2012 Jeep Wrangler JK 3.6 Pentastar V6 - First Drive

    Wrangler Repowered

    John CappaPhotographer, WriterCourtesy of JeepPhotographer

    It was the best worst kept secret. Over a year ago everyone knew the 3.6L Pentastar V-6 would make its way into the ’12 Wrangler. But several questions remained. How much more power would it make than the old (and generally hated) 3.8L minivan V-6 and how would the JK drive on- and off-road with the new engine? We headed up to the mountains of the Lake Tahoe area and on the Rubicon Trail to find out.

    Under the Hood
    In 2011 the Wrangler received a refresh in the form of a new interior. The switch to the Pentastar dual-overhead-cam (DOHC), variable valve timing (VVT) V-6 is really just the second part of that refresh. On paper the new V-6 boasts some impressive numbers. It delivers 285 horsepower for a 40-percent improvement over the old engine. That’s an 83hp increase! Torque is increased to 260 lb-ft for a 10-pecent (23 lb-ft) improvement, and on top of all that, the Wrangler’s fuel efficiency has been increased, too. Some models with the new engine will get up to 21 mpg.

    The Wrangler Pentastar V-6 also has some other pretty cool features. It has an all-aluminum deep-skirt block. Overall it’s more than 90 pounds lighter than the old cast-iron 3.8L it replaces. The exhaust manifolds on the new engine are integrated into the heads. No more cracked or leaky cast-iron manifolds to worry about and no need to upgrade to headers. There is simply a single exhaust flange on each head that is directed right into the equal-length downpipes. In order to make them equal-length the driver side downpipe required a crazy-looking loop-de-loop near the lower control arm mount on the frame. It’s not really in a bad spot but it could be in the way of some aftermarket long-arm suspension lift kits. We wouldn’t recommend removing it because the new engine is said to need it for improved exhaust scavenging, correct backpressure, and increased performance.

    Even the oil filter is an improvement over the old one. The Pentastar V-6 has a no-spill replaceable element similar to what you would find on a heavy-duty diesel engine. No more spills or messy metal canisters to screw with during oil changes. Access to the filter is under a large screw cap on the topside of the engine.

    We also liked the high-mounted and reversed 160-amp alternator. It will most certainly increase the difficulty of changing the serpentine belt, but the up-high location will keep the alternator out of water and mud allowing it live a longer life in applications where the driver likes to go deep-six wheeling.

    A stand-alone transmission cooler was added to keep the auto tranny cool and all Wrangler models will receive a new variable-speed electric fan.

    Backing the new engine is a new automatic transmission. The old anemic-shifting four-speed auto tranny has been replaced with a much more heavy-duty A580 five-speed overdrive automatic. It’s the same tranny that can be found behind the 5.7L V-8 engines and similar to what’s found in the ’11 Grand Cherokee, except it’s not a sealed unit. The Wrangler A580 gets a dipstick but it’s still considered a “fill-for-life” transmission that requires no maintenance. The new auto also comes with Electronic Range Select, a shifter that can be toggled to the right or left to control selection of the desired top gear. The new five-speed auto offers closer ratios as well as a deeper First gear than the older auto. The old auto has a 2.84:1 First, 1.57:1 Second, 1:1 Third, a .69 Fourth, and a 2.21:1 Reverse gear. The new A580 features a much more driver-friendly 3.59:1 First, 2.19:1 Second, 1.41:1 Third, 1:1 Fourth, .83:1 Fifth, and a 3.16:1 Reverse gear. The NSG 370 six-speed manual returns for 2012 and remains mostly unchanged as the standard transmission. The new NSG 370 features a taller .797 Sixth gear Overdrive compared to the .84 Sixth gear of the earlier models.

    Despite the increased power output and improved auto transmission, towing capacity for the two- and four-door models remains unchanged at 2,000 and 3,500 pounds depending on options.

    You’ll immediately notice the increased power of the 3.6L Pentastar V-6 on the street. On a closed course we lined up and raced similarly equipped two-door and four-door ’11 and ’12 Wranglers. We compared the manuals and the automatics several different times in multiple scenarios, including from a dead stop and from rolling starts. No matter how you set it up the ’12 Pentastar-powered Wrangler just kept pulling ahead from the start and continued increasing its lead until we let off the throttle.

    The extra gear in the A580 five-speed automatic transmission allows for tighter gear ratios and crisper shifts. It’s a much sportier-shifting tranny than the four-speed it replaces.

    With the six-speed manual transmission we were able to launch incredibly hard and easily chirp Second gear.

    Jeep claims a 25-percent improvement in 0-60 performance. We crudely timed it ourselves and found that the 3.6L Pentastar-powered ’12 Wrangler supplied a 2.5 second faster 0-60 time than the ’11 3.8L Wrangler.

    Ecstatic that the Pentastar was a significant improvement on-road, we hit the Rubicon Trail to give it a shot off-road. The Pentastar throttle response is more natural than the old 3.8L. It almost feels like it’s cable-operated even though it’s electronically controlled. A topless two-door Rubicon with a manual transmission can easily idle over all but the most difficult obstacles in First gear Low Range, even while manipulating the brake to control speed. The four-door with a manual transmission required slightly more throttle manipulation in the low rpms than the two-door manual due to the extra weight.

    With a 3.59:1 First gear ratio, the A580 auto sports solid crawlability over the old auto’s 2.84:1 First gear. The Pentastar combined with the new five-speed automatic made driving the Wrangler Rubicon off-road effortless; it was so easy in fact that it was downright boring at times. We wanted to get back into the manual transmission Jeep.

    Other Stuff
    Since this is really the second part to the 2011 refresh there aren’t many major changes besides the engine and tranny. However you can now order a Sahara or Rubicon model with a painted top and flares. Previously this was only standard-issue on the Sahara. Although we think it would be cool to get the painted hard top and keep the black plastic flares. You know you will eventually scratch them anyway if you really take it wheeling.

    There are some changes to the axle gearing too. Axle gears include 3.21 (standard), 3.73 (optional, standard on Rubicon with auto tranny), and 4.10 (standard on Rubicon with a manual tranny, optional for Rubicon auto). So 2012 will be the first time the Rubicon will come with 3.73 gears standard in some cases.

    The air conditioning system received an upgrade in the form of a full-face condenser that is 20 percent larger. We noticed that it significantly improved air conditioning performance over the previous generation, especially at slower trail and traffic speeds.

    You’ll also find some new Skittles-like colors available for 2012, such as Dozer Yellow, Flame Red, and Cosmos Blue. Expect to see more bright colors coming in the future.

    Base model Wranglers won’t see a price increase for 2012, but the Wrangler Sahara and Rubicon will see up to a couple hundred dollars tacked on to the 2011 cost.

    Bottom Line
    Look, it’s not the V-8 that we all wish it was, but we think the 3.6L Pentastar V-6 will be enough to chew into the Hemi V-8 swap market. And it will surely decrease the used-car value of the ’07-’11 3.8L V-6 powered Wranglers, at least for the enthusiast market. When comparing the dyno charts you’ll see that the new 3.6L engine makes slightly less torque under 1,400 rpm, but in the real world behind the wheel you don’t notice it because of the improved throttle response on the manual tranny version and both the improved throttle response and the deeper gearing on the automatic tranny version. And from 2,000 rpm on up the 3.6L puts the old motor to shame thanks in part to the extremely flat torque curve.

    The Pentastar is a pretty advanced motor and will probably stick around for a while. It has lots of potential, not just because it will eventually be the only V-6 in the Chrysler lineup, but because off into the future it can very easily be set up for direct injection, a turbo, or even twin turbos. Hmm, hey Jeep executives, how about a factory ORT (Off-Road Technology) Wrangler with a turbo?