When I drive in 2H mode, I sometimes heard the tire spin noise if accelerated fast from a stop, especially when turning. So, I'd like to stick with 4A mode. But not sure if there's a big difference on MPG? Has anyone tested on that?

Thanks,

 

A while back, I told a buddy with a Lariat, who was complaining about mpg in his 3.5 to switch to 2wd, from 4A which he had used exclusively. So he did and says it gets him 1-2mpg better than 4A.

My 5.0 still gets better mpg than his...

 

Not as big as the switch from Eco to Normal. At the slight sight of rain or wet road my truck goes into 4A. I have not noticed any major MPG drops on trip computer and on hand calculation by running 4A for longer periods of time. Running in Eco vs. Normal (no matter how hard I try to be light footed, that throttle is WAAAAY to sensitive, worse than my BMW in Sport mode), I see 1-2 MPG improvement. So if you are worried about MPG, don't start at the 4A vs 2H.

 

I have not noticed any significant difference (maybe 1-2 MPG) between 4A and 2H. I used to have to be very light on the throttle when the roads are wet because of rear wheel spin problems. I think a lot of that problem was due to the tires I had at the time. They were the "stock" Hankook AT tires. The only way to really NOT have wheelspin problems in the wet was to put my truck in 4A. Now I've got Falken Wildpeak AT3W tires on and I have to get somewhat aggressive with the throttle to spin the tires in the wet. These tires are a bit "stickier" than the Hankook tires and I've noticed a slight decrease in MPG but it's not all that significant, probably less than switching to 4A.

About the only thing I would caution people about with 4A is using a LOT of throttle while in this mode. 4A is very tolerant of slip between front and rear drive shafts but... when you apply much throttle, the TC is going to command the clutch plates to apply harder, which makes the TC less tolerant of slip because it is near full lockup and would behave as if it is in 4H mode during that time. IOW: if you're in 4A, accelerate HARD only in a straight or nearly straight line. As long as you remember that simple limitation, your TC clutch pack will thank you and you'll be able to drive in 4A most of the time if you desire to.

Interesting point: a few weeks back, we had a very wet weekend where I'm at and I decided to find out how much power it would take to spin the wheels with the new tires. It took quite a bit to do it and when the rear tires lost grip (under lots of throttle) the truck fishtailed very abruptly. I don't normally drive that aggressively so I have very little concern about spinning the tires in my normal every-day driving even when the roads are wet. I haven't tried these tires in the snow or on icy roads yet... but I hope to this winter. Should be fun!

 

My 22 Reg Cab short bed with the 5.0 has a little under 3,000 miles,last tank i got right at 22 mpg,,,,,75 % hiway miles.

 

My '22 lariat has no hub disconnects on the front axle. so the front driveshaft and transfer case chain are spinning no matter 2H or not. I doubt you see any difference if your truck is configured this way.

Now my '16 had the disconnects up front.. maybe better for mpg in 2H.. but vacuum issues as well..

 

Doiii when I floor it my tires make a tire spin noise

 

I just drove from TN to MO, SD, ND, ID, WA to UT in 2WD. While I was in Salt lake I had an IWE fail, so I had it replaced. When I left Salt Lake heading to CO my other one failed, so I put it in 4A and the noise stopped. I then went on to NM, TX, AR, then TN. On the first part of the trip I got 18.4 MPG. The next part of the trip that was not as many mountains I got 18.5 MPG. So in my option it really does not matter.

(EDIT) This was in a 2020 Expedition. So the old style IWE's.

 

Thank you everyone for your replies! I monitored the "power" view (sorry, forgot what the exact name it is, the one that shows if it's engine or battery that was driving the vehicle) in last a few days and noticed that when in 4A mode, 4WD was involved during starting up or high drive power was needed. When the vehicle was in cruise mode, it switched to 2WD.

Based on that observation, it does make sense that during long distance trip, the MPG difference is small because most of the time it will be in cruise mode. But I'm not sure how the diff is during city driving, when I'll 4A more than during long distance driving.

 

And I couldn’t detect more than a rounding error of difference on my 2020 3.5 eco SCREW.

One of my current trucks, the 22 supercharged screw, had no front IWE’s so I suspect no difference there at all, but haven’t ever checked, as it needs 4auto with 775hp