Winter weather driving

[Sparkherd]

Hmmm. So is 4H engaged in a fundamentally different way than 4A, or is it just engaged for very short intervals, or both? Of course I mean mechanically/hydraulically etc. I know the switch/mode is different.

4H is locked; no differential action between front and back.
4A employs a computer-controlled clutch wherein the computer senses slip on the rear tires and employs some sort of stepper(?) motor to engage the transfer case clutch to apply power to the front axle.
In my Not-So-Humble-Engineering Opinion, it's a very slick system.
Somewhere on here, there's a video with a teardown of a 4A transfer case that was flat-towed incorrectly and required a rebuild. The video is a great delve into the mechanical aspects of the system. The computer part, I (and others) are still trying to figure out...

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[5GENIDN]

No I am not.
As long as you travel in a straight line, nothing binds up.
Unless you have different sized tires on your vehicle?!?

This part you obviously know but bear with me here....

When turning a corner your outside tire has to travel farther than your inside tire. So when you lock your differential you force both wheels to turn at the same speed. If there is no slippage on the inside tire it will hop and give a lot of indication that it should not be locked... Okay we get that.....

4H or 4L "locks" your transfer case. 50% power to front 50% power to back.... Now the differentials are not locked so they can differentiate when you go around a corner and well the gearing is the same in the front and in the back right? Well technically no.... There is a slight variance in tire size, a slight variance even in matched gears. It is very small. This means that the front tires will be traveling ever so slightly different from the rear tires. It is very subtle. because it is so subtle it does not give off the same dramatic effect that a locked differential will give you. But slowly over a large distance this difference starts to add up. this slowly creates more and more bind in the system. This is what starts wearing the bearings more than anything. especially the bearings in the U joints/CVs.... it putts more and more pressure on the gears and their bearings. It puts torsional stress on the axles. It simply accelerates wear. Most people do not even notice it because it is so subtle.... But it is a problem... A bearing that might have made 200,000 miles now only lasts 80,000 miles. It is hard on the whole system. That is why the engineers that design these tell you explicitly not to do it. You need a little slippage at the tires for this not to happen.

4A allows differentiation within the transfer case. That is why it is perfectly fine to use 4A on dry pavement.

 

[Ducati1098]

Hmmm. So is 4H engaged in a fundamentally different way than 4A, or is it just engaged for very short intervals, or both? Of course I mean mechanically/hydraulically etc. I know the switch/mode is different.

It’s the exact same, 4A just modulates torque applied to the front where 4H locks the clutch.


Four Wheel Drive Auto

In this mode the transfer case system is active all the time and requires no input from the driver. The AWD control system continuously monitors vehicle conditions and automatically applies torque to the front driveshaft. This is done through the use of a multi plate clutch pack inside the transfer case that modulates torque delivery to a chain drive that is connected to the front driveshaft. If any wheel slip is detected on the vehicle or if the vehicle is in a handling event the AWD control system commands the transfer case actuator to apply torque to a ball ramp cam system which then applies an axial force into the clutch pack.

Four Wheel Drive High Range

In this mode the clutch is essentially locked. This would lock the front and rear driveshafts together giving the vehicle maximum traction. It is a similar mode to the ESOF system 4WD high (4H) mode

 

[swamp2]

RTFM to me @Ducati1098 ? Thanks, great explanation!

 

[FilmcoBronci]

The above description by @Ducati1098 is magic. I'm going to ask Ducati to explain GOAT Slippery vs 4A

We have about 62k flawless miles driving snowy and icy roads daily in Colorado during the winter. We change Tranny and transfer case fluids every 7K
Here are some "How we Roll" insights and habits. We have had zero Transfer or transmission issues. Caveat, we do quite a bit of off-road trail driving on crusty mountain roads for work, but never heavy rock crawling. Most of our 4-Wheeling is on dirt and mountain roads with nominally steep grades but we do venture onto quite a few snowy mountain and ranch roads so we use the full range of GOAT and 2H/4H combinations daily.

4H GOAT Slippery is our go to on generally icy and snowy pavement above 40-60MPH
2H When we are on Dry Pavement
2H GOAT Slippery on variable pavement with icy patches has been an excellent go to.
We always keep a finger near ready to tap the 4H button.

Dont be afraid to play the GOAT modes like a piano. The road is a symphony.
Sometimes it's quiet interlude and sometimes it will try to kill you with cowbells and cymbals.
The buttons and dial are there for a reason and work pretty well when used appropriately.
Us Old folk off-roaders from the days of early Bronco's and CJ's are familiar with the routine.

As multiple previous posters have indicated, without 4A, never run 4H on Dry Pavement.
Non-4A equipped Bronco 6Gs function like classic old school 4WD vehicles.
Only difference is you don't have to get out and lock the hubs
4H is meant to be used solely in low traction environments.

Previous posters are also correct that use of 4H in high-traction environments will lead to excessive binding of transfer case and axles, guaranteed to deliver your 6G to the medic.

No Slippy/No Sloppy/No 4H

 

[FilmcoBronci]

It’s the exact same, 4A just modulates torque applied to the front where 4H locks the clutch.


Four Wheel Drive Auto

In this mode the transfer case system is active all the time and requires no input from the driver. The AWD control system continuously monitors vehicle conditions and automatically applies torque to the front driveshaft. This is done through the use of a multi plate clutch pack inside the transfer case that modulates torque delivery to a chain drive that is connected to the front driveshaft. If any wheel slip is detected on the vehicle or if the vehicle is in a handling event the AWD control system commands the transfer case actuator to apply torque to a ball ramp cam system which then applies an axial force into the clutch pack.

Four Wheel Drive High Range

In this mode the clutch is essentially locked. This would lock the front and rear driveshafts together giving the vehicle maximum traction. It is a similar mode to the ESOF system 4WD high (4H) mode

This is excellent. Thank you.
Curious, how does GOAT Slippery Differ from GOAT 4A?
Thanks!

 

[Ducati1098]

RTFM to me @Ducati1098 ? Thanks, great explanation!

lol no. This is out of the workshop manual which I know not everyone has access too.

Plus they do a better job of wording/explaining everything than I would, so I just copy and pasted.

 

[Ducati1098]

This is excellent. Thank you.
Curious, how does GOAT Slippery Differ from GOAT 4A?
Thanks!

Slippery mode lowers throttle response and changes transmission shift points.
For those with advanced transfer case it defaults to 4A, for those with the part-time transfer case it will default to 2H or 4H I can't remember which one.

 

[BroncocnorB]

lol no. This is out of the workshop manual which I know not everyone has access too.

Plus they do a better job of wording/explaining everything than I would, so I just copy and pasted.

Oh so you’re like qualified to be president of Harvard?

 

[Jsullivan]

It's funny hearing lower 48 people's opinions of when to use 4x4.

Our roads aren't salted, so what looks like pavement is actually ice. 6 months of the year I'm in 4H or 4A and run studded a snow tires. You can run 100 mph in 4H it won't hurt a thing, just don't turn sharp on dry pavement. Ran all my 4x4s like this for decades, never had to repair a differential or T-case. I've seen way to many trucks and suvs go flying off the road because they had it in 2wd and lost it on a hill or curve. You have 4x4, use it.

www.youtube.com › watchHARDY - 4X4 (Lyric Video) - YouTube

 

[Ducati1098]

Oh so you’re like qualified to be president of Harvard?

Exactly haha

 

[FilmcoBronci]

lol no. This is out of the workshop manual which I know not everyone has access too.

Plus they do a better job of wording/explaining everything than I would, so I just copy and pasted.

None the less, you pasted well. Lol

 

[CarmeloS]

Would I be fine doing donuts in taco bell with my 2dr?

 

[helifino16]

No driving Mode will 'prevent' you from getting stuck or losing control. Using 4H to keep from slipping is like carrying an umbrella to keep it from raining. Only careful driving will keep you safe. Knowing you have the capable vehicle to get you out of just about any situation will be all the reliability you need. It's not a matter of IF, it's a matter of WHEN and whether you're prepared to remedy the situation. The best mode to be in is 4A (if you have it) or 2H. When you get into trouble, you should be able to get out of it in 4L. If you're driving like a jack-ass in foul weather, you probably deserve to get messed up (FAFO).

 

[RobWTX]

So the moral of the story is, don't drive on snow or ice, got it!

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