4x4 Question??
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Freshman User
Joined: Sep 2005
Posts: 25
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4x4 Question??
Ok, could someone educate me on how the auto shift-on-the-fly works on my 2005 superduty. I get that in auto the hubs are vacuum actuated and in lock you over-ride the vacuum and lock the hub. When the truck is placed in 4x4 (hi or low) the truck is hard to steer like it has a locker in the front end. For this reason I figured if the hubs were placed in lock it would be hard to steer as well, but this isn't the case. Does the vacuum actuatation also lock the differential as well?? I'm confused 
Tuned
Joined: Feb 2009
Posts: 484
Likes: 6
From: Alberta
My truck is a 2004. With the hubs set to auto I just turn the switch to 4 high while the truck is moving and it engages the transfer case and hubs. To engage 4 low you must be stopped and in neutral. Note that it might take a bit of fiddling. Tried mine today, stopped, neutral, switch to 4 low from 4 high - no go, drove ahead a bit, back to neutral and stopped and it went into 4 low and the instrument panel lit up the low range. To go out of 4 low, stop, neutral and switch to 4 high or 2 high.
I suspect the lock feature for the hubs is if the auto hub feature screws up you can switch manually. I would recommend turning both hubs to the same setting!
Being hard to turn, I suspect you may have been on dry pavement or on a surface that gave you good traction. 4x4's are not happy on dry pavement and really fight you when you turn sharp because the wheels can't slip easy like on mud, snow or sand.
Other folks here may have some better advice.
I suspect the lock feature for the hubs is if the auto hub feature screws up you can switch manually. I would recommend turning both hubs to the same setting!
Being hard to turn, I suspect you may have been on dry pavement or on a surface that gave you good traction. 4x4's are not happy on dry pavement and really fight you when you turn sharp because the wheels can't slip easy like on mud, snow or sand.
Other folks here may have some better advice.
Super Moderator
Joined: Oct 2005
Posts: 24,308
Likes: 42
From: SW Virginia
What you are experiencing is commonly referred to as "binding". It happens mostly when on dry surfaces or those with reasonably good traction. You have power directed to the front axle and when you turn the wheels, you also have the rear wheels trying to propel the truck forward. As the truck tries to continue forward and the front wheels are turned under power, you get a bucking or jerking type of sensation. The fornt and rear are locked and the power division is 50/50 so there is no provision for "slip" in the system. Unlike an all-wheel drive car or SUV that has constant all-wheel drive, there is no viscous coupling in the transfer case that allows torque differentiation between front and rear.
Postmaster
Joined: Jan 2005
Posts: 4,424
Likes: 12
From: BC Canada
Using 4 low, the manual recomends being stopped and transmission in neutral to shift. Also, it recomends manually locking hubs for 4 low. As for shifting in and out of 4 Hi, just like a manual t case, hubs dont always instantly lock in, t cases dont always shift just right, you have to shift and then unload the drive train, release pressure on accelerator, decelerate a bit or speed up a bit. This way things slide in and out of gear, hubs lock and un lock. If you are on dry pavement, good traction, sometimes things will stay locked until this driveline pressure is relieved. This is where a manual t case seems better becuase you can feel what the tcase is doing. Same tricks apply with auto tcase but you have to feel it in or out of gear, hubs too.
