I have read on here how some people run Auto 4wd year round or on wet pavement. I am in MN and we have snow on the ground and there are patches of ice out there. Heck some lesser traveled gravel roads are ice covered. So, I switched to 4A and figured I would leave it there all winter. I am coming from a Subaru WRX and a Yukon Denali both which were AWD so I am used to AWD. I get that Ford locks the hubs in 4A and locks in the transfer case as needed. Tonight I was making a sharp turn on pavement and the front end bound up and there was a loud pop. Like what one would expect in 4H. I checked to make sure I wasn't in 4H but the dial and dash showed 4A.

So, any ideas? I am not overly concerned as far as warranty being it is a 2018 with 35K. I also have an extended warranty to 150K. I bought the truck used in April so this is my first winter with it and first Ford. So just checking.

 

Interesting.
Was the bind feeling the same as you would experience if in 4x4 mode? Not sure if that is what you meant in your statement, or if you meant the pop was like a 4x4 sound.

I can't figure out what the popping sound would be. The binding makes sense per your description, but not while in 4a. That is a head scratcher.

Does it seem to engage/disengage like it would normall...shift on the fly is still seamless and no difference in the noises when a shift occurs?
I haven't used 4a in a long time but it never does what you described.

I did engage it for a few minutes just over the weekend on a dry roadway and if not for the slight change in noise, I would not know I shifted to 4a mode.

 

That is why I thought it was strange. For the record. I have owned many 4wd vehicles over the years as well as a few AWD. Heck even a 4wd tractor. I was on dry pavement and it felt like the front end binding like I was in 4H when making a sharp right turn like I was stepping on the brake and slowing, then there was an audible pop and it felt like I took my foot off the brake or the binding released. My tractor feels the same way in 4wd on dry pavement. Not that I make a habit of that but I do run 4wd when carrying a heavy load in the front end loader. I make sharp turns all the time on dry pavement in 2wd in the truck and have never felt this.

Like I mentioned I am new to Ford and got this truck in April so the sounds it has been making are all what I would consider normal. Pretty quite in 2wd and nothing strange. A slight hum maybe in 4A but that is all I have ever noticed which could be explained by additional driveline motion. Shift on the fly to 4H seems fine as well as normal shifting to 4L the one time I tried it. When I was making the turn it shouldn't have detected slip and kicked in the 4wd. I was going slow, 10 MPH maybe. In fact I was leaving a Boy Scout Camp on the way up a hill on what I would describe switch backs. I checked to see if the Diff Lock was enabled but it wasn't and it felt like front end binding and the pop in the front end. It wasn't a big shift in grade where a tire lost traction like I said or I had a tire rub.

Being a used truck and I have no idea what the previous owner did, a limited slip front diff of some sort? I have driven Hummers in the military and it felt like that. Like a locked front end. If that is the case I should be able to reproduce if needed in my driveway. I kind of doubt that but this just seems strange. I also have read where people are saying that they just leave their trucks in 4A all the time and they must not be experiencing this.

I was going to take it in for an oil change before heading up north for deer camp but I might just wait until after and have them go over the 4wd if I still have an issue. I have read of IWE issues but I don't think this explains it. Heck people disconnect them at times so they would be locked in all the time that way on the front. I have also owned GM trucks with their Auto 4wd which is very similar to what I understand Ford does and they have never bound up making sharp turns in Auto 4WD mode on drive payment.

 

I have been using Auto 4WD more on dry and snowy roads. I haven't been able to replicate the feel of 'lockup" again. I kind of am wondering if it was a tire rub. I do have a leveling kit but also have bigger wheels. When it did this I was at nearly full lock and the road kind of had a strange grade transition. I drove the same road about a week ago and there was nothing but I might have hit the corner at a slightly different angle and/or speed. I hadn't been back to the area for a while because it was closed due to Covid.

 

Thanks for the follow. And here is a follow up note:

Literature say both differentials remain open while in 4A, so this leaves only the transaxle to bind. Could be an errant condition in which the system had the front driveline at full clutch pressure when you were getting good traction.

I'd verify that the system disengages the rear diff lock when switching into 4A. Don't see anything saying it does, but it should.

Did you make this turn shortly after starting the truck? Wondering if you could have had the rear diff lock on, had just switched 4A on, and the rear diff was slow to release.

 

I use 4A anytime it rains and on occasion making a slow sharp turn the front end bind.

 

As I mentioned in the earlier posts a few months back. I was at a scout meeting. We were still in the scout camp and it is a long hill going up from down near the river up the bluff. So, had a just started the truck? Yeah it was pretty soon after start. For sure not up to operating temp and what driving I did would have been at 15MPH or less as we were still on Scout Camp Property. While I had driven there at 65-70, I was parked there for say 90 minutes or so. Not sure how much it would have cooled off but it was fall so not a hot summer day. Speeds were slow enough that the rear diff lock could have been still locked up if I had it in that mode but I doubt I did. I think I have only turned it on once or twice just playing with how it works when pulling our camper (straight line) on grass.

When you say if it disengages rear diff lock in 4A are you saying that in 4A it wouldn't work at all no matter if at slow speeds? I know it works in 2WD at slow speeds but disables at what 25 or 30 MPH? Something like that. Not sure I have messed with it in 4A as I mentioned I really haven't messed with it at all.

 

If I am not mistaken, the 4wd engages for the first few minutes after a start to get all the parts warmed up. I think I read it on this forum but can't find it with the search function. With the cooler weather gong up hill slow it might have still been in 4WD at the time. Now I know someone will correct me if I miss spoke. Please do.

 

You're mostly right. 4wd doesn't engage thru the transfer case, just the IWEs engage for a determined distance to warm up front diff. The newer trucks do it on every key cycle.
That said, it's on the 2020 on back. I've not much info on the 2021, other than it's a electromagnetic IWE, opposed to vacuum.

 

Just the IWEs engage, not the transfer case. I believe it is a certain distance they stay engaged, something like a couple of miles.