Question about 4WD Operation and Testing

[TechGuru]

1. How can I verify my 4WD works? I tried jacking up one front tire and with key on engine off I hit 4x4 hi and the light came on but the front wheel still spun freely.

2. If the above is normal, is there any way to keep the front locked when you turn the engine off? Reason being is if one is off roading and parks front down on a steep hill with only the rear being locked by the transmission parking brake it's possible the tires may slip and slide down the hill. It would nice to be able to lock all 4 wheels in park.

 

[dla]

A couple ways:

1. Jack all 4 wheels off the ground - this way you can see how 4 auto works, which is a little mysterious.
2. Drive on wet pavement, select 4 high or 4 low and turn a circle - you'll feel the drive train bunch up and the tires will slide. When you select 4 auto that bumping/luching will go away.

I don't know what the power split is between front and rear in 4 auto, but I know that if you jack the rear wheels off the ground and get in and start it up, put it in gear, you'll feel power to the fronts.

I also don't know how to completely turn off the partial 4wd.

Also, if you do jack the rear off the ground you can check the limited slip in the rear - both wheels should turn the same direction when you turn one by hand. If you just jack one rear wheel off the ground, you can use a torque wrench and see the break-free torque required - should be around 25 ft/lbs or so.

 

[Joe in NY]

I do NOT recommend you driving in 4 low on dry pavement. That is how you break your drive train. Nothing gives until something breaks.

Also, No it is not possible to engage 4WD with key off. It uses an electric clutch only when ignition is on. I don't like it either.

4WD auto varies from 0% to 100% engagement of transfer case. The front diff is OPEN while the rear is OPEN or LIMITED.

 

[dla]

Here is a description of the system
Wiki Article on Ford's 4wd system

 

[SideTrackTap]

When test driving an 86' Bronco years ago, to test the 4x4, my brother engaged the four wheel drive (auto hubs, manual transfer case) and turned the wheels all the way to the right then left (or vice-versa) on dry pavement. If the four wheel drive was working, you would feel the front wheels binding up and the steering wheel jerk, meaning power was being applied to the front wheels.

When I test drove my 02' Explorer, I did the same thing.

While I agree with Joe in NY and it even says this in the owner's manual; I wouldn't do this on a regular basis, but I think to momentarily test the four wheel drive, it's ok. And I think something that is key here is that you don't give it gas when you try this. When you do this, you are simply coasting at a slow speed and turning the wheel just until it starts to bind up.

I'm not sure how the 03' is, but the 02' (mine at least), you have to put it into 4x4 low. Auto only works if the computer senses wheel slip.

Chris