best mod for my jk
- Thread starter sgt rock
- Start date
I (almost) feel bad that my Hemi swap worked out so well and yours didn't.
If you haven't gotten a lift yet, I'd really highly recomend the AEV lifts. They offer a 4.5" lift, a 3.5" lift and either have just come out with or are about to come out with a 2"-2.5" lift. Their premium lifts address oem steering and handling issues that no one else addresses as well and their lifts are designed from the start to handle the increased weight an expedition truck will carry, or even a rock crawler will carry.
JPK
It was my interstate driving that was the deciding factor on my Hemi swap. My hunting clubs are a couple hours away via intersate and so are the mountains. I got tired of the highway performance and ride of my LJ and started borrowing my wife's JKU Rubicon. That was a huge improvement, but I got tired of the Jeep not being able to maintain speed on the interstate and the auto trans always making that dramatic shift down out of O/D.
After looking for alternatives I gave AEV a call and told them that what I was looking for was a Jeep that was the comfortable and brainless highway cruiser that my Suburban is but that was as capable off road as my LJ when I got where I was heading.
Jeff Clark of AEV's answer was, "Well, that's what we do..." They delivered!
My wife's JKU Rubicon has a 2.5" Teraflex BB, spidertrax spacers and is otherwise stock. All in average is 17-18mpg with variable light to medium loads.
M JKU averages 12-13mpg with generally heavier loads. My LJ, with the 4.0, averages about the same, or maybe worse.
More than half of your JKU problem is with the auto trans, imo. Its a three speed auto with third at 1:1 and then a too damn big leap to O/D fourth at ~.69:1. The Hemi trans is a five speed with a gear between the JKU's third and fourth. So the top gear in the five speed is close to the top gear in the JKU four speed, actually slightly taller at ~.67:1, but the huge gap between the four speed's top two gears is gone. The difference is very significant.
Before committing to a Hemi swap, you may want to look into the coming '12's which will have the Pentastar, which will offer ~30% more HP and torque than the 3.8l but most impotantly will also offer a five or six speed auto trans.
I believe that the five or six speed trans will eliminate almost all of the issues that auto JKU's face now and most of the griping about performance. The Pentastar will be a nice bump up, but the trans will be the real leap forward.
I think the cost of trading out of your 2007 and into a 2012 would be less than the cost of going Hemi.
If Jeep would offer the JKU with a V8 engine that put out ~300 HP and lbs/ft of torque it would be perfect. At 375 hp and ft/lbs the Hemi is more than enough. Unfortunately, the Pentastar isn't going to be the perfect Jeep engine because it will still be a bit light on power, but mostly because its HP and torque are produced futher up the rpm band.
If you do decide to go Hemi, than I have to recomend AEV for the swap, or their premium swap kit. One thing to ponder: The Hemi puts out more torque at 1200rpm than the 3.8l puts out max.
JPK
dsy
Adventurer
Another extremely happy Hemi JKU owner here. Over 30,000 trouble free miles since I did my own swap and I still get a big grin on my face when ever I drive it. Around town driving I avg 12.5 but cross country pulling my trailer I avg a little over 15mpg. Last time I had it out in AZ it got up to 115 deg every day we were there but the temp gauge never crossed the 1/2 way point.
Is there a story as to why Burnsville did not make it right? If I would have spent upwards of 20 grand and not gotten what I thought I was paying for I would have been making a whole lot of noise. I dont think I could have given up and gone back to the anemic 3.8 :Wow1:
Doug
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BTW, as an aside to this for all JK owners. I have the aero force scan gauge and the stock dash gauge gets to the middle at 180degrees, and doesn't move upward till it gets past 230degrees. I found this out as I towed my little trailer up the passes in CO on I70 last summer.
mikE(closer to being on topic)
alosix
Expedition Leader
DUDE!!! awesome.. I've been dying to know the range of that gauge on a JK.
For now (until I get my canbus gauge driver coded/built).. I've been using a dashhawk to keep an eye on my M725's Hemi.
The engine does seem to want to run a little higher than I thought it would on the dashawk. I think I'd almost rather have the vague gauge as seeing the temp move around as much as it does (I've had the back of this 6,000lb truck filled to the top with Rubicon Express lift kits at one point) under load.
RubiconGeoff
Adventurer
This is the norm with modern vehicles. Dealers & manufacturers got tired of numbnuts bringing their vehicles in to be "fixed" when their gauges move around during normal operation. They "dampen" the gauges' indication so that the needle sits rock-steady in the middle during the full range of "normal" operation. That's why a good ScanGauge or UltraGauge is a great addition to any enthusiast's OBDII vehicle.
Since this seems like wanted info. The scan gauge says that the thermostat is 190. Runs there most of the time. Climbs to 200-205 on long uphills, but drops right back on the downhill.
Other info is the scan gauge thinks the trans(auto) runs at about 130 humming down the interstate with my 5" x7" aux cooler in front of the radiator.
Engine makes about 85hp at 2800rpm here at 700' elevation. Looses about 5hp/1000' of elevation gain. Makes 100% engine power at about 35% throttle at the 2800-3300rpm range.
All that info is from the scan gauge, so take it as you will.
mikE(it's good entertainment while driving)
sgt rock
Adventurer
I'll be at Easter Jeep Safari in Moab this spring. I'm planning to arrive Sunday the 18th. LONG 2100 mile drive for me and a friend. See you there?
JPK
http://www.aeroforcetech.com/products_interceptor.html
You can kinda see it in this pic on the left of the dash.
mikE(just mounted in a cup on top of the dash)