This wasn't in the brochure...

[NWJeepr]

"Southern Iowa Hills" = still flat, for those of us who live Rockies and West.

Try downshifting. Stella gave you 6 gears for a reason. If an automatic would grab a lower gear, you should too.

Or you can re-gear your axles and run 2500-3000 rpm in the 70mph range and have a little better crawl ratio off-road.

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[deserteagle56]

Torque is what pulls you down the road. At highway speeds (around 1800 rpm) your 3.6 is putting out around 200 lb-ft of torque. At that same rpm your Cummins is putting out around 600 lb-ft of torque. A world of difference. The torque "curve" of the Cummins is essentially flat - putting out max torque from about 1600 rpm all the way to redline. Your gas engine really is a curve - so if you want that higher torque you'll have to do what others have said - install lower gears to raise your highway rpms and thereby putting you up higher on the torque curve.

Properly engineered turbocharged gas engines can almost imitate a diesel engine by producing a lot of torque down low in the rpm range, and keeping the torque curve flat. Why if you want to tow with a half-ton pickup the F150 with the 3.5 Ecoboost is the recommended engine. 500 lb-ft of torque, an essentially flat torque curve from 1700 rpm on up. And it is why Toyota gave up on the V8 in the Tundra and also went with a twin-turbo V6. Big difference in fuel mileage, though. Start towing heavy with a twin-turbo V6 and your gas mileage will drop to half of what it is when not towing. Towing with the Cummins doesn't make nearly as much difference. My Cummins dually gets 18 mpg empty. Loaded with a 3000+ lb cabover camper and towing my Jeep on a trailer behind it, it still gets 14 mpg. Diesel torque is the difference.

 

[Shibadog]

I had a 4 cyl stick TJ and it took a downshift or two to pull those interstate highway mountains in Iowa. Your JL is a powerhouse in comparison

 

[Murphydog]

FWIW I think gearing is the only choice you have with a manual, unless the cruise control will allow you to down shift.

I have the 8 speed auto, and out west here with high speed limits and big hills it will drop all the way down to 5th to maintain speed.

 

[73TAWM]

Gears may be the answer in your case but my 21 JLU Rubicon with 37s has never had that problem, even in the real mountains. I see other people telling others to re gear when you move up in tire size all the time and in a lot of cases it's very unnecessary.

 

[Ratbert]

392 is your answer...

or cummins swap

I'm not absolutely positive, but I'm thinking @Save The Manuals! prefers driving a manual transmission.

 

[Zandcwhite]

Iowa is not flat. As a native Iowegian who pedaled a bicycle across the state numerous times, I can tell you that for a fact. I drove my new 2024 JLU Sport S MT from Missouri to Iowa last weekend. When I crossed the border and encountered Southern Iowa's hills with the cruise set at 78mph, it quickly fell to 72mph or so before I crested the hill and then it went back up to 78mph. I kinda had to laugh; sure, it's shaped like a brick, what do you expect?? But my 6-speed diesel pickup isn't exactly an aerodynamic fiberglass bullet, and it doesn't do that. However, it has a turbo (Cummins 5.9 liter turbo diesel). Is that the issue here? Is there any way to improve the performance on the interstate?

Iowa isn't flat...The lowest point is within the city of Keokuk, in extreme southeastern Iowa where the Des Moines River enters the Mississippi, at just 480 feet (146 metres) above sea level. The highest spot, Hawkeye Point, is in northwest Iowa at 1,677 feet (511 metres) in elevation. A whopping 1,198' difference between the highest and lowest points. You sound like a girl with an A cup "I'm not flat"... that's a nipple. The .72 overdrive gear won't maintain speed uphill? Shocker. It is a gearing problem, DOWNSHIFT.

 

[Twisted10]

I'm not absolutely positive, but I'm thinking @Save The Manuals! prefers driving a manual transmission.

well lets get a manual in it. anything is possible w enough money and alcohol

 

[autotragic]

I feel like anybody that drives a stick should know you have to downshift for hills. Automatics do it to but people don't pay attention to it as they drive down the road with their lunch in one hand and the phone in the other.

 

[Ratbert]

Iowa isn't flat...The lowest point is within the city of Keokuk, in extreme southeastern Iowa where the Des Moines River enters the Mississippi, at just 480 feet (146 metres) above sea level. The highest spot, Hawkeye Point, is in northwest Iowa at 1,677 feet (511 metres) in elevation. A whopping 1,198' difference between the highest and lowest points. You sound like a girl with an A cup "I'm not flat"... that's a nipple. The .72 overdrive gear won't maintain speed uphill? Shocker. It is a gearing problem, DOWNSHIFT.

Hell, that makes Kansas (679' to 4,039') sound like it's insanely mountainous!

 

[Zandcwhite]

Hell, that makes Kansas (679' to 4,039') sound like it's insanely mountainous!

I'm sure you know people with driveways with more elevation gain than driving from one end of Iowa to the other. I know I do.

 

[Jeep Wick]

Iowa is not flat. As a native Iowegian who pedaled a bicycle across the state numerous times, I can tell you that for a fact. I drove my new 2024 JLU Sport S MT from Missouri to Iowa last weekend. When I crossed the border and encountered Southern Iowa's hills with the cruise set at 78mph, it quickly fell to 72mph or so before I crested the hill and then it went back up to 78mph. I kinda had to laugh; sure, it's shaped like a brick, what do you expect?? But my 6-speed diesel pickup isn't exactly an aerodynamic fiberglass bullet, and it doesn't do that. However, it has a turbo (Cummins 5.9 liter turbo diesel). Is that the issue here? Is there any way to improve the performance on the interstate?

The answer is downshift. 6th is too tall, even on the Rubicon. You should be in 5th on hills, or even 4th with your sport. Even the 8 speed auto will go down a gear or 2. Shift that thing.

 

[Save The Manuals!]

I feel like anybody that drives a stick should know you have to downshift for hills. Automatics do it to but people don't pay attention to it as they drive down the road with their lunch in one hand and the phone in the other.

I have been driving stick shifts for decades.: 1974 VW SuperBeetle, 1974 Jeep CJ5, 1974 Fiat Spider, 1980 Fiat Spider, 1984 Chrysler Laser, 1987 Dodge Daytona, 1992 Mercury Capri, 2006 PT Cruiser, 2003 Ram 2500, 2013 VW Bug TDI, and 2006 Ram 3500. And motorcycles for 16 years (and instructed for 15 years). The only trouble I ever remember having was driving the Capri over the Rockies. I fully understand the concept of matching gears to speed. But this is my first experience with a vehicle needing downshifted on Midwestern hills. Clearly, something is different than what I'm used to, so there is a learning curve required on my part; thus, I am seeking advice of those experienced with JL MTs. I wish to learn what to expect.

 

[Save The Manuals!]

Iowa isn't flat...The lowest point is within the city of Keokuk, in extreme southeastern Iowa where the Des Moines River enters the Mississippi, at just 480 feet (146 metres) above sea level. The highest spot, Hawkeye Point, is in northwest Iowa at 1,677 feet (511 metres) in elevation. A whopping 1,198' difference between the highest and lowest points. You sound like a girl with an A cup "I'm not flat"... that's a nipple. The .72 overdrive gear won't maintain speed uphill? Shocker. It is a gearing problem, DOWNSHIFT.

Shocker that I'm not a mechanic and don't really have a clue what all the gearing numbers being thrown at me really mean. I couldn't begin to tell you what the gearing is on the cars, trucks, and motorcycles I've ridden. I just know that my JL performs differently than anything else I've driven; it FEELS different to me. Sorry I can't put a number--or a cup size--on that.

 

[Save The Manuals!]

Torque is what pulls you down the road. At highway speeds (around 1800 rpm) your 3.6 is putting out around 200 lb-ft of torque. At that same rpm your Cummins is putting out around 600 lb-ft of torque. A world of difference. The torque "curve" of the Cummins is essentially flat - putting out max torque from about 1600 rpm all the way to redline. Your gas engine really is a curve - so if you want that higher torque you'll have to do what others have said - install lower gears to raise your highway rpms and thereby putting you up higher on the torque curve.

Properly engineered turbocharged gas engines can almost imitate a diesel engine by producing a lot of torque down low in the rpm range, and keeping the torque curve flat. Why if you want to tow with a half-ton pickup the F150 with the 3.5 Ecoboost is the recommended engine. 500 lb-ft of torque, an essentially flat torque curve from 1700 rpm on up. And it is why Toyota gave up on the V8 in the Tundra and also went with a twin-turbo V6. Big difference in fuel mileage, though. Start towing heavy with a twin-turbo V6 and your gas mileage will drop to half of what it is when not towing. Towing with the Cummins doesn't make nearly as much difference. My Cummins dually gets 18 mpg empty. Loaded with a 3000+ lb cabover camper and towing my Jeep on a trailer behind it, it still gets 14 mpg. Diesel torque is the difference.

Thanks for the explanation. I hate to think how it's going to perform when I tow my motorcycle behind it...but it'll be WAAAAAAY cooler and more fun!!!!!!

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