Help with 4x4 auto

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Plati

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Both my 2003 and my 2014 I drive in 4A 99% of the time. I have no reason to drive in 2H to save gas which is the reason people normally give to do that. I do put it in 2H sometimes just for the heck of it. I cannot tell any difference in normal driving and I never have heard any noises like you mention. Same with the 1999 I previously owned. In special situations I also use 4H and 4L. Thats 400,000 miles of experience in 3 Expys.

Dealer telling you not to use 4A on dry pavement ... either there is a misunderstanding or he is way off wrong and does not know what he's talking about.

My understanding is that the front is "engaged" (as you phrase it) once ... When you turn dial to 4A and stays that way. Power is applied as required by the Transfer Case in 1% increments from then on, the 4WD doesn't connect and disconnect.
 
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Trainmaster

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The A4's fine to use all the time, according to the owners' manual and many years experience. I can tell when I have it selected but there's no clunking, grinding or chattering in turns.

If yours is misbehaving, there's something wrong with it.
 

vincentrose

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Both my 2003 and my 2014 I drive in 4A 99% of the time. I have no reason to drive in 2H to save gas which is the reason people normally give to do that. I do put it in 2H sometimes just for the heck of it. I cannot tell any difference in normal driving and I never have heard any noises like you mention. Same with the 1999 I previously owned. In special situations I also use 4H and 4L. Thats 400,000 miles of experience in 3 Expys.

Dealer telling you not to use 4A on dry pavement ... either there is a misunderstanding or he is way off wrong and does not know what he's talking about.

My understanding is that the front is "engaged" (as you phrase it) once ... When you turn dial to 4A and stays that way. Power is applied as required by the Transfer Case in 1% increments from then on, the 4WD doesn't connect and disconnect.


Yes you are correct about the front being "engaged" but while the front is engaged, the front axle shafts, the front differential and the front driveshaft are all engaged to the front wheels and turning. This is mechanical resistance, which uses energy, and on dry pavement it is unnecessary, and will use more fuel in doing so, causing your mileage to drop 1-2 mpg, and of course unnecessary wear and tear on these components as well. Which is why there is a front wheel hubs disconnect on the IWE's so that the front driveline doesn't have to rotate when its not necessary and thus saving that extra fuel by not having that unnecessary mechanical resistance.
 

Plati

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Yes you are correct about the front being "engaged" but while the front is engaged, the front axle shafts, the front differential and the front driveshaft are all engaged to the front wheels and turning. This is mechanical resistance, which uses energy, and on dry pavement it is unnecessary, and will use more fuel in doing so, causing your mileage to drop 1-2 mpg, and of course unnecessary wear and tear on these components as well. Which is why there is a front wheel hubs disconnect on the IWE's so that the front driveline doesn't have to rotate when its not necessary and thus saving that extra fuel by not having that unnecessary mechanical resistance.
Yes. Pretty much totally agree & you mention the second and third reasons to run in 2H. I have done some unscientific tests and my experimentation plus my thought process tells me it is more likely to be under 1 MPG but I can't stand behind that with other than gut feel. I also don't think the wear would be substantial, also gut feel. I want the traction for unexpected rainstorms that I encounter without remembering and switching so I just leave it in 4A taking the economic hit. Potential safety over economy. Good points you have!

So when in 2H .. front wheels are disconnected from side shafts spinning freely along road and everything in front of Transfer Case to wheels is also not spinning? Not sure I knew that last part. But it makes sense that Transfer Case will loosen up and not send power to front in 2H. Thanks

I just drove 1500 miles down East Coast in 2H cause when I left home I thought I would try it. Its zactly like 4A did not notice any difference. 17.5 MPG. I think I'll ManUp run in 2H and switch to 4A as needed?
 
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07navi

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vince is right in all areas. It is zero safer on dry pavement and your front diff, u-joints, t-case are working needlessly. It's a lose/lose scenario. It's not even safer on wet pavement unless maybe you floor it at stoplights in the rain.
 

vincentrose

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So when in 2H .. front wheels are disconnected from side shafts spinning freely along road and everything in front of Transfer Case to wheels is also not spinning? Not sure I knew that last part. But it makes sense that Transfer Case will loosen up and not send power to front in 2H. Thanks

I just drove 1500 miles down East Coast in 2H cause when I left home I thought I would try it. Its zactly like 4A did not notice any difference. 17.5 MPG. I think I'll ManUp run in 2H and switch to 4A as needed?

Yes, you are correct, the IWE's (Integrated Wheel Ends) are vacuum controlled and disconnect the wheel hubs from the half shafts, and thus the Half Shafts, Diff, and driveshaft doesn't rotate while in 2H mode
 

07navi

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Right again, there is
Yes, you are correct, the IWE's (Integrated Wheel Ends) are vacuum controlled and disconnect the wheel hubs from the half shafts, and thus the Half Shafts, Diff, and driveshaft doesn't rotate while in 2H mode
Right again, there is no reason for anyone to drive in 4wd auto unless the road is snowy, icy, or some other rarely needed occasion.
 

lbv150

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When my wife drives in or right after a winter storm, I just tell her in put it in 4A....much easier for her and nothing will get screwed up on the truck. I never use 4A as I know when to use and not to use 4H. I would prefer Warn manual locking hubs and a lever 2H N 4H 4L like in my pickups. No need for 4A...
 
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Plati

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Right again, there is

Right again, there is no reason for anyone to drive in 4wd auto unless the road is snowy, icy, or some other rarely needed occasion.
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