This is my first car / truck with a 4hi only mode and there seems to be a lot of varying information when and when not to use it. Doing a search I've seen "no high speeds and no dry pavement". The manual, however mentions nothing about speed just "use for slippery conditions."

I've also read it's technically ok to use under any circumstances just don't turn and make the front end "bind" with dry conditions but straight is fine.

Are these precautions just to make sure someone doesn't stick it in 4hi and use it year round? All of my previous vehicles have been either 4A or AWD. Even my 98 Jeep had "4WD Full time and 4WD Part time" modes.



So here's my question:

Today we had a lot of snow / mix slush on the ground with freezing rain. I have a lot of back roads near our house and had to drive to CVS to get cold medicine for my daughter. It was really bad weather (frozen rain, snow, etc). Some roads mainly by my house were fully covered over with snow and ice.

However, some of the roads leading to the store were off / on. Meaning some parts were fully covered over, others had dry patches where previous cars drove and dried out groves on the road.

I left 4hi on the entire time - never noticed any wheel hoping when turning at stop signs, but it made me wonder - since I don't have the 4a option, am I supposed to be turning the switch on and off as I drive through dryer areas and wetter areas? Or is it ok to leave on for my entire trip since it's on and off bad traction?

 

My logic, leave it in 2 wheeldrive, until you "really" need 4X. The only thing 4X4 gives you is the option of taking off with out spinning, or when you get in trouble. I live in northern Michigan, and I just about exclusively drive a RWD Ranger, all winter. I will take the 150 at times, when I really need to, ie., when I've got around 6" of the heavy stuff, or more.
People seem to be over thinking the whole 4X4 thing this year for some reason.
Even when I chose to drive my pavement queen 150, it rarely sees 4X4 on patchy covered, or for that matter, icy packed down snow.
But, if it makes anyone feel safer, go ahead and leave it in 4X4, on at least wet pavement conditions, it'll let you know if it doesn't like like going around a corner.
When I first drove this 150 a few years ago during it's first winter, it really surprised me how stable these trucks are on snowy icy conditions. Ford made quite an improvement over my older Superdude 4X4.

 

I tend to flip it on and off while driving and just kinda let off the gas when doing the switch.

ill run it on the highway at 50-60 mph if I need to lane change and there's that slush pile that builds up between lanes. It also helps getting up back roads that are snowy, so it does do more than just let me get off a red light.

It is annoying to switch constantly so i too tend to try and leave it off until absolutely necessary.

 

Just curious if the front diff is an open style why would it make any difference on dry pavement if there is no slippage? Are the two halves somewhat tied together?

 

Never mind , thought about it some more. In a turn the abs sensors are going to count tire revolutions and apply one wheel spin control sort of locking the two halves on the front diff. Which on dry pavement would creat binding. Is this right?

 

No that's not it.

The front and back diffs are rigidly attached when it 4wd. When making a turn the front and back take a different radius meaning the front and rear wheels are turning at a different rate. This is why you get mind when turning in high traction conditions.

If there is snow on the ground I am in 4wd for safer driving.

 

Sorta kinda. The axles are locked to each other through the transfer case. 4H is/used to be, called 4 High locked. It acts like the differential in a spooled type axle. The only slippage will be from the tires basically skidding on hard/dry surfaces.
There is a type of transfer case called "full time" In the full time mode, power will be transferred to the axle with the least amount of friction, just like an open differential. Could be the front, could be the rear, depends on traction, or lack of.
And there is another type full time, that will transfer power to whichever axle has the highest amount of traction, like a limited slip axle in your transfer case. I think it was Jeep at one time, maybe still do, that had the latter. Maybe some other makers used that as well, and likely still do.

 

Seems we can post this stuff over and over, and over...

You hit the nail on the head in your post, OP.

it's technically ok to use under any circumstances just don't turn and make the front end "bind" with dry conditions but straight is fine.

The manual, however mentions nothing about speed just "use for slippery conditions."

Your trip to CVS used it 100% properly.

If you want to see wheel hop, go into a dry parking lot. Engage 4x4, and crank the wheel over and start to make a turn. You'll feel it. Straighten out, turn it off, then do it in 4x2 and you'll see.

 

While I appreciate your efforts I am well versed in automotive drivetrains.
In the case of my post I was speaking about our trucks specifically. It is a direct drive system with no allowance for slippage within the transfer case.

 

Wasn't really directed at you, just quoted your reply, and tried to help the OP understand.

The axles aren't what are binding, the Tcase internals are.
OP, sometimes the bind might prevent the system from "unlocking", happened a lot in the old days. The trick was, straighten your steer tires, and move in the opposite direction from what you were going a few feet. It'll relieve the pressure on the internals and allow it to shift out. I've never heard of this being a problem with these motor driven systems, but it could be with the older style manual ones. Just in case.