hello all. i am new to the forum, but i am on my 6th ford truck. i am in california and have NEVER had the need to use 4wd. i pull a boat often, and have pulled a few racecars, but all in good weather conditions. i have a new to me 16 lariat screw. my very first vehicle with 4wd options. can anyone provide a good situational explanation when this should be used, should i use them every so often to keep everything working well? seems like a really dumb question, but i could really use a beginners course. explain like i am 5. thanks in advance

 

There’s 4hi and 4low. You can safely try both of them on dry pavement to keep the parts moving but only go in a straight line, especially in 4low. It’s better to do both on gravel if possible.

4hi can be engaged just by turning the ****. It’ll even go in 4hi while moving. That’s called shift on the fly, and it works up to a certain speed. Shift it at low speed tho, or not moving at all. And you can essentially go as fast as you want with it on, but remember the rule above about dry pavement not being a great place for it.

To shift into 4low, stop, shift transmission to neutral, put the selector in 4low. Wait til the truck confirms you’re in 4low. Make sure your foot is firmly on the brake, and shift to drive. You’ll feel the truck lurch up. You can let off the brake and drive slowly. 4low uses a different gear ratio and is really for crawling or getting unstuck. Again, if you have to do it on pavement, go very straight and slow and for not very far. 20ft is prob enough. On gravel you can safely go farther. To change back to 2wd or 4high, shift to neutral, then out of 4low, then back to drive.

We can talk later about the locking rear axle if you have that. But same rules apply above about pavement and not turning.

 

appreciate that reply. so i could use 4hi in a heavy rain with no real issues, but 4lo would be kind of a desperate situation. hopefully i won't need that, but i was truly lost at when these would be of importance. thank you

 

No. Do not use 4 Hi or Low on pavement for any distance. There's no advantage in doing that, and it may damage your drivetrain. Only 4A (auto) mode, if you have it, is designed for use on pavement. See your manual and Ford's owner web site for details. This is a decent overview: https://owner.ford.com/support/how-t...-systems.html#

 

As someone that tows a boat, 4WD can be useful to you on slick boat ramps. Just keep the steering wheel straight while the front hubs are engaged.

 

The advantage to doing it is that you at least get the components moving. If you're driving in a straight line for a short distance, you won't cause any issues. The issues happen on pavement when your wheels are not traveling the same distance (because you're turning) and your transfer case has the front and rear driveshafts locked, spinning at the same rate, but the wheels are not turning at the same rate and they can't slip. "no, not for any distance. there's no advantage in doing that". I love when people speak in absolutes. Anyway, good emphasis on being careful with it, pavement is not the preferred place to test the 4 wheel drive system, gravel or grass or sand or worse is very much preferred. But if it's been months since the system has been used, you don't have easy access to something that's not pavement, it's OK to shift in and out of the 4 wheel drive modes and let the truck roll for a little bit in a straight line, and then shift back to 2wd.

If he has 4a, he can leave it in 4a all the time and if a wheel starts to slip, the system will automatically engage 4hi. This is good for the rain. I wouldn't use 4hi in the rain on pavement unless the conditions are really really bad, and even then you still probably don't need it.

 

Can someone explain why turning the wheels while 4hi/4lo is engaged is harmful? Doesn't that defeat the purpose of 4WD if one is not allowed to steer while it's engaged?

 

With the center differential and hubs locked you will create bind in the drivetrain when turning without any slip (like on a gravel road or in snow) as the wheels do not all travel at the same speed. Normally this is harder on your tires than anything else. if you pop it into 4 Hi or 4 Low in a parking lot and make a tight turn, you can actually feel the bind - only try this in your truck and not mine!

Cheers

 

4X4 hi / low should only be used on loose surfaces mud snow gravel rock broken uneven surface.
the wheels will work against one another a tear the system apart.
Only 4A can be used on smooth pavement.

 

The idea is that you're using 4wd in situations where your wheels are on a slippery surface, so you don't get the drivetrain bind that you'll get if you're using 4wd and turning on a surface like pavement that doesn't allow for any wheel slip. The tires slip long before you build enough strain in the drivetrain to cause an issue. Does that make sense?