2003 Exp no 4 x 4 Hi, Lo ok

[stevebigos]

Hi folks, new guy here. I just bought a 2003 EB Exp. The 4 x 4 Lo works fine, clunks going in and out of 4 x 4 as it should, and all 4 wheels are powered. But I have no 4 x 4 Hi. The 4H dash light comes on when I start the vehicle, then goes out as it should. I have tried various combinations of moving the dash switch to 4 H when moving, stopped, engine on/off, park, neutral, etc, no go. I do hear a faint click inside the rear drivers door pillar (in the seat belt winder area) when switching to 4H, so something is happening, leading me to think the dash switch is most likely functioning. The 4H light never comes on and no transfer case clunk. Fuses are all good.

I looked for vacuum hose leaks and found nothing obvious. Also looked over the transfer case motor and don't see anything obvious.

Looking for advice, also looking for theory of operation of the transfer motor, and advice on the AWD position as I see no indication that it is or is not working either. Also would like to know the steps for changing both diff and transfer case fluid. I did buy the Ford friction modifier for the diffs.

Any help is appreciated. Thanks.

 

[FordandPolaris]

The clunking sound is the transfer case engaging low range gearing. You shouldn't hear a clunking when selecting 4x4 high. Basically the A4WD uses the speed sensors on the wheels to decide how much torque to send up front. In dry conditions it should drive only the rear wheels for the most part. I do think it sends some power to the front (>10%) all the time. If the sensors detect the rear tires slipping, it will focus more power up to the front.

The way I test mine is in the winter, I first start in 2H, hit the gas, rear wheels spin in the snow, I go almost nowhere. Come to a stop, select A4WD, hit the gas, and I go with no problems. Now since you are in Florida, you might have to come up with a different way to lose traction, but that is the best way to see if the system is working.

Only way I know of to test the 4x4 high (only if you are completely confident it is not working) is to switch it to the 4x4h setting, and turn on dry pavement. You will feel the front end bind up and not like the turning. Back up about the same distance to unbind the front end, and disengage the 4x4. If someone has a better method though, I would like to hear it as I know it is not good for the front end to perform this test.

 

[stevebigos]

The clunking sound is the transfer case engaging low range gearing. You shouldn't hear a clunking when selecting 4x4 high. Basically the A4WD uses the speed sensors on the wheels to decide how much torque to send up front. In dry conditions it should drive only the rear wheels for the most part. I do think it sends some power to the front (>10%) all the time. If the sensors detect the rear tires slipping, it will focus more power up to the front.

The way I test mine is in the winter, I first start in 2H, hit the gas, rear wheels spin in the snow, I go almost nowhere. Come to a stop, select A4WD, hit the gas, and I go with no problems. Now since you are in Florida, you might have to come up with a different way to lose traction, but that is the best way to see if the system is working.

Only way I know of to test the 4x4 high (only if you are completely confident it is not working) is to switch it to the 4x4h setting, and turn on dry pavement. You will feel the front end bind up and not like the turning. Back up about the same distance to unbind the front end, and disengage the 4x4. If someone has a better method though, I would like to hear it as I know it is not good for the front end to perform this test.

Thanks for the idea on checking with the steering. I did notice the steering bind on several others I test drove, so good idea. When I tested the 4wd L I used a dirt road, stomped on the gas and the 4 wheels grabbing was noticeably different than when in 2wd.

Still, I should see the dash light come on and I think hear a transfer case clunk just like when going into 4L if the system is working in 4H.

 

[stevebigos]

Test 4H in dirt and it is actually working. Now I need to troubleshoot the light circuit. Any ideas?

 

[FordandPolaris]

I would say replace the light bulb. Probably was just faulty from the factory.

EDIT: Just kidding, I forgot you said it comes on when you cycle the key just before starting the truck. I am not much of an electrical guy, hopefully others will have some ideas.