Question about 4WD Auto mode

[bigoldthor]

So, I know we can theoretically leave the truck in 4WD Auto mode indefinitely. My F150s had this same feature. However, it seemed when I used 4A on the Fords, it dragged down fuel economy, like the torque converter was engaged but not powering or something like that. (I'm not a mechanical expert...know just enough to be dangerous.)

With the Ram, do you us 4A a lot, and does it seem to have any impact on fuel economy or anything else? Does anything "engage" but not run until the truck computer determines 4WD is needed? How well does it work in wet/slippery conditions in your experience?

 

[Reverse]

I have it on whenever the weather is nasty or roads are unpaved. Probably 30% of the time. I don't really notice a significant decrease in fuel economy.

4A works very well. It even kicks in when I use it on steep uphill paved roads. Just remember that for 4A (or the other two modes) to kick in, there always needs to be wheel slip (a difference in speed between front and rear). So maybe not so great to get you out of trouble if you're stuck in mud or snow already.

 

[Moe1962]

So, I know we can theoretically leave the truck in 4WD Auto mode indefinitely. My F150s had this same feature. However, it seemed when I used 4A on the Fords, it dragged down fuel economy, like the torque converter was engaged but not powering or something like that. (I'm not a mechanical expert...know just enough to be dangerous.)

With the Ram, do you us 4A a lot, and does it seem to have any impact on fuel economy or anything else? Does anything "engage" but not run until the truck computer determines 4WD is needed? How well does it work in wet/slippery conditions in your experience?

I use the feature when the roads are wet. I don't notice if anything engages, however, I haven't slipped using it. I have before in 2 wheel, the reason I use it exclusively on wet roads now. I have only seen a decrease in MPG somewhere between .5 and 1.5 on my 65 mile trip to work.

 

[SpeedyV]

With the Ram, do you us 4A a lot, and does it seem to have any impact on fuel economy or anything else? Does anything "engage" but not run until the truck computer determines 4WD is needed?

It does partially engage the system, so there is a parasitic loss to fuel economy—maybe 10% (ballpark). I use mine in inclement weather, but I haven't encountered enough slippery situations yet to evaluate its performance.

 

[bigoldthor]

65 mile commute?! Wow! I used to do 55 and that was bad enough, but it was mostly state roads and not much interstate.

 

[jdmartin]

Using constant 4wd auto locks the axles but keeps the transfer case disengaged unless you need it. So yes, there will be a fuel economy hit because you have more rolling mass friction loss. It's kind of like my old Nissan Titan, which always had the front axles locked (no 4wd auto mode) and so dragged fuel economy down somewhat.

Best practice is to only use 4wd auto when you need it.

As for how well does it work? Fantastic. I have used it a handful of times in snowy weather and it engaged seamlessly.

 

[Moe1962]

65 mile commute?! Wow! I used to do 55 and that was bad enough, but it was mostly state roads and not much interstate.

All back roads and two small towns to go thru. Only problem is it gets very dark and the deer crossing the roads. Glad these things have plenty of light. Not a bad drive when it's light out, no rain since you can step on it a little. Oh, that 65 miles is one way.

 

[Pyleketerson]

Humbling to be asking this question but how do you tell when it’s actually engaging? I’m almost through two winters up here in snowy WA state and have used it for countless miles, but if someone asked me how often it engaged I’d just have to shrug my shoulders. I honestly don’t know.

 

[jdmartin]

I don't think there is any good way to know. Because the front axles are already locked, I can't tell any difference when it engages/ disengages on mixed roads.

 

[Narg]

I'm a future RAM owner, but I can speak on terms of the current Silverado I have. In 4 Auto mode, the front may not be fully operating, but things are engaged. You can hear it spinning much of the time. It's most apparent on the highway, as when I accelerate the front axel does give audible feed back with a slight extra mechanical noise. And, yes I do see at least a tiny drop in MPG. So, unless needed I go with 2WD most of the time. If I am in 4 Auto, it's usually due to rain where the extra traction really makes a difference. My neck of the woods only gets ice/snow a couple weeks out of the year.

 

[bigoldthor]

Using constant 4wd auto locks the axles but keeps the transfer case disengaged unless you need it. So yes, there will be a fuel economy hit because you have more rolling mass friction loss. It's kind of like my old Nissan Titan, which always had the front axles locked (no 4wd auto mode) and so dragged fuel economy down somewhat.

Best practice is to only use 4wd auto when you need it.

As for how well does it work? Fantastic. I have used it a handful of times in snowy weather and it engaged seamlessly.

I'm a future RAM owner, but I can speak on terms of the current Silverado I have. In 4 Auto mode, the front may not be fully operating, but things are engaged. You can hear it spinning much of the time. It's most apparent on the highway, as when I accelerate the front axel does give audible feed back with a slight extra mechanical noise. And, yes I do see at least a tiny drop in MPG. So, unless needed I go with 2WD most of the time. If I am in 4 Auto, it's usually due to rain where the extra traction really makes a difference. My neck of the woods only gets ice/snow a couple weeks out of the year.

Yeah, that's kind of what I thought. Makes sense, and it seemed to work that way in the F150, as with the GM products it seems. Would be nice to know when it engages, like maybe an indicator light on the dash or something. Regardless, good to hear it works well.

And as with you guys and I'm sure most others, my practice has always been to leave it in 2A unless I think there is any legitimate chance of traction loss.

 

[Jus Cruisin]

I can feel the 4A when accelerating from a stop in the snow. You can feel the front end pulling and searching a little. I've clicked on only a few times since moving north. Really haven't had much snow (yay!) so far this winter.