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4WD button on dash doesn't light up

First, check all fuses. Consult your owner's manual look for additional fuse box locations that might not be with your main fuses. Check the light bulb itself to make sure it's just not burnt out. Conduct some simple ohm meter/continuity tests to see if any wires are obviously bad. Look under the hood and follow your wiring harness as it relates to the dash button, and make sure nothing is loose or broken or damaged. If all this proves nothing, then see if the 4wd is working in 4wd Lo (see below on How do I test my 4wd?). If the 4wd is working and it's just the light that doesn't work, I'd not worry about it unless it just annoys you. On the other hand, if you really depend on your 4wd, then ask yourself if it's worth wondering if it's going to come on when you really need it? If in doubt, get it fixed.

If your question pertains to a Ford Explorer (which is common), try

4WD does not seem to engage: how do you know?

To test your four wheel drive, see below on how do I test my 4wd. But let's say you tested it and it's not working. In this case, make sure the electronics diagnostics above have been followed. Then check drive lines and suspension parts to make sure everything is connected and seeminly working. Now you're down to checking the hubs themselves. This can be a job. If you need to dig into the hubs to see if the locking mechanism is working, you'd best know what you're doing or take it to a shop.

What does Full Time 4WD and All Wheel Drive
(vs. 4WD) mean?

Full time 4WD, All Wheel Drive, and 4WD are different things. Real 4WD means having hubs up front with a transfer case (usually). Full Time 4WD usually means real four wheel drive but automatic hubs (like TJ Wranglers). You still have the transfer case and hubs, it's just that the hubs are automatic. All Wheel Drive is not 4WD.  AWD means the computer helps the differential figure out where power is needed and diverts the power to the spinning wheel. It's usually done electronically (with a viscous coupling). It's not as dependable as 4WD; but may serve well for general purpose 4wd use.

BUT NOTE THIS: they're all misnomers! 4WD means you have TWO WHEELS DRIVING. That's right. One wheel in the rear and one wheel in the front is driving the vehicle. Get this; in a normal passenger car, ONLY ONE WHEEL is driving the car. Why? Because the differential (pumpkin, rear end) is putting power to the ground on one driving wheel, differentiating between the two tires to determine where best to put the power. But only one gets the majority of the power. That's what differentials do.

So with four wheel drive, you additionally engage one tire up front (if you're rig is rear drive). Now you have one tire in the back and one up front, driving the rig. Quite confusing, huh? Well, that's why you hear four wheel drive enthusiasts talk about *lockers* and limited slip. Lockers lock up the wheel not getting the power from the differential. See Lockers for more.

More on All Wheel Drive vs. Four Wheel Drive

Should I get manual (locking) hubs instead of
full time 4WD?

No. Unless you're a serious four wheeler who wants the ability to lock hubs in and out, don't worry about full time hubs vs. locking hubs. Yes, by going to hubs, you might save on gas mileage and vehicle parts wear and tear, but it's usually a very spendy operation. I have automatic hubs on my Wrangler and it's just fine.

The advantage is in towing for sure.  If you flat tow your rig, then locking hubs are nice because you can lock the hubs OUT and reduce drag and wear and tear when towing.

How do I test my 4WD to see if it's working?

First off, don't worry about your 4WD in the setting 4WD Hi. This usually means it's on intermittantly (when needed). The time to test it is in 4WD Lo. This is the real test of four wheel drive parts. In 4WD Lo, it will turn (steer) a lot harder. Follow your Owner's Manual when playing with 4WD Lo. Don't go fast and do it on dirt if you can. You can also jack up the vehicle, engage the 4WD Lo, and see if both front tires turn at the same time (in other words, you can't stop one tire from turning if the other is turning). This will tell you if it's engaging or not.

Where is a good place on the Internet to talk 4WD stuff?

General Tech Talk Rig Fixits Gears
Rig Diagnostics Noises Tires
Shocks Rig Modifications On-board Air Systems
Winches Wheels Buying a 4WD
GPS & Radios Electronics Great 4WD & Product Links
Transfer Cases 4WD vs. AWD Rig Builders
Starting Problems Steering & Braking Find a Good Mechanic
General LINKS BACK to Products BACK to Del's Home Page

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