Manual Shift Indicator

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Jan 15, 2020
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SW Louisiana
My DD is a ‘99 4.0 manual TJ. Just curious if any actually shifts according to the indicator on the instrument panel? I find that I can’t even get up to speed with the flow of traffic if I do!
Funny that you ask this. I'm actually currently doing a little experiment to see just how much improvement in fuel mileage I'll see from obeying the shift indicator for a whole tank of gas. Keep in mind, I have 4.11 final drive and 31.5" tires (not too far from stock), and I'm seeing an average of 15 mpg city driving.

So far I've noticed that the indicator tries to keep RPMs as low as 1300 if I'm not trying to accelerate at all. It's moved my shift point about a whole 10 mph lower from how I usually drive. I'm eager (and probably a bit too optimistic 🙂) to see the results next time I fill up and calculate fuel mileage. And I'll be sure to update the thread with my findings.
 

WallyWest

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Nov 6, 2019
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PA
Funny that you ask this. I'm actually currently doing a little experiment to see just how much improvement in fuel mileage I'll see from obeying the shift indicator for a whole tank of gas. Keep in mind, I have 4.11 final drive and 31.5" tires (not too far from stock), and I'm seeing an average of 15 mpg city driving.

So far I've noticed that the indicator tries to keep RPMs as low as 1300 if I'm not trying to accelerate at all. It's moved my shift point about a whole 10 mph lower from how I usually drive. I'm eager (and probably a bit too optimistic 🙂) to see the results next time I fill up and calculate fuel mileage. And I'll be sure to update the thread with my findings.
I would be interested in your results.

I've devoted far too much time over the years looking into this subject. The wide variety of tire sizes and gearing on the Wrangler makes it a very individual thing, but in general shift points are the last thing to worry about. Your overall driving style and the type of driving you do are the primary factors. With most cars your optimum gas mileage is somewhere between 50 - 60mph, in your overdrive gear, and with the torque converter locked up on automatics. Your goal is to get to that point and stay there as much as possible. Any faster, especially with the poor aerodynamics of the Wrangler, and you lose mpg. Any slower, to the point where you downshift or lose the torque converter lock and you lose mpg.

Winding the engine up at low speeds before shifting isn't really a problem, unless you're holding the lower gear after you've stopped accelerating. For constant speed, no acceleration, you should be in the highest gear you possibly can be. But I have experimented with very slow, low rpm accelerating, compared with aggressive acceleration, and have found no real difference in mpg. IF, and that's a big if, you are careful about your target speed. The reason why having a heavy foot on the gas pedal is tied to poor mpg is not really because of the acceleration, it's because most people who do that end up going too fast for traffic/conditions and immediately have to hit the brakes. That's where you kill your mpg, when you hit the brakes. Because all that energy you just spent getting up to speed was totally wasted.
 
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darkmavis

darkmavis

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Nov 3, 2019
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That’s a good idea
I hated that stupid shift light, it tries to get you to shift at rpms that lug the engine. It's there strictly to make the EPA weenies happy. I placed a small piece of black tape over mine to cover it up.
Ha! That’s a great idea! I may have to do that!
 
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darkmavis

darkmavis

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Funny that you ask this. I'm actually currently doing a little experiment to see just how much improvement in fuel mileage I'll see from obeying the shift indicator for a whole tank of gas. Keep in mind, I have 4.11 final drive and 31.5" tires (not too far from stock), and I'm seeing an average of 15 mpg city driving.

So far I've noticed that the indicator tries to keep RPMs as low as 1300 if I'm not trying to accelerate at all. It's moved my shift point about a whole 10 mph lower from how I usually drive. I'm eager (and probably a bit too optimistic 🙂) to see the results next time I fill up and calculate fuel mileage. And I'll be sure to update the thread with my findings.
That’s very cool I’d be interested in the results too! I failed to mention that I’m running 31’s so I’m sure that has something to do with the lugging.
 
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I would be interested in your results.

I've devoted far too much time over the years looking into this subject. The wide variety of tire sizes and gearing on the Wrangler makes it a very individual thing, but in general shift points are the last thing to worry about. Your overall driving style and the type of driving you do are the primary factors. With most cars your optimum gas mileage is somewhere between 50 - 60mph, in your overdrive gear, and with the torque converter locked up on automatics. Your goal is to get to that point and stay there as much as possible. Any faster, especially with the poor aerodynamics of the Wrangler, and you lose mpg. Any slower, to the point where you downshift or lose the torque converter lock and you lose mpg.

Winding the engine up at low speeds before shifting isn't really a problem, unless you're holding the lower gear after you've stopped accelerating. For constant speed, no acceleration, you should be in the highest gear you possibly can be. But I have experimented with very slow, low rpm accelerating, compared with aggressive acceleration, and have found no real difference in mpg. IF, and that's a big if, you are careful about your target speed. The reason why having a heavy foot on the gas pedal is tied to poor mpg is not really because of the acceleration, it's because most people who do that end up going too fast for traffic/conditions and immediately have to hit the brakes. That's where you kill your mpg, when you hit the brakes. Because all that energy you just spent getting up to speed was totally wasted.
I agree. I would reckon that the best mileage is found at the lowest speed of the highest gear.
 
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Jerry Bransford

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I would reckon that the best mileage is found at the lowest speed of the highest gear.
Nope. Lower rpms don't necessarily mean better mpg. For example, my mpg went up nearly 3 mpg after regearing from 4.88 to 5.38 which raised my engine rpms up enough so the engine was running at a more efficient rpm so it wasn't lugging so much.
 
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