I thought I remembered a topic about this, but I can't find it via search.

Whenever I switch into 4A there is a noticeable difference in vibration, sound, etc. Switching it back to 2WD and it goes away.

It is constant and more pronounced when you are accelerating.

Is this just the normal operation of 4A that everyone is experiencing, or should I have this checked out?

If the answer is it is normal and everyone experiences it... why? What causes it? I have had a number of vehicles with 4A capability and I have never had such a harsh difference between 2WD and 4A.

 

If you are driving it in 4wd on dry pavement it will likely have some vibration and noise, possible a dull whine. This is pretty normal on a trucks 4WD system.

You said you had other vehicles with 4WD, if you are referring to vehicles like a Ford Edge/Explorer, basically most things that aren't trucks and some SUVs (Nissan XTerra for example), they aren't nearly the same type of 4WD system. The 4WD systems in vehicles like an Explorer basically main drive one set of tires (often the front) with 70% of torque and the rears maybe get 30%. Some can modulate the amount, but it's almost never 50/50, and in many cases it's almost 100% to the front or back. They are much "softer" systems and barely qualify as 4WD.

 

Mine also sounds different when in 4A.

 

4A can be driven on anything. Dry pavement is not an issue. look up what 4A is...




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This! And yes my 4A sounds and feels like a 25 cent massage chair at the mall. Trust me, there will be people that chime in and say it's smooth as glass....and then there's the rest of us. Thank your lucky stars you don't get to deal with it in 2WD like some of us...

 

I use 4A on any conditions, but mainly wet... and that is perfectly safe and will not bind on turns... and that has nothing to do with the sound... as others have said.

Sounds like it is common... I just wanted to make sure I was not missing some fluid in my transfer case or something...

 

I have the same issue, you can feel the vibration in the steering wheel when accelerating or when applying power while in a soft turn at speed. I have been to the dealership several times over 6 months and was told by the service manager and shop Forman ford is still searching for fix but know there is an issue. I can't believe it's taking this long. I have had several trucks with 4A and have never had this issue.

 

If I remember correctly when you shift to 4A, it locks the front hubs. This way when extra traction is needed only the transfer case has to do anything. Otherwise you would be waiting for the hubs to engage/disengage every time the rear tires slip a little. In 2wd the front hubs are unlocked. The vibration could be from the front diff or the front driveshaft. As these components wouldn't be rotating in 2wd. I could be wrong on how the system operates though.

 

4A shouldn't make any noise unless the system is engaging. It shouldn't engage unless it detects slippage. (As I understand it.) This has been my experience with it anyway. I can feel it when the thing engages. This is confirmed by the instrument cluster as you can display the power allocation to the wheels.

 

I feel a little bit of vibration and noise in 4A as well. Probably because of the extra load on the transmission and transfer case. Not really worried about it.