4 High Issue
Posting Guru
Joined: Dec 2017
Posts: 1,441
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Many misinformed people here.
There is zero harm in engaging 4H at any speed so long as you are not spinning your rear wheels. There is no speed limit to how fast you can go in 4x4. The transfer case surely doesn’t care.
2017 trucks use a new type of transfer case which does have a clutch to smooth engagement and disengagement. When the hubs engage and spin up, there can be a clunk. Nothing is harmed. The clutch in the transfer case actually allows more leeway for the driver to be on the gas during engagement.
I frequently click in and out of 4x4 at interstate speeds if conditions warrant.
There is zero harm in engaging 4H at any speed so long as you are not spinning your rear wheels. There is no speed limit to how fast you can go in 4x4. The transfer case surely doesn’t care.
2017 trucks use a new type of transfer case which does have a clutch to smooth engagement and disengagement. When the hubs engage and spin up, there can be a clunk. Nothing is harmed. The clutch in the transfer case actually allows more leeway for the driver to be on the gas during engagement.
I frequently click in and out of 4x4 at interstate speeds if conditions warrant.
That being said, I just manually locked my hubs, they won't be unlocked again until March.
Hotshot
Joined: Apr 2013
Posts: 10,118
Likes: 650
From: NH
The workshop manual sheds a fair amount of light on the 4x4 system in this truck. It has some substantial differences compared to the previous system.
The clutch (electro-mechanical) is the biggest difference. The benefits are smoother engagement and disengagement and less shock-loading of components. The disadvantage is another possible failure point.
One cool thing is that the system takes into account steering angle and wheelspeeds. Although the manual doesn't say specifically, I'd say it is unlikely the system will attempt to engage the front axle with spinning rear wheels or a hard left or right steering angle.
The vaccum controlled auto locking hubs are different this year as well...they no longer are pulse-vacuum controlled but are now constant vacuum hublocks. They also no longer require vacuum to disengage. Previously, a lower level of vacuum was used to disengage the hubs. When 2WD is commanded by the dashboard switch, vacuum is cut and vented by the vacuum control solenoid immediately, and spring pressure that the vacuum normally overcomes causes the hubs to disengage.
Another cool thing is that the system *can* detect when the hubs do not engage, despite there being no sensors in the wheel hubs themselves. Basically the system looks at individual wheelspeeds, the steering angle, and the position of the 4x4 switch. If the truck is supposed to be in 4x4, the front wheel speeds will be a set speed at any amount of steering angle...and this speed will vary from the individual speeds of the front wheels while in 2WD. The vacuum solenoid control and transfer case can both set DTC's for failures to work properly. If no DTCs are registered but the front wheel speeds do not match up...the the system assumes a hub lock failure and sets a DTC for it. Very cool even if not specific!
The clutch (electro-mechanical) is the biggest difference. The benefits are smoother engagement and disengagement and less shock-loading of components. The disadvantage is another possible failure point.
One cool thing is that the system takes into account steering angle and wheelspeeds. Although the manual doesn't say specifically, I'd say it is unlikely the system will attempt to engage the front axle with spinning rear wheels or a hard left or right steering angle.
The vaccum controlled auto locking hubs are different this year as well...they no longer are pulse-vacuum controlled but are now constant vacuum hublocks. They also no longer require vacuum to disengage. Previously, a lower level of vacuum was used to disengage the hubs. When 2WD is commanded by the dashboard switch, vacuum is cut and vented by the vacuum control solenoid immediately, and spring pressure that the vacuum normally overcomes causes the hubs to disengage.
Another cool thing is that the system *can* detect when the hubs do not engage, despite there being no sensors in the wheel hubs themselves. Basically the system looks at individual wheelspeeds, the steering angle, and the position of the 4x4 switch. If the truck is supposed to be in 4x4, the front wheel speeds will be a set speed at any amount of steering angle...and this speed will vary from the individual speeds of the front wheels while in 2WD. The vacuum solenoid control and transfer case can both set DTC's for failures to work properly. If no DTCs are registered but the front wheel speeds do not match up...the the system assumes a hub lock failure and sets a DTC for it. Very cool even if not specific!
New User
Joined: Feb 2018
Posts: 11
Likes: 0
Yep my 2017 has a gremlin living in its transfercase to
I am disappointed my dealership replaced the driveshaft twice and the transfer case as well truck has 3000 miles. It also pops or clunks at slow speeds when I stop or start out a lot of the time. Sounds like right under the driver seat. It sounds bad. Anyone else with the same on 2017 f350 6.2 gas
New User
Joined: Feb 2018
Posts: 11
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2017 f350 4 High Issue
this March my dealer found filings in the transfercase oil replaced the transfer case with new still makes lots of noise in four wheel drive. On snow covered roads on the way to a wrestling tournament I kicked the four wheel drive out I was not sure I would make it there. This noise along with the low speed click and poping noises COMPLETELY NEEDS FORD UPGRADE. I like the truck other than this
New User
Joined: Feb 2018
Posts: 11
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4 high have excessive noise.
The dealer has replaced the transfer case at 2800 miles it was full of filings the oil gas full of material they. Screened the oil and showed me it. Thing is I think the new one is just as bad
Hotshot
Joined: Apr 2013
Posts: 10,118
Likes: 650
From: NH
Sounds like the OP has a series problem.
New User
Joined: Feb 2018
Posts: 11
Likes: 0
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