4wd auto vs 4wd Low vs 4wd High

[Mikebighorn]

What’s up Ram fammm.
I am curious about the difference between 4wd auto, low and high . And when to use it and not to use it

 

[devildodge]

We have this question come up often, lots of threads about it, but the jist is 4 low is only when maximum pulling power is needed and off road control is expected. Basically slow speed off road use.

4 Hi is your locked 4 wd. Used in constant slippery conditions, never on dry pavement, off road at higher speeds or at highway speeds during snow, etc.

4 Auto can be ran in any condition, but is never really locked in 4wd. Use this anytime, even on dry pavement. It will detect slippage and send power to the front, but without slippage is just like 2wd. Useful in a rain storm or a dreary day.

On constant slippery surfaces 4 auto can actually become a hindrance though, but it will help get the power down like when merging onto a highway.

Read up. Lots of opinions and experiences here. I can post links if you can not locate them

 

[ZombieSlayer]

The 4WD selector threads should be merged and stickied

 

[Juli_hoop]

So what should be used in deep loose sand? 4lo with locked rear diff? or 4hi with locked rear diff? it is my understanding that the locking rear differential disengages at 20mph which doesn't really help when trying to keep speed on loose deep sand? so would it be better to just use 4hi with no locked rear diff?

 

[HotHareSpey]

So what should be used in deep loose sand? 4lo with locked rear diff? or 4hi with locked rear diff? it is my understanding that the locking rear differential disengages at 20mph which doesn't really help when trying to keep speed on loose deep sand? so would it be better to just use 4hi with no locked rear diff?

You should use low nearly any time you use the locking diff - the diff turns off at 20mph in H4WD but in L4WD it goes up to 40mph and you get a lot more torque

 

[Juli_hoop]

You should use low nearly any time you use the locking diff - the diff turns off at 20mph in H4WD but in L4WD it goes up to 40mph and you get a lot more torque

That I did not know thank you. I will be using 4low and diff locked this weekend then haha.

 

[Wolf]

That I did not know thank you. I will be using 4low and diff locked this weekend then haha.

You want 4hi on loose sand. I learned that from the locals in Hawaii after getting my rental Jeep stuck on a beach in 4 lo. Also lowering tire pressure to 15-20lbs was suggested by them.

 

[Juli_hoop]

You want 4hi on loose sand. I learned that from the locals in Hawaii after getting my rental Jeep stuck on a beach in 4 lo. Also lowering tire pressure to 15-20lbs was suggested by them.

I know lowering the air pressure is best so the tire floats on top of the sand but 4hi? I won’t even be able to lock the rear diff in 4hi if it’ll disengage going 20mph. You’d think I’d be the other way around (disengage at 40mph in 4hi instead of 4lo)

 

[devildodge]

The 4WD selector threads should be merged and stickied

Doesn't matter. We have tried to combine things and sticky them...too many posts to look through, just ask the same question that has been answered numerous times hoping that you will get the answer you want not the one that was figured out.

I really love the questions that are solely opinion, no right or wrong answer, but the question is posed a different way, just slightly, and we get one or 2 new opinions that make more sense...what are we to do with that.

 

[GerryS]

I know lowering the air pressure is best so the tire floats on top of the sand but 4hi? I won’t even be able to lock the rear diff in 4hi if it’ll disengage going 20mph. You’d think I’d be the other way around (disengage at 40mph in 4hi instead of 4lo)

It depends on how fast you want to go. In 4lo your top speed may be 35-40 mph. Think first gear on a ten speed bike. Good for crawling out of some deep s**t.

Otherwise, 4hi for normal speeds.

Gerry

 

[Mikebighorn]

Wow thank you for the great responses . So from what I gathered . In rain or snow conditions either 4wd high or auto will work . But high might be better for snow conditions because of the constant slippery conditions

 

[devildodge]

Wow thank you for the great responses . So from what I gathered . In rain or snow conditions either 4wd high or auto will work . But high might be better for snow conditions because of the constant slippery conditions

Yes. 4wd high when there is no dry spots, like a snow storm or heavy heavy rain.

4wd auto can be used daily no matter the conditions.

4wd low only when you are offroad, or need maximum pulling power, but not much turning.

Hope it all makes sense. Then there is the rear end selections....

 

[DavidNJ]

The transfer case does not include a differential. That means, in any 4wd mode the front and rear wheels turn at the same speed. This is typical in trucks because the higher loads would generate heat and require lots of force to be managed. Therefore, 4wd is only engaged when the surface is slippery. There are some steering advantages of driving the front wheels for handling on regular pavement, and for getting large amounts of power to the ground. That is not what this is designed for.

In the old days, the transfer case was shifted with a lever. Now electrically. With the various wheel speed, accelerometer, and gyro sensors used for stability control and ABS, the truck can determine when 4wd is needed. Auto 4wd runs in 2WD and simply shifts into 4wd Hi when excessive slip is detected. Since is a locked situation without a center differential, this is only going to occur when the slip is significant and probably at lower speeds, although I don't know the specific programming.

The rest of the time it is in 2WD. For most people, 2WD is where the truck will spend nearly its entire life.

4WD Hi has a 1:1 gear ratio. 4WD Lo adds an extra 2.64 reduction. That means the redline in 1st with the 5.7L and 3.92 drops from 29mph to 11mph. 2000 rpm goes from 10mph to under 4mph. It is about having the engine in its operating range when going slow in slippery or challenging conditions. For reference, the Jeep Rubicon has a 4.1:1 ratio in the transfer case.

The electrically locking rear complements the transfer case, locking both rear wheels together. Off-roaders often have a locking front differential also, and it comes standard with the Rubicon.

In those challenging, slow, slippery conditions, off-roaders often carry traction boards. May off-road/camping racks include storage for them. Shown in the picture. If you need 4WD Lo and a locking rear diff, you probably need traction boards also.

On top of that, the RAM already has traction control with what FCA calls Brake Limited Differential to act as a simulated limited-slip. A technology Porsche uses also.

Net: for most purposes, 2WD and 4WD Auto are the same and what the truck should be in.

 

[Wolf]

I know lowering the air pressure is best so the tire floats on top of the sand but 4hi? I won’t even be able to lock the rear diff in 4hi if it’ll disengage going 20mph. You’d think I’d be the other way around (disengage at 40mph in 4hi instead of 4lo)

All I know is about 12 different locals in Hawaii echoed, "4hi for the beach". I only tried that one time and got stuck in 4lo and unstuck in 4hi.

 

[John Jensen]

All I know is about 12 different locals in Hawaii echoed, "4hi for the beach". I only tried that one time and got stuck in 4lo and unstuck in 4hi.

It also depends on the driver's skill. 4lo has more torque and power and an unskilled driver will give it too much power and dig in rather than keep moving. 4hi is forgiving as it tends to keep you moving without the power to dig in. I've seen so many novices put it in 4lo and peddle to the floor = instant stuck.