Query re: mileage difference between 2WD and 4A

[goblues38]

The question: if you aren't triggering the second set of drivewheels, does leaving it in 4A have any effect on the mileage, and if it does, would you be so kind as to clue me in as to why?

Thanks, Jeds.

yes. about 1 mpg....if you never get the front hubs to lock up. the reason is, the center transfer case is engaged and sending power to the front diff. it is disconnected at the hubs. so you have a little extra drive line resistance. not much, but it is there.

 

[Oldfart]

Now you’ve called @Oldfart

he’s the resident mechanical friction expert

I firmly believe in lubing everything in sight, just for safety! I keep 3 of the 55 gallon drums on hand, just in case.

 

[amREADY]

I think it's been covered, but more components moving (to speed up, then slow down) with hubs engaged. As said, even under very modest acceleration, some power vectors to the front which adds to the hit.

I've found it is probably shy of 1 mpg to run in 4A. Lots of rain here and I use it in really heavy rain, but not light to moderate rain. I also use it on steeper roads, even if dry - saves the rear tires. And the steeper roads it provides a more planted feel.

I'm of the mind that whether you need it or not, you should use it about once a month. Not sure if that artefact from manual hubs carries over to these or not?

 

[TwizzleStix]

The mileage hit is less than 1 mpg for SURE. I’ve run mine in 4A for ~40,000 miles of the total of 55,000 on my 2018 802A. The previous gen raptors and F-150 4wd systems did NOT have the 4A mode. There is no valid reason to not run the new Raptor and/or F-150 in 4A all the time. That’s wtf it’s designed for.

 

[TwizzleStix]

yes. about 1 mpg....if you never get the front hubs to lock up. the reason is, the center transfer case is engaged and sending power to the front diff. it is disconnected at the hubs. so you have a little extra drive line resistance. not much, but it is there.

Sounds like you don’t understand the transfer case function. The front hubs are always locked in while in 4A, 4H, and 4L. The “auto” part is an electronic clutch inside the transfer case that applies torque to the already spinning front drive shaft, etc.

 

[goblues38]

Sounds like you don’t understand the transfer case function. The front hubs are always locked in while in 4A, 4H, and 4L. The “auto” part is an electronic clutch inside the transfer case that applies torque to the already spinning front drive shaft, etc.

I thought the hubs were engaging and dis engaging in that scenario? either way...it doesnt make much difference. @ the transfer case or @ the hubs...there is some part of the drive line that is still being driven

 

[onthebrake]

I run my '17 in 4A all the time. It really helps with even tire wear, that's for sure.

 

[TwizzleStix]

I thought the hubs were engaging and dis engaging in that scenario? either way...it doesnt make much difference. @ the transfer case or @ the hubs...there is some part of the drive line that is still being driven

Sorry go, but there is a huge difference. If you really don't know how something works, it's probably a good idea to not post about it.

 

[goblues38]

Sorry go, but there is a huge difference. If you really don't know how something works, it's probably a good idea to not post about it.

Ok Karen.

 

[LeadFootLarry]

I’ll add my 2 cents to this. After my TCCM took a dump and is awaiting replacement, the dealer said they had to “manually lock the front hubs” in the interim, and that I would experience lower MPG. To that tune, I have noticed about 1-1.5MPG decrease since they performed that service. Seems in line with what others are saying