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Old 06-27-2013, 09:41 AM   #31
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on a test drive, i drove a 2001 4.0L 5-speed then 10 minutes later jumped into a 2006 4.0L 6-speed. The 6-speed felt better. But not by much.

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Old 06-27-2013, 10:37 AM   #32
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You will get your powerband back as well as 6th gear for hills and you will enjoy it when off-roading. Some will tell you not to regear, but it will be better for trails and highway driving. Yes you will have higher rpm's with 4.88's or 4.56's but that doesn't mean less mpg. Depending on what size tire you are going to will also determine which gear to choose. Most of the charts don't represent the 6 speed ratios, so it takes a bit of research to get the ideal gear set up.
There is a huge debate to regear or not to regear and it comes down to money, what type of wheeling, other upgrades you have and tire size.
I run 33's and 3.73's, but I have 4.88 gears and 35's to install which will be ideal for all of my concerns. I also have adjustable control arms, 3" springs, currie steering, (black magic brakes are coming) plus a ton of other upgrades.

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Old 06-27-2013, 12:44 PM   #33
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Quote:
Originally Posted by Verf View Post

Since I'm the OP, gonna kinda hijack my thread a bit. Briefly explain the gearing. My (lack of) understanding is the lower the number, the better on gas i.e. 3.73's will get better mileage vs 4.10

However, I read a lot on here where 4.56 or 4.88 gears are great on our Jeeps. My guess is my thinking is way off and I've been thinking wrong for years. I'm a motor guy and really don't know squat about driveline stuff.

Thanks,

Butch
I'm running 33s on the stock 4:11s. I used to have a very bad habit of not downshifting, for grades or headwinds, thinking I was still in the diesel powered 18 wheeler... As a result my mpg suffered, and when i finally did downshift, it was too late. I,ve since learned to " stay on top of it".....With shorter gears i could stay in the " big hole" and not have to downshift nearly as much, and the Mpgs would not suffer .
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Old 06-27-2013, 08:36 PM   #34
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Quote:
Originally Posted by Verf View Post
Briefly explain the gearing.

Very briefly ...

when you increase tire diameter you should go to a numerically higher rear end gear to keep the engine in the proper rpm range while driving.


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My (lack of) understanding is the lower the number, the better on gas i.e. 3.73's will get better mileage vs 4.10

With a significantly larger diameter tire the numerically lower rear end gear can actually be worse for mileage as the engine will be "lugging" (not operating in the proper rpm range) when compared to driving in same transmission gear with a numerically higher rear end gear.
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Old 06-28-2013, 04:11 PM   #35
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Quote:
Originally Posted by Verf View Post

Since I'm the OP, gonna kinda hijack my thread a bit. Briefly explain the gearing. My (lack of) understanding is the lower the number, the better on gas i.e. 3.73's will get better mileage vs 4.10

However, I read a lot on here where 4.56 or 4.88 gears are great on our Jeeps. My guess is my thinking is way off and I've been thinking wrong for years. I'm a motor guy and really don't know squat about driveline stuff.

Thanks,

Butch
I actually get slightly better gas miliage with 33's and 4.88's than i did with 3.73's and 30's.....its due to the shift points being better centered with the engine's optimal cylinder fill which resides between 2400-3200 rpm's.
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Old 06-29-2013, 09:07 AM   #36
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.its due to the shift points being better centered with the engine's optimal cylinder fill which resides between 2400-3200 rpm's.
How do you know that that rpm range has "optimal cylinder filling"? My experience is that peak torque is roughly 3000-4000 rpms, but it's pretty much within 15ftlbs from 1500-4000 rpms.
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Old 06-29-2013, 09:31 AM   #37
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How do you know that that rpm range has "optimal cylinder filling"? My experience is that peak torque is roughly 3000-4000 rpms, but it's pretty much within 15ftlbs from 1500-4000 rpms.
And within 2400-3200 rpm tq(cylinder fill is the highest/most efficient)is within 5 foot pounds and is basically the peak of the tq. curve. Past 3200 the tq slowly tapers off.
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Old 06-29-2013, 10:45 AM   #38
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Past 3200 the tq slowly tapers off.
Not in my experience. Its more like 4500.
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Old 06-29-2013, 11:09 AM   #39
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Not exactly the best "google" dynochart to use for a 4.0L. The 4.0L powerband is wide, but its optimal range peaks at 3200rpm. The resolution and multipass overlays on that dyno plot won't really show that.
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Old 06-29-2013, 11:19 AM   #40
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That is my jeep on my dyno. It's hard to argue with real data.
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Old 06-29-2013, 07:46 PM   #41
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Wait a minute, you guys are quibbling over torque and HP specs? The bottom line, regardless of where the peak HP and torque are, (3200-4000 rpms,) No one in his right mind operates their vehicle at the peak of the power band. That's just blowing fuel out the pipe.. Efficiency is what the OP, and many others are concerned with... These 4.0s are arguably the most efficient at right around 2100 to 2300 RPMs.. Granted, 2100 is at the very beginning of the output band, but that is where efficiency comes into play... Ie the most torque and HP for the dollar, and for healthy running of the engine... If I were shopping for a used 4.0 and the OO told me he habitually wrapped it up above 3,000 rpms I'd run away,, run away!! Pulling a load, up hill, or some 20 mph headwinds, then by all means crank that baby up, but not for normal operation... Just my 2 cents
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Old 06-29-2013, 08:22 PM   #42
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Originally Posted by UnlimitedRubicon View Post
I use first gear because I drive a Wrangler not a sports car.
So if you're driving a sports car you don't use first gear?

Damn.... and all these years I've been using first gear whether I was driving a Wrangler OR a sports car..... What a waste!!!!


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Old 06-29-2013, 08:38 PM   #43
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Quote:
Originally Posted by Rubicondon53 View Post
These 4.0s are arguably the most efficient at right around 2100 to 2300 RPMs.

In a theoretical, static situation, yes. In the real world, no.


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If I were shopping for a used 4.0 and the OO told me he habitually wrapped it up above 3,000 rpms I'd run away,, run away!!

Have you looked at your tachometer lately? Where is the redline?



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So if you're driving a sports car you don't use first gear?

Damn.... and all these years I've been using first gear whether I was driving a Wrangler OR a sports car..... What a waste!!!!



smart remark - FAIL

The low first gear in the NSG370 usually necessitates a short (duration of time) shift to second which is not conducive to driving the Wrangler like a sports car.
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Old 06-29-2013, 09:05 PM   #44
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I've always disliked 6 speeds - in whatever application. It's just gear clutter - too many gears, too much shifting.

There's a lot myths about fuel economy and number of gears. Most people think 6th gear of a six speed is necessarily taller than 5th gear of a five speed, which is obviously bunk. It depends on what gears they put in the transmission.

More gears is usually more efficient for an automatic but not for a stick, because shifts are inefficient and the more of them you have the less efficient you will be. This is why cars like Corvette are programmed to skip gears in order to avoid gas guzzler tax. Saab once did an extensive study and report and came to the same conclusion - for better fuel economy on a stick - skip gears.

The EPA tests have confirmed this repeatedly over the last several decades - both in the transition from 4 speeds to 5 speeds and the transition from 5 speeds to 6 speeds. All else equal fewer gears on a manual transmission gets better mileage. The Wrangler transition to 6 speed is an example - the 2004 five speed gets better mileage than the 2005 six speed - same 4.0L engine, same 3.07 rear axle ratio, just more shifting on the six speed. (The EPA test requires shifting through all available gears on a manual.)

This idea that more gears brings fuel economy is a powerful myth and manufacturers are now pretty much stuck with it.
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Old 06-29-2013, 09:10 PM   #45
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Originally Posted by UnlimitedRubicon View Post

In a theoretical, static situation, yes. In the real world, no.

Have you looked at your tachometer lately? Where is the redline?

smart remark - FAIL

The low first gear in the NSG370 usually necessitates a short (duration of time) shift to second which is not conducive to driving the Wrangler like a sports car.
What does the redline have to do with efficiency? Of course, my jeep runs like a well oiled top at 3200 rpms, but if it pulls efficiently at 22 to 26, why would anyone want to blow fuel out the stack for something not needed? My point is efficiency, which =s,, the most amount of torque and HP per energy used... It's a bargain we all make with our energy consumption every day.. You cannot tell me that you prefer to run your jeep at 70 mph in 4th gear at 2800 rpms, when operating in 5th at 2400 at 70 gets the same result with less energy expended.. Yes my friend, that's the real world, not a static environment.. I haven't even gotten into the wear and tear on the engine... These motors are good for a quarter million miles, given they are normally operated at the bottom end of the torque band, 2100-2700 rpms... Run them constantly at 3000 rpms and up? Just take 75 to 100 thousand miles off of that quarter million... Do I know where the redline is? I have no words...
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Old 06-30-2013, 08:25 AM   #46
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What does the redline have to do with efficiency? Of course, my jeep runs like a well oiled top at 3200 rpms, but if it pulls efficiently at 22 to 26, why would anyone want to blow fuel out the stack for something not needed? My point is efficiency, which =s,, the most amount of torque and HP per energy used... It's a bargain we all make with our energy consumption every day.. You cannot tell me that you prefer to run your jeep at 70 mph in 4th gear at 2800 rpms, when operating in 5th at 2400 at 70 gets the same result with less energy expended.. Yes my friend, that's the real world, not a static environment.. I haven't even gotten into the wear and tear on the engine... These motors are good for a quarter million miles, given they are normally operated at the bottom end of the torque band, 2100-2700 rpms... Run them constantly at 3000 rpms and up? Just take 75 to 100 thousand miles off of that quarter million... Do I know where the redline is? I have no words...
Less shifts to get to a specific speed point may very well be more economical in terms of fuel but can be less efficient in terms of keeping the powerband in the optimal range. The Jeep 4.0L isnt exactly a powerhouse. My older TJ with the 5 speed always felt like it was lacking in the gearing dept. 1st and especially the steep 5th OD never felt right in em.....always felt like power was lacking. The 6 speed is definetly a much better match IMO, especially the OD 6th gear.
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Old 06-30-2013, 09:12 AM   #47
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My .02, Off topic. This Cruise RPM thing all comes down to what makes you get down the road at the lowest RPM while maintaing the most economical engine vacuum. Simple terms, it's how far you are having to push down on the throttle pedal and maintain vehicle speed. So with that in mind your load going down hill can dictate no throttle at all. That is really the best fuel economy and idle RPM if possible lol to be at for a given set up. Going up hill is the same situation except you are using the throttle to obtain a certain speed. Using the throttle you can select to use more gas. In simple terms if you are flooring the pedal at 1900 RPM and "maintaining" 55 mph, If you down shift and "maintain" 55 mph at 2700 RPM with less pedal then this is proper RPM to be at.
Let the pedal decide, If you can travel the same speed with less pedal that's the RPM you should use imo.
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Old 06-30-2013, 09:20 AM   #48
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^^^This!^^^
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Old 06-30-2013, 09:28 AM   #49
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Originally Posted by 03 TJX View Post
I've always disliked 6 speeds - in whatever application. It's just gear clutter - too many gears, too much shifting.

There's a lot myths about fuel economy and number of gears. Most people think 6th gear of a six speed is necessarily taller than 5th gear of a five speed, which is obviously bunk. It depends on what gears they put in the transmission.

More gears is usually more efficient for an automatic but not for a stick, because shifts are inefficient and the more of them you have the less efficient you will be. This is why cars like Corvette are programmed to skip gears in order to avoid gas guzzler tax. Saab once did an extensive study and report and came to the same conclusion - for better fuel economy on a stick - skip gears.

The EPA tests have confirmed this repeatedly over the last several decades - both in the transition from 4 speeds to 5 speeds and the transition from 5 speeds to 6 speeds. All else equal fewer gears on a manual transmission gets better mileage. The Wrangler transition to 6 speed is an example - the 2004 five speed gets better mileage than the 2005 six speed - same 4.0L engine, same 3.07 rear axle ratio, just more shifting on the six speed. (The EPA test requires shifting through all available gears on a manual.)

This idea that more gears brings fuel economy is a powerful myth and manufacturers are now pretty much stuck with it.
The whole idea of more gears in a transmission is to keep the engine rpm as close to the center of the power band as possible. That keeps the engine operating as efficiently as possible.

Just because the majority of drivers can't (or won't) operate the vehicle in an efficient manner doesn't make this a "myth".
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Old 06-30-2013, 10:48 AM   #50
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What does the redline have to do with efficiency?

Nothing and I made no mention of a relation between redline and efficiency. Your statement "I'd run away,, run away!!" just make me chuckle.


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Originally Posted by Rubicondon53 View Post
It's a bargain we all make with our energy consumption every day.

side note: the idea of efficiency in relation to a Wrangler is, for the most part, laughable


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Originally Posted by Rubicondon53 View Post
You cannot tell me that you prefer to run your jeep at 70 mph in 4th gear at 2800 rpms, when operating in 5th at 2400 at 70 gets the same result with less energy expended.

I prefer to run my Jeep at 80 mph indicated and 3000 rpm indicated in 6th gear.


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Originally Posted by Rubicondon53 View Post
I haven't even gotten into the wear and tear on the engine... These motors are good for a quarter million miles, given they are normally operated at the bottom end of the torque band, 2100-2700 rpms... Run them constantly at 3000 rpms and up? Just take 75 to 100 thousand miles off of that quarter million.

^ unsupported hypothesis


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Do I know where the redline is?

If the mfg. was so worried about not exceeding 3000 rpm due to excessive engine wear, would they have marked the safe operation range at above 5000 rpm? No.


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I have no words...

You have plenty of words. Mostly opinions and few facts. Not that there's anything wrong with that.

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