Rumbling noise on turning 2017 exp LTD EL

[Yupster Dog]

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.

My 02 has the AWD and no 2WD. But it doesn't matter because no unlocking hubs. Everything spins 100% of the time. There is a mod (brown wire mod) to stop the AWD and make 2WD but even then no unlocking hubs so everything is still spinning. Even with that and always having 400lbs gear and tools I still get 14 mpg

 

[LokiWolf]

My 02 has the AWD and no 2WD. But it doesn't matter because no unlocking hubs. Everything spins 100% of the time. There is a mod (brown wire mod) to stop the AWD and make 2WD but even then no unlocking hubs so everything is still spinning. Even with that and always having 400lbs gear and tools I still get 14 mpg

Thanks YD! I couldn’t remember the year. I had a SCREW 150 back then, didn’t pay much attention to the Expy back then.


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[JExpedition07]

I can supply info about 07-14. The 07-14 Expedition uses the BorgWarner TOD (Torque on Demand) transfer case 4WD system. In 2H the hubs receive vacuum and disengage. In 4A hubs are engaged and the T-case has a microprocessor that can sense and even predict slippage before it occurrs. In winter 4A reacts so fast my 2007 doesn’t even spin the rear wheels, so I’m guessing it sends some static power all the time in 4A or does it faster than our brain can process it. The front diff spins and hubs spin in 4A so there is some extra drag. I only notice about a 0.5 MPG drop in 4A vs 2H.

 

[LokiWolf]

I can supply info about 07-14. The 07-14 Expedition uses the BorgWarner TOD (Torque on Demand) transfer case 4WD system. In 2H the hubs receive vacuum and disengage. In 4A hubs are engaged and the T-case has a microprocessor that can sense and even predict slippage before it occurrs. In winter 4A reacts so fast my 2007 doesn’t even spin the rear wheels, so I’m guessing it sends some static power all the time in 4A or does it faster than our brain can process it. The front diff spins and hubs spin in 4A so there is some extra drag. I only notice about a 0.5 MPG drop in 4A vs 2H.

Thanks J07!

I almost tagged you in my earlier post. I was hoping you would come along. You were the one that made me go out and learn the system on my previous 2 Expeditions. Need to go research my 2020, and see what is different.

I definitely have a similar impression of 4A. It reacts QUICK. Our Limited 2020 doesn’t even have the 4H option, just 2H, 4A, and 4L.


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[07navi]

Thanks J07!

I almost tagged you in my earlier post. I was hoping you would come along. You were the one that made me go out and learn the system on my previous 2 Expeditions. Need to go research my 2020, and see what is different.

I definitely have a similar impression of 4A. It reacts QUICKly. Our Limited 2020 doesn’t even have the 4H option, just 2H, 4A, and 4L.


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Probably because it's not a true off road vehicle and they figure this is good enough and they don't have to worry about people breaking parts because they made a sharp turn on the highway. I can see the whole thing.

 

[LokiWolf]

I can co firm first hand that the half shafts up front spin while In 2WD. Plenty of research and science to prove it and if I have to I’ll go video it happening on my vehicle so you can both shut the **** up, you are both annoying as hell know it alls

And you have reading comprehension issues. I told you why it spins...

If it is actually spinning full speed your hubs aren’t unlocking.


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[07navi]

And you have reading comprehension issues. I told you why it spins...

If it is actually spinning full speed your hubs aren’t unlocking.


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The axles were spinning extremely slowly in that video due to clutch drag but it might have just been that truck and if not it means nothing because it's just immeasurable clutch drag. I could almost read the tag on the axle it was spinning so slowly.

 

[Plati]

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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Quality response as expected. Thank You. I guess I knew it had that in the owners manual (even my 2014) but I was hoping for some actual data about "how much". Still appreciate the effort.

So ... here is what I might have said in response to that mpg/power issue. After 21 years with 3 Expy's that have 4A and 391,000 Expy miles under my belt .... and after I have driven most of those miles in 4A and some of those miles in 2H ... my own personal experience is that there is not much if any discernable difference in mpg and or "power" between the two. Of course I may not be the most capable person to sense any power difference but I have actually run several test drives to determine if there is a noticeable difference in mpg and do not recall ever reading a difference on a repeatable basis. That is not to say there isn't a difference, just that my testing regimen did not indicate a difference in mpg. My suspicion is that 2H will give you better mpg but such a small delta that for all intents and purposes there is no difference. I'm not aware of any testing that shows the magnitude of any difference or under what driving conditions such a difference would occur. Since I feel safer staying in 4A for that situation where that might provide improved road traction and my firm belief that there is only a minimal improvement in mpg, I choose to leave it in 4A most of the time. I have been able to confirm situations where 4A keeps the rear wheels from spinning (vs 2H) in situations where you would not prefer that to happen. I've put the vast majority of my 391K miles in 4A and have not had any drive train parts break yet. Small sample but thats what I've found.

and thats just my experience is all

 

[LokiWolf]

The axles were spinning extremely slowly in that video due to clutch drag but it might have just been that truck and if not it means nothing because it's just immeasurable clutch drag. I could almost read the tag on the axle it was spinning so slowly.

I honestly don’t believe it is clutch drag.

In my old CJ7 with manual locking hubs and an old school manual lever driven transfer case, they would spin slowly at high way speed and no where near the speed the wheel was going. It was because even great greased bearings would still transfer enough energy to spin them a little.


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[LokiWolf]

Quality response as expected. Thank You. I guess I knew it had that in the owners manual (even my 2014) but I was hoping for some actual data about "how much". Still appreciate the effort.

So ... here is what I might have said in response to that mpg/power issue. After 21 years with 3 Expy's that have 4A and 391,000 Expy miles under my belt .... and after I have driven most of those miles in 4A and some of those miles in 2H ... my own personal experience is that there is not much if any discernable difference in mpg and or "power" between the two. Of course I may not be the most capable person to sense any power difference but I have actually run several test drives to determine if there is a noticeable difference in mpg and do not recall ever reading a difference on a repeatable basis. That is not to say there isn't a difference, just that my testing regimen did not indicate a difference in mpg. My suspicion is that 2H will give you better mpg but such a small delta that for all intents and purposes there is no difference. I'm not aware of any testing that shows the magnitude of any difference or under what driving conditions such a difference would occur. Since I feel safer staying in 4A for that situation where that might provide improved road traction and my firm belief that there is only a minimal improvement in mpg, I choose to leave it in 4A most of the time. I have been able to confirm situations where 4A keeps the rear wheels from spinning (vs 2H) in situations where you would not prefer that to happen. I've put the vast majority of my 391K miles in 4A and have not had any drive train parts break yet. Small sample but thats what I've found.

and thats just my experience is all

Excellent real world experience! Awesome stuff.

In adverse conditions, I definitely engage 4A, and agree it definitely helps with Traction.


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