, they run very hot (every other 42RLE equipped Jeep got a factory trans cooler) and they seem to die an early death. mine died under warranty.

and even if you like the 42RLE, its grossly undergeared. It needs 4.56s with 31s to equal the 6-speed. 4.88s or 5.13s for 33s, and 5.89s for 35s.

i say stick with the NV3550 5-speed or the NSG370 6-speed, much better transmissions, with FAR better gearing.


the 42RLE needs 5.89s to turn 35s reasonably, with 5.13s as a bare minimum. 5.89s requires new lockers in the Rubi D44s.

and yes you need to upgrade the brakes for 35s.
http://www.jeepforum.com/forum/f9/i-...-my-tj-751873/
http://www.jeepforum.com/forum/f9/tj...embers-722109/

My brothers 04 LJ has 27K miles and now goes into limp mode (locked in 2nd gear) after a few miles of driving. He's hoping it's just a solenoid pack in the valve body, we'll see. He's running 35's and stock 3.73 gears and it does fine around town and on the trails but he has to run with the OD on the interstate to maintain 70mph.
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Unread 07-20-2010, 07:51 PM   #12
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IDK... I don't seem to have the problems that U04 has had with his 42RLE. I have now had two. They have been the smoothest shifting auto I have driven, and that beats out my friend's Mercedes C300 Sport. The torque converter makes the 2.71 Low range nice, but with the 4:1 low of the Rubi I can't believe how amazing that is. Now need for the skinny pedal with rocks. It isn't so bad on the highway when geared right. I am geared a little too steep with 31"s and 4.10, but it isn't THAT bad. I got a consistent 24mpg in my last one with 28.5" wuss rubbers and 3.73 because of the gearing. You will want to go straight for 5.13 even if you are riding on 31"s for a short time.
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Unread 07-20-2010, 07:52 PM   #13
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I have 35's and stock Rubi gearing (4.10) no problems, It's no 'vette but I'm happy. Throws hi range roosts in the dirt and crawls great in lo. I have two temp gauges one in and one out, never gets to 200* on the street, when I flog her off road it gets near that.
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Unread 07-20-2010, 08:52 PM   #14
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Got an auto Rubi with 33's and stock gearing and have put over 50k miles on her with no issues. Run it in town with the OD switched off and it shifts fine and has appropriate power through the gear cycle. Use the OD for extended highway travel only.

Night and day difference operating with the OD off around town.
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Unread 07-20-2010, 08:58 PM   #15
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My Rubi used to do 75 all day long. Was my moms DD(about 75 miles a day) on 33s with 4.10 gears. Was an Auto too. I reccomend the auto for rock crawling and most off road.

I only got the 5 speed because I am just learning to drive and wanted to learn on a stick. Plus less maintenance to worry about.
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