Rumbling noise on turning 2017 exp LTD EL

[LokiWolf]

Clarity:

4A does have worse MPG than 2WD. That has been well documented.

Everything does not spin in 2WD.

Both of the above are fact. You can feel the difference, just in the amount of throttle needed to move the vehicle. My wife even noticed it.

You don’t have less power in 4A, but you do have increased driveline loss, because there is more spinning inertia. So power to the wheels is decreased.

On a hard launch or slippery surface that is negated by the fact that you have more traction, and under slippery conditions, more of the actual engine power is equating to forward motion.



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[Sunflowergirl]

Clarity:

4A does have worse MPG than 2WD. That has been well documented.

Everything does not spin in 2WD.

Both of the above are fact. You can feel the difference, just in the amount of throttle needed to move the vehicle. My wife even noticed it.

You don’t have less power in 4A, but you do have increased driveline loss, because there is more spinning inertia. So power to the wheels is decreased.

On a hard launch or slippery surface that is negated by the fact that you have more traction, and under slippery conditions, more of the actual engine power is equating to forward motion.



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******* Christ here we go again. You obviously haven’t seen the video of the raptor in 2WD with the half shafts still rotating eventhough there is no power being sent to them in 2WD. You two clowns really make this forum unenjoyable

 

[07navi]

Clarity:

4A does have worse MPG than 2WD. That has been well documented.

Everything does not spin in 2WD.

Both of the above are fact. You can feel the difference, just in the amount of throttle needed to move the vehicle. My wife even noticed it.

You don’t have less power in 4A, but you do have increased driveline loss, because there is more spinning inertia. So power to the wheels is decreased.

On a hard launch or slippery surface that is negated by the fact that you have more traction, and under slippery conditions, more of the actual engine power is equating to forward motion.



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By less power I mean less acceleration, of course the engine power remains the same.

 

[LokiWolf]

By less power I mean less acceleration, of course the engine power remains the same.

Power and acceleration are 2 different things. Acceleration brings traction in to play. So 4A can actually increase acceleration under high load(hard launch) or low traction(wet, snow, gravel) situations.

Available power to the wheels is decreased by having 4A engaged vs 2WD on 3rd Gen Expeditions. Honestly haven’t researched the 4th Gens systems enough to make comment on those.


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[07navi]

Power and acceleration are 2 different things. Acceleration brings traction in to play. So 4A can actually increase acceleration under high load(hard launch) or low traction(wet, snow, gravel) situations.

Available power to the wheels is decreased by having 4A engaged vs 2WD on 3rd Gen Expeditions. Honestly haven’t researched the 4th Gens systems enough to make comment on those.


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But that's a no brainer and I never said anything about those conditions.

 

[LokiWolf]

But that's a no brainer and I never said anything about those conditions.

10-4. Just clarifying. I like to be clear and concise and blanket statements rarely are cut and dry. Hence my clarity. For some it is a no brainer...


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[07navi]

10-4. Just clarifying. I like to be clear and concise and blanket statements rarely are cut and dry. Hence my clarity. For some it is a no brainer...


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OK, one more thing; while that video showed the front drive train of the Raptor slowly turning in 2WD I think it might just be that truck or they have fixed that since then since clutches aren't supposed to drag.
One more thing; someone earlier said they always keep it in auto while roads are wet but that does nothing unless you floor it at stoplights and are in a hurry. Auto is actually only beneficial in rare instances and shouldn't be used otherwise.

 

[Plati]

OK, one more thing; while that video showed the front drive train of the Raptor slowly turning in 2WD I think it might just be that truck or they have fixed that since then since clutches aren't supposed to drag.
One more thing; someone earlier said they always keep it in auto while roads are wet but that does nothing unless you floor it at stoplights and are in a hurry. Auto is actually only beneficial in rare instances and shouldn't be used otherwise.

MsNavi
there's no point in debating anything with you, you are a Troll and just like to argue
no amount of information would change your stated "fake opinions"
which exist merely to annoy others

MrLoki ... can you point me to where its documented? ... please?
your quote: "4A does have worse MPG than 2WD. That has been well documented"
I've never seen it documented other than someone on a Forum stating it as fact
and I guess where you saw it documented, what is the magnitude? less than 1 mpg?
and under what driving conditions was it demonstrated?

 

[07navi]

MsNavi
there's no point in debating anything with you, you are a Troll and just like to argue
no amount of information would change your stated "fake opinions"
which exist merely to annoy others

MrLoki ... can you point me to where its documented? ... please?
your quote: "4A does have worse MPG than 2WD. That has been well documented"
I've never seen it documented other than someone on a Forum stating it as fact
and I guess where you saw it documented, what is the magnitude? less than 1 mpg?
and under what driving conditions was it demonstrated?

Actually I just try to help everyone by using my extensive mechanical background and Lokiwolf is right. I have seen 2 mpg loss many times elsewhere. Don't be a stickler.

 

[LokiWolf]

MrLoki ... can you point me to where its documented? ... please?
your quote: "4A does have worse MPG than 2WD. That has been well documented"

How about page 166 of the 2017 Manual:

The Control Trac[emoji2400] system functions in four modes:
• 2H delivers power to the rear wheels only. The information display will momentarily display 2H when this mode is selected. This mode is appropriate for normal on-road driving on dry pavement and provides the best fuel economy.
• 4A provides electronic control four-wheel drive with power delivered to all four wheels, as required, for increased traction. The information display will display 4A when this mode is selected. This mode is appropriate for all on-road driving conditions, such as dry road surfaces, wet pavement, snow, or gravel.
• 4H provides electronically locked four-wheel drive power to front and rear wheels. The information display will display 4H when this mode is selected. This mode is not recommended for use on dry pavement. This mode is only intended for severe winter or off-road conditions, such as deep snow, ice or shallow sand.
• 4L provides electronically locked four-wheel drive when extra power at reduced speeds is required. The information display will display 4L when this mode is selected. This mode is not recommended for use on dry pavement. Use this mode for off-road low-speed operation or when extra power is required, such as climbing steep grades, going through deep sand or pulling a boat out of the water.

There was a year of the Expedition, honestly can’t remember what year, cause I didn’t own one back then that only had 4A, no 2WD. A coworkers wife had one, and they always complained about the terrible MPG. It was talked about a lot at one point. It just makes sense that it would lower MPG.

Let’s go over the 15-17 4WD and what is in play in each mode as I understand it.

The changes in this system happens in 2 places, the front hubs and the center Diff(Transfer case).

2H - Front Hubs unlocked - Transfer case sends zero power to the front Dif. There will still be some spinning of the front half shafts and driveshaft because even greased hubs and bearings will transfer some inertia.

4A - Front Hubs locked - Transfer case sends zero power to the front Diff unless there is slippage detected by wheel speed sensors. The front wheels are now directly connected to the front half shafts, front Diff, and front driveshaft. It takes added energy(drag) to move those components.

4H - Front Hubs Locked - Transfer case sends a more fixed percentage of power forward to the Front Diff, more like a classic 4WD system. Only should be used off road and in conditions like snow.

4L - Front Hubs Locked - Tranfer case engages lower gearing an sends a more fixed percentage of power forward to the front dif.

Hope that helps...




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