What’s 6th gear for???

Ridgway Jeeper

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1. its a stick shift. you shift into different gears for different situations. accelerating, moving at a steady flat speed, climbing.... etc...
2. Part of the fun of a stick shift, it YOU control how the car revs and accelerates.

I could drive in 4th gear and climb beatifully but rev higher at speed and use for gas. or use 6th on flat terrain and have a smooth lowish rev at speed and have good gas mileage. or use 6th for trying to drive at speed on a climb and watch the car struggle with too high a gear. You control the gearing and can take advantage of the gears that work with the situation.
SAY WHAT?:LOL:
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Down South

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6th in a manual is what I assume what we used to call overdrive. If you are on flat highway and not having to downshift to climb hills, 6th gear should benefit in better fuel mileage, less wear and tear on the engine.
I'd use it cruising on flat roads at higher speeds.
Just MHO.
 

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I've done that using the onboard mileage calculator and found an advantage to 6th... Now I don't trust the onboard calculator to be accurate in an absolute sense, but I expect it to be accurate in a relative sense.

To be clear, final drive ratio in 5th is already taller than 5th in my mustang I had before, so it doesn't really need a double overdrive, but it does help with fuel economy slightly.
That's why I suggested calculating based on actual miles driven and how much gas it takes to fill the tank.

You can't rely on the display on the dash.

I did that experiment. I did better in 5th than in 6th. A lot of people do.

Oh, and try to use the cruise control to manage the exact same speed between runs. That keeps you from inadvertently influencing the results.
 

Zandcwhite

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That's why I suggested calculating based on actual miles driven and how much gas it takes to fill the tank.

You can't rely on the display on the dash.

I did that experiment. I did better in 5th than in 6th. A lot of people do.

Oh, and try to use the cruise control to manage the exact same speed between runs. That keeps you from inadvertently influencing the results.
That experiment would depend entirely on speed driven. A highway loop at 55mph vs a highway loop at 80 mph? One is suited to 5th gear having an advantage, the other 6th gear obviously.
 

PatrickR

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6th in a manual is what I assume what we used to call overdrive. If you are on flat highway and not having to downshift to climb hills, 6th gear should benefit in better fuel mileage, less wear and tear on the engine.
I'd use it cruising on flat roads at higher speeds.
Just MHO.
It's actually a "double overdrive". 5th is already "overdrive", 4th is 1:1. I suspect it was mainly included on account of things like CAFE (paper fuel economy)
 

PatrickR

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That's why I suggested calculating based on actual miles driven and how much gas it takes to fill the tank.

You can't rely on the display on the dash.

I did that experiment. I did better in 5th than in 6th. A lot of people do.

Oh, and try to use the cruise control to manage the exact same speed between runs. That keeps you from inadvertently influencing the results.
Well, I'll have to try that again and see if I get consistent results. Last time was on stock tires.

Like I said earlier, I don't trust the readout as an accurate number, but I would think it can give a relative value (meaning it can tell if you're using more or less gas). I highly doubt it would invert the results.
 

SecondTJ

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If you think 6th gear is useless in a JL, try driving a JK with 3.21 gears.
A 6-speed 3.6 JK w/ crap 3.21 axles (0.797*3.21 = 2.558) is amazingly geared slightly (3%) lower than a 6-speed 3.6 JL w/ 3.45 axles (0.72*3.45= 2.484)
 

omnitonic

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This is why I stepped up to the Rubicon from the start. The 6MT and 3.45 ratio is talked about a lot on the forum, it just isn't a good fit. I see people spending all they saved on the Rubi package on mods it comes with all the time.
Sadly, I didn't discover the forum until I had already bought the Jeep. It is what it is. I didn't know that much about these things going in. I wasn't really expecting the Jeep to become such a central part of my life, for that matter. There were some roads I was too chicken to explore in my truck, but I really had no idea what kind of horizons I was about to open up.

Live and learn.
 

Kreepin1

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Do an experiment. Fill up your Jeep and run a highway loop in 6th gear back to the gas station. Fill up again. Calculate your mileage. Then run the same loop but stay in 5th gear. Fill up again. Calculate your mileage.

I think you'll be surprised at the result.
I too wanted to thank you for the awesome gearing calculator. It's been my go-to tool for pondering tire and gearing changes for many years!

For those that don't know, the JL 6-speed is the Aisin D478 in the drop down list...
 

grimmjeeper

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A 6-speed 3.6 JK w/ crap 3.21 axles (0.797*3.21 = 2.558) is amazingly geared slightly (3%) lower than a 6-speed 3.6 JL w/ 3.45 axles (0.72*3.45= 2.484)
True, but the JK also suffers from a taller 1st gear, 4.46 vs 5.13. The JL with 3.45's has 3.45x5.13 = 17.70 final drive in first. The JK with 3.21s has 3.21x4.46 = 14.32 final dive. And that makes a big difference in daily driving.
 
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SecondTJ

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True, but the JK also suffers from a taller 1st gear, 4.46 vs 5.13. The JL with 3.45's has 3.45x5.13 = 17.70 final drive in first. The JK with 3.21s has 3.21x4.46 = 14.32 final dive. And that makes a big difference in daily driving.
Yes, but the thread is about 6th gear not 1st gear ;)
 

Zandcwhite

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Yes, but the thread is about 6th gear not 1st gear ;)
But 6th gear has nothing to do with driveability. If it's too tall, downshift. I guess you could take off in 4lo to solve the horrible 1st gear problem of the jk's?
 

SecondTJ

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But 6th gear has nothing to do with driveability. If it's too tall, downshift. I guess you could take off in 4lo to solve the horrible 1st gear problem of the jk's?
In terms of driveability, the NSG370 had a much better gear ratio spread than the current AL6.

JK’s problem was the 3.21 axles, not the 4.46 first gear.

Even worse were YJ/TJ with the 3.07 axles and 3.83 first gear
 

Zandcwhite

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In terms of driveability, the NSG370 had a much better gear ratio spread than the current AL6.

JK’s problem was the 3.21 axles, not the 4.46 first gear.

Even worse were YJ/TJ with the 3.07 axles and 3.83 first gear
Agree, to a point. The 5th and 6th gears are far too close and do you really need 2 overdrive gears with a 6 speed manual. The lower 1st gear is still better in my opinion. I guess the 2nd overdrive is why Jeep went with 3.45's though, so it is still a better over all package if you ask me.
 
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