We Test The New Pentastar Powered Wrangler On The Rubicon Trail
The current version of the Wrangler, known internally as the JK, was a pretty big deal when it debuted in 2006 as an ’07 model. Not only did it offer a complete rethink of the venerable TJ, but it also brought the Wrangler in to the mainstream with its four-door Unlimited model. At the time of the JK introduction we were happy to see a manual transmission, more refinement, and a spacious interior. No longer did you have to choose between your camping gear and your loved ones, and solid axles and a fold down windshield ensured the Wrangler’s capability and heritage remained intact.
The Wrangler JK was an instant success as new customers and the aftermarket embraced it, carrying many of the companies who produced aftermarket parts for it during the economic downturn. It has even been said that the Wrangler JK is the product that saved Jeep, which is the brand that saved Chrysler. If not for the JK, the off-pavement enthusiast landscape could look completely different now.
Since its launch, the JK has gone on to dominate every test we have thrown at it, beat sales expectations on a regular basis and lead the renaissance of the Jeep brand. It is a product that carries a lot of weight and responsibility within the walls of the Jeep brand. So how do you make it better without messing up the formula?
At the time of its introduction, we leveled two distinct complaints about the Wrangler, the interior materials were cheap and the engine was underpowered, especially with the antiquated four-speed automatic. For 2011, Jeep answered our interior criticism with a stunning new dash, as well as some NVH improvements. For 2012, the last piece of the puzzle comes in to place as Chrysler’s newest corporate engine, the 3.6L Pentastar V-6, finds a home under the JK’s hood. This is a thoroughly modern mill that is teamed up with a new-to-Wrangler five-speed automatic or the existing six-speed manual transmissions.
Jeep invited us to the California-Nevada border to test Jeep’s latest Wrangler on the storied Rubicon Trail and in and around scenic Lake Tahoe. After a few days in the driver’s seat, here is what we found.
The all-aluminum Pentastar V-6 produces 285hp and 260 lb-ft of torque in JK trim, which is an increase of 83 horsepower and 23 lb-ft of torque, or 30 percent for horsepower and nine percent for torque over the outgoing 90-pound-heavier 3.8L V-6. While nine percent may not sound like much, the 3.6L has an impossibly flat curve, which translates into more power over a greater rpm range.
To get an idea of just how much more power the 3.6L makes over the 3.8L, one just needs to take a look at the dyno overlay. The 3.8L hits 200 lb-ft at around 1,900 rpm and carries it to about 5,300 rpm, near its 5,600 rpm redline. With the 3.6L, 200 lb-ft of torque comes in around 1,500 rpm and it never drops below 200 all the way to its 6,500 rpm redline. In fact, the 3.6L hits 250 lb-ft (13 lb-ft more than the 3.8L max) at 2,100 rpm and doesn’t drop below 250 lb-ft until 5,300 rpm. It is real-world power that you can feel and finally the JK feels competent while passing on two-lane roads.
Backing the Pentastar is the same Getrag NSG 370 six-speed manual found behind the 3.8L, marking the Wrangler as Chrysler’s very first use of the Pentastar/manual in a longitudinal arrangement. The six-speed has been updated with a new clutch housing, flywheel, and long travel damper clutch. It still has a 4.46:1 First gear, making the max crawl ratio available from the factory (4.10:1 axle, 4.0:1 transfer case) 73:1, the same as the 2011 manual-equipped Wrangler.
While we are excited that you can still get a manual with the JK, the bigger news is in the optional W5A580 five-speed automatic that is shared with the Grand Cherokee. In addition to an extra cog over the retired 42RLE, the W5A580 has a lower First gear than the 42RLE (3.59:1 vs. 2.84:1), improving the crawl ratio on automatic-equipped Wranglers to an impressive 58.9:1 from 46.6:1. It also now has Electronic Range Select (ERS), allowing the driver to select the appropriate gear for better control over the drivetrain, and the extra gear helps to lower interior noise levels on the highway. While the transmission is designed to be “filled for life” and doesn’t require maintenance in normal operation, the Jeep engineers added a dipstick, knowing that Wrangler owners are more likely to drive in extreme environments and want to know the condition of their transmission fluid.
Together, the new engine and transmissions improve fuel economy across the board by as much as 2 mpg, and for the first time the Wrangler is capable of 20 mpg on the highway. The lowest rated Wrangler is the Unlimited automatic with an EPA rating of 16 city/20 highway, while the two-door, manual or automatic, is rated at 17 city/21 highway, giving an impressive highway range of over 400 miles on Unlimited models.
Jeep didn’t stop at the driveline to bump up refinement. Optional are automatic climate control, heated seats, and power mirrors (new for 2011), and they improved NVH and interior comfort through improvements in powertrain mounting, noise damping, and a new acoustic engine cover. Other notable highlights are the availability of a body-colored top and flares on Rubicon models and a wider selection of gear ratios, including taller gears for those who don’t plan to wheel or modify their JK. What this means for those of us planning on bigger tires is that if you are presently running 37s and 5.13:1s with your current 3.8L-powered JK, you can probably have the exact same package, but run 4.88:1s in a 2012, which should help fuel economy and pinion strength.
As for the rest of the JK, the chassis is the same fully boxed, high-strength steel frame with seven crossmembers and 10 body mounts on two-doors and eight crossmembers and 12 body mounts on Unlimiteds. Axles are also identical, which means the aftermarket should have no problems adapting current JK upgrades, such as suspension kits, skidplates, gussets, and gears to the ’12 models.
Three new colors join the pallet for 2012: Dozer Yellow (think bulldozer), Deep Molten Red, and Crush Orange in addition to eight other familiar hues.