Help with JK Rubicon models (from a Land Cruiser guy)

Comanche Scott

Expedition Leader
$40K goes a long way to freshening up your FJ40. You are right, they are amazing vehicles.
Not going to depreciate either, so as long as the mods are well engineered and carried out, you'll be money ahead.
 
landcruiser vs jeep

I owned a 99 fj 100 last year I could find with center lock and rear lock It was great loved it until the computer went out and was told $$$$ to fix it. I have also owned many toy from the first 4x4 in 82 3 of those and 2 forerunners number of american 4x4s and my first 4x4 was a 77 cj-7 golden eagle package with a 304 v8 and auto. I have not owned an fj 40. Always wanted one. but everyone I ever talked to said the motor was grossly underpowered and many of those guys swapped in chevy v-8s. I have heard that the axles birfield joints ( not sure exactly if this is true )have problems. That beingsaid I now drive a jeep wrangle rubicon it is an 08, It has the lifetime drivetrain warranty I have only had on major problem with it and that is a blown transmission which chrysler paid for at about 106,000. I have 130,000 now and it runs just fine It is built pretty heavy winch warn bumper rock sliders and back bumper It is lifted with an ome 4 inch lift ( dueot he unbelievably heavy warn bumper 155 lbs with out the winch .

Agues my point is that all vehicles have issues. I don't thing the fj 40 is near as comfortable as my wrangler. it may have a stouter frame . I am running 315s 34.5 dia on the stock axles and with out re gearing and haven't had any issues but if i do its covered limited life time warranty = 99 years. no baloney,

I almost bought a 2015 4 door rubi with the hard rock package but Get this >>>> My service rep says why? the new jeep is better sure but not that much better..

all in all if I din't have the limited life time power warranty I would probably by that rubi with the hard rock package and an auto
 

Dan Grec

Expedition Leader
The 3.6 had some head problems (bad machining) in early build 2012's and water pumps that squeeled through early 13 models. My JKUR had the sqeeky water pump, which was warrantied. They seem to have worked those problems out as well as an automatic shifting problem with Rubicon's in 4 low.
Does anyone know if the bad heads in the early 2012s are an immediate replace under warranty, or will they only replace it if it shows symptoms?


Thanks,
-Dan
 

MTSN

Explorer
I owned a 99 fj 100 last year I could find with center lock and rear lock It was great loved it until the computer went out and was told $$$$ to fix it.
What "computer" are you speaking of? I've never heard of any UZJ100 computer failures.
 
Does anyone know if the bad heads in the early 2012s are an immediate replace under warranty, or will they only replace it if it shows symptoms?


Thanks,
-Dan
Only if it shows a symptom. This usually is a check engine light for P0300, P0302, P0304, and/or P0306 fault codes (misfires on the even cylinders). Many reported ticking noises from the valvetrain. Mine never made any noise, just an intermittent, progressively more perstistent P0300 code at around 30K miles, and the dealer then swapped the cylinder head under warranty. There is a warranty extension on 2012's for this specific issue. I also had a squeaky water pump replaced at the same time.
 

Dan Grec

Expedition Leader
Only if it shows a symptom. This usually is a check engine light for P0300, P0302, P0304, and/or P0306 fault codes (misfires on the even cylinders). Many reported ticking noises from the valvetrain. Mine never made any noise, just an intermittent, progressively more perstistent P0300 code at around 30K miles, and the dealer then swapped the cylinder head under warranty. There is a warranty extension on 2012's for this specific issue. I also had a squeaky water pump replaced at the same time.
Thanks.

Is there an accepted number of miles whereby if it hasn't shown symptoms then it likely won't?

Thanks,
-Dan
 

greg.potter

Adventurer
Does anyone know if the bad heads in the early 2012s are an immediate replace under warranty, or will they only replace it if it shows symptoms?


Thanks,
-Dan
They will only replace the driver's side cylinder head if it shows very specific symptoms. There is another less publicized issue with premature valve train wear on the early 3.6L Pentastars. According to the dealers Jeep service specialist the heads have gone through 3 major revisions and the rocker arm assemblies have gone through 4 revisions since the initial release. At about 120K kilometers my 2012 starting making a lot of valve train noise. Just shy of 150K kilometers it got quite bad and I took it into the dealer. The dealer advised that they had seen the problem with premature valve train wear a fair bit on the early Pentastar's but Chrysler was not offering any warranty on the issue. My initial contact with Chrysler on the issue was less than satisfying. Which reminds me - I need to follow up with them on the issue again.
 

mikejr

New member
I've had two JKs, and been a member of the local Jeep club for 10+ years. I would look for a 2012 or newer, when you buy check the lockers and disco.
 

RubiconGeoff

Adventurer
The 3.8 with the automatic transmission sucks, even with 4.10 gears and stock size tires. Upsize the tires and you're in even worse shape. A friend has a 2008 Rubicon that I've driven both stock and with 35's, and I'm not a fan. The transmission's ratios are horribly mismatched to the engine's output, and really give the 3.8 a bad reputation for being terribly underpowered.

The 3.8 with the manual transmission is absolutely fine. I found my Rubicon to be geared pretty low with 4.10 gears and stock tires (I usually started off in 2nd gear on the street) but upgrading to 33-35" tires puts the gearing spot-on. With 35's I pull most regular grades in 6th gear even towing my lightweight camp trailer. When I'm traveling in a group of mixed vehicles through the mountains, I'm not the slow one even when pulling my trailer on steep grades. To the contrary, my Jeep is one of the faster vehicles in the group, and with 6 gears to work with, I always have the right ratio available. I've never found myself needing any more power than the 3.8 provides.

Another friend of mine has a 2012 Rubicon, and other than its automatic transmission it's built nearly identical to mine. On steep mountain grades where I just hold the throttle to the floor in 4th gear, his transmission hunts constantly, with a big jump between bogging in 4th and then zinging in 3rd. Back and forth, back and forth between the gears, which he finds quite annoying. We have one long high-altitude grade that we frequently drive together; with both of our transmissions in 3rd gear, he can't meaningfully pull away from me. His 3.6 has slightly more power, but with the different gear ratios between our two Jeeps, in the real world that 3.6's 83 additional horsepower doesn't manifest in a substantial difference.

The 3.8 has more off-idle torque than the 3.6. The newer motor catches up by medium RPMs, but then walks away from the old motor in the high RPMs. The 3.8 feels like more of a "truck" engine, while the 3.6 is more of a "car" engine in how their horsepower and torque curves behave.

The 3.8 is an older, low-tech engine design. It's much simpler to work on than the 3.6, and Chrysler produced hundreds of thousands of these engines and worked out most of the "bugs" before introducing it to the Wrangler. Most of the "problems" with this engine seem to stem from Chrysler specifying an overly thin oil viscosity (5W-20) in the final years of this engine's production in an attempt to eke out a little bit better fuel economy. I run 10W30 and have had none of the oil consumption people have complained about, nor any other problems with my 3.8.

The 3.6 is a much more modern engine design, and as with most brand-new engines it had some "teething" problems in its first couple years which seem to be fixed now. The 3.6 is a great engine, but I wouldn't necessarily say it's a must-have. If you find an earlier Wrangler at a good price, don't be scared of the 3.8 (unless it has that awful 4-speed auto behind it). If you want a Jeep with an automatic, don't even consider a 2007-2011 model.
 

jackflash

Observer
I have seen a number of posts here about how bad the 2011 JK is or how it is the "worst of both worlds". Just wondering why this is?
 

mikejr

New member
All of the JKs are fine, some are just more desirable than others.

2007-2011 3.8 Motor:
+ Reliable
- Consumes oil in many cases (always check!)
- Low power
- Auto transmission underperforms

2012+ 3.6 Motor
+ Excellent power
+ Better fuel economy
+ Auto transmission performs
- Some early units had head issues

2007-2010 Interior
+ Easy to clean
+ Feel's very Jeep'ish
- No Armrests on door
- Headrests (these things should be banned via Geneva convention)
- Seat cloth - mesh is impossible to clean easily

2011+ Interior
+ Armrests on doors
+ Center console is a little bigger, better armrest
- Chrome and silver...
- Looks terrible dirty, harder to keep clean
- Feels very Fiat'ish

Basically the newer you buy, the better off you will be. 2013 and up even have trimmed pinch seams - several small QoL changes occur over the years.
 

JIMBO

Expedition Leader
:sombrero: The 3.8l v6 is the last of the IRON BLOCK, V6 engines that Chrysler produces and has over 24 years service/history--

The 3.8 with the automatic transmission sucks, even with 4.10 gears and stock size tires. Upsize the tires and you're in even worse shape. A friend has a 2008 Rubicon that I've driven both stock and with 35's, and I'm not a fan. The transmission's ratios are horribly mismatched to the engine's output, and really give the 3.8 a bad reputation for being terribly underpowered.

The 3.8 with the manual transmission is absolutely fine. I found my Rubicon to be geared pretty low with 4.10 gears and stock tires (I usually started off in 2nd gear on the street) but upgrading to 33-35" tires puts the gearing spot-on. With 35's I pull most regular grades in 6th gear even towing my lightweight camp trailer. When I'm traveling in a group of mixed vehicles through the mountains, I'm not the slow one even when pulling my trailer on steep grades. To the contrary, my Jeep is one of the faster vehicles in the group, and with 6 gears to work with, I always have the right ratio available. I've never found myself needing any more power than the 3.8 provides.

Another friend of mine has a 2012 Rubicon, and other than its automatic transmission it's built nearly identical to mine. On steep mountain grades where I just hold the throttle to the floor in 4th gear, his transmission hunts constantly, with a big jump between bogging in 4th and then zinging in 3rd. Back and forth, back and forth between the gears, which he finds quite annoying. We have one long high-altitude grade that we frequently drive together; with both of our transmissions in 3rd gear, he can't meaningfully pull away from me. His 3.6 has slightly more power, but with the different gear ratios between our two Jeeps, in the real world that 3.6's 83 additional horsepower doesn't manifest in a substantial difference.

The 3.8 has more off-idle torque than the 3.6. The newer motor catches up by medium RPMs, but then walks away from the old motor in the high RPMs. The 3.8 feels like more of a "truck" engine, while the 3.6 is more of a "car" engine in how their horsepower and torque curves behave.

The 3.8 is an older, low-tech engine design. It's much simpler to work on than the 3.6, and Chrysler produced hundreds of thousands of these engines and worked out most of the "bugs" before introducing it to the Wrangler. Most of the "problems" with this engine seem to stem from Chrysler specifying an overly thin oil viscosity (5W-20) in the final years of this engine's production in an attempt to eke out a little bit better fuel economy. I run 10W30 and have had none of the oil consumption people have complained about, nor any other problems with my 3.8.

The 3.6 is a much more modern engine design, and as with most brand-new engines it had some "teething" problems in its first couple years which seem to be fixed now. The 3.6 is a great engine, but I wouldn't necessarily say it's a must-have. If you find an earlier Wrangler at a good price, don't be scared of the 3.8 (unless it has that awful 4-speed auto behind it). If you want a Jeep with an automatic, don't even consider a 2007-2011 model.
Agree, especially on the 3.8l and the auto is comfy/w gears !

It has never been an underpowered v6--the reason for that feel is the lousy gearing and combo/w the 42RLE 4spd auto-

Mine is flawless and by re-gearing the diff's, you have a very economical/peppy/dependable jeep-

It'll depend on your finding a deal that you want-

Good luck

:costumed-smiley-007:wings: JIMBO
 

nwoods

Expedition Leader
minor edits in bold below. Also, what year was it they moved the subwoofer? That's a good improvement.
All of the JKs are fine, some are just more desirable than others.

2007-2011 3.8 Motor:
+ Reliable
- Consumes oil in many cases (always check!)
- Low power
- Auto transmission underperforms

2012+ 3.6 Motor
+ Excellent power
+ Better fuel economy
+ Auto transmission performs
- Some early units had head issues

2007-2010 Interior
+ Easy to clean
+ Feel's very Jeep'ish
- No Armrests on door
- Headrests (these things should be banned via Geneva convention)
- Seat cloth - mesh is impossible to clean easily
- Kills the knees of anyone over 6'-4" (those vertical blades on each side of the center stack. Ouch!)

2011+ Interior
+ Armrests on doors
+ Center console is a little bigger, better armrest
+ Accommodates tall drivers fairly well
- Chrome and silver...
- Looks terrible dirty, harder to keep clean
- Feels very Fiat's
+/- Wife will like it better

Basically the newer you buy, the better off you will be. 2013 and up even have trimmed pinch seams - several small QoL changes occur over the years.
 
2012 JKU sport with the 3.6 and a manual transmission
ARB's f/r with 4.56 gears and 35" tires

only thing done mechanically with mine outside of normal fluid changes were the gears/lockers and got the clutch replaced at 110k miles never had an issue with the heads and it has 117k right now
 

Mass_Mopar

Keep it simple stupid
minor edits in bold below. Also, what year was it they moved the subwoofer? That's a good improvement.


The subwoofer moved in '15. My 14 has the "old" style that sticks out from the hinge side of the door. My '15 has it built into the cubby under the floor.
 
Top