I wanted to get to the bottom of some common 4WD questions that have been circulating in my head since it started snowing in the beginning of December. I have been using my 4WD alot on my 1995 F350, but I always was curious about certain ways of getting it into 4WD.

1. If you put it into 4WD without locking the hubs, it doesnt do anything obviously, but if you then lock the hubs with it already in 4WD, will it work still?

2. Can you put 4WD in while moving?

3. Do you have to lock the hubs if your going to put it into 4 low?

4. If you have it in 4 wheel drive while coasting, is it the same thing as if you were in 2WD? Or because the front differencial is now connected to the driveshaft, does it give some sort of extra traction even tho theres no power going to it. For example, while coasting down a hill while its snowing, is there any sort of extra traction because the front axle is locked or is it the same as being in 2WD and coasting?

5. Lastly, howcome 4 low is way more powerful than 4 high, is it splitting more power to the front differencial or is it using a differnt gear or what?


If you can answer these questions it be a deep help to helping me understand the uniqueness of 4WD, I hope this doesnt come off dumb to you guys, but these are deffinately questions I would love to learn.

 

1. Yes

2. As long as the hubs are already locked in and your front wheels are traveling the same speed as the back ones (not spinning in the back). The hubs will keep the front driveshaft going at the same speed as the rear driveshaft so it will slip right into 4wd (i think up to 45 or something you can shift in or out)

3. Nope. A lot of people use 4 low and 2wd to back large trailers up because it puts less strain on the transmission and makes it easier on the driver if its a manual.

4. A small amount, say you were downshifting.. in the snow in 2wd the back tires would probably start to slip, but there might be enough traction at all 4wheels when in 4wd that it'll slow you down instead of slipping. Kind of something you have to get a feel for when driving.

5. 4 low is basically double the tq going to the wheels. The 4 low in a transfer case is 2:1 or greater usually.

Hope I helped.

edit: This link may be useful as well http://auto.howstuffworks.com/four-wheel-drive.htm

 

[QUOTE=FordF350Baby]I wanted to get to the bottom of some common 4WD questions that have been circulating in my head since it started snowing in the beginning of December. I have been using my 4WD alot on my 1995 F350, but I always was curious about certain ways of getting it into 4WD.

1. If you put it into 4WD without locking the hubs, it doesnt do anything obviously, but if you then lock the hubs with it already in 4WD, will it work still? To tell the truth, I didn't actually try this, but I know you aren't supposed to do it. You are suposed to lock the hubs then engage 4wd

2. Can you put 4WD in while moving? Some models yes, yours.... more than likely not

3. Do you have to lock the hubs if your going to put it into 4 low? no, but you won't have 4wd. It would be like haveing a 2 lo, just might not be a good thing to do

4. If you have it in 4 wheel drive while coasting, is it the same thing as if you were in 2WD? Or because the front differencial is now connected to the driveshaft, does it give some sort of extra traction even tho theres no power going to it. For example, while coasting down a hill while its snowing, is there any sort of extra traction because the front axle is locked or is it the same as being in 2WD and coasting? If you would put it in 4 low and 1st gear down the hill, it would have a good crawl ratio and in a way you would have good traction while coasting.....?

5. Lastly, howcome 4 low is way more powerful than 4 high, is it splitting more power to the front differencial or is it using a differnt gear or what? 4 low has a lower gear. Some transfer cases are different, but it could be around 2.5:1, and 4 high is only 1:1
So 4 Low takes your gear ratio and multiplys it by 2.5
Only down side is all the extra force/pressure on the u joints
[QUOTE]

I'm sure others will chim in and help out a little more.

 

You guys answered awesome! Very helpful!

 

His truck is shift on the fly into 4-high with the hubs locked.
Me, as long as there's snow on the ground, the hubs are locked, then it's just a matter of pulling the lever if I need it.

 

Yeah well see I always thot I had to come to a complete stop to get it into 4 wheel drive, so I figured what would be the point of driving around with the hubs locked and putitng wear and tear on the front end, but i deff would save myself having to stop if i knew u could put it in while driving. Thanks guys

 

> 4. If you have it in 4 wheel drive while coasting, is it the same thing as if you were in 2WD?

No, because while going down the hill, especially around a curve, it is a lot easier to pull the rear wheels back into track if they slide with the front end pulling. Plus, the front end is less likely to slide straight through a curve because they are being pushed by the rear. Even coasting with the foot off the gas, the wheels are still being powered.

 

Exactly my question, thankyou, I had a feeling it had to be helping in some way

 

Can you put it in 4wd and then lock the hubs? Sure...why would you want to? Since they are manual hubs, the only way you are going to engage them is with the truck sitting still. With nothing moving in the driveline, it doesn't matter if you already moved the lever to shift the transfer case.

Can you engage 4hi while moving? Yes...shift on the fly up to 50 mph (if I remember the manual correctly). Just don't do it with the wheels turning at different speeds. For example, I just turned off a well cleared road onto one that's icy enough I start to spin the rears. If I immediately shift the transfer case into 4hi, with the fronts just rolling along and the rears spinning free, I'm going to shock load the driveline and/or grind some teeth off the gears in the transfer case. Alternatively, I could just lose control of the truck because of the sudden change in speed of my steering wheels and stuff it into a tree. The right way to handle this one is to get out of the gas enough for the rears to stop spinning free and resume rolling at the same speed the truck is going, then shift the transfer case and drive off. You don't have to come to a stop, just don't be spinning the wheels under power.

NOTE: this only applies to 4hi. If you need 4low, the truck must be stopped and the transmission in neutral before you can shift. 4low is useful not just for the extra torque provided by the lower gearing, but also for better control at low speeds, especially engine braking on steep hills.

The easiest way to handle things is to just lock the hubs before you leave if you think you may need 4hi. You can then shift in and out of 4hi as necessary without having to stop or get out.

Hope this helps.

 

Thank you, it makes good sense to me now. Being able to put it into 4 hi while moving with the hubs already locked is very cool news. I never thought you could do that, I figured it would grind the gears.

 

On a lot of the older trucks, it does. Most newer ones have the ability to shift while moving. That being said, I had to have a newer t-case rebuild one time, and the guy said it was worn out from shifting on the fly. His recommendation: stop if you can. Only shift while moving if absolutely necessary.

 

great point, and thats probably why I dont risk it in the first place, is the chance that I could ruin the front differencial ect. I figured whats the harm to stop, it would make me feel way more comfortable knowing I am not causing any internal damage. Thanks

 

I have a 99 eddie B expy. Its awd,4wd,4lo. Question can it be made 2wd,4wd,4lo?