What’s the difference between 4x4 options?

HammerHead said:

I was watching a youTube video and seen a 4x4 stuck, and the tire up in the air was spinning and the tire down in the dirt wasn't doing anything. Why is that?

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ronheater70 said:

No, your not missing anything without "Auto".. all it basically does is choose when you need it for you..

4 hi, 4 lo, all you need. I wish Ram had a decent locker, That GM one is good, I liked the Electronic locker in my ford I traded for the Ram. The Anti Spin Diff in the Ram is a joke.

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HammerHead said:

Got my first 4x4 and it has 4High and 4Low. No 4Auto option; whats the difference between the three? Am I missing anything with no 4Auto?
Its not a Ram either, went with the GMC 2500HD, 410 Gears and locking rear diff. I know I'm not a Ram owner anymore but this has been my home forum for the last 4 years.

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HammerHead said:

I diden't know 4x4's had that problem. I just assumed when in 4x4 mode all wheels get some power.

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ColdCase said:

If all wheels have traction, yes. If not then no unless you have a locker, limited slip diff, or brake traction control to divert some power from the wheel thats spinning to the one thats not. With a 4x4 without axle traction control, you can get one front and one rear wheel spinning and go nowhere but fast. But at least there are two wheels spinning. A 4x2 will only spin one wheel without axle traction control.

Some Auto 4x4s don't lock the axles until there is some spin, undesirable in many situations.

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MdMassey said:

I see your original question wasn't answered completely. So here's the skinny.

4hi puts your truck into 4wd mode with no extra gear reduction. This will allow you to travel at freeway speeds and below with the extra traction given by it being in 4wd mode.

4lo grants you more torque by the way of extra gear reduction in the transfer case. This will help you in tough terrain but limit your speed to around 20mph. Not for use on the road. GM requires you to shift the truck into neutral and be rolling at roughly 1mph to engage 4lo. Also 4lo will not help you get unstuck if you are already stuck... it's not a save my ass mode.
I hope this answers your questions about what 4wd modes are... oh and Auto mode simply lets a computer decide between 2wd and 4wd for you... it won't select 4lo ever.

Now to the diffs.
An open diff has no mechanism to lock the axles together. This is fine for normal driving but get into slippery stuff and off road it isn't much help. With this type of diff if one tire loses traction all the torque will be transferred to that tire. The tire with traction will not move.

Posi, Detroit Locker, Limited Slip, Torson and many others are ways to lock both axles together when one side loses traction. Each do it in different ways but the end results are the same. Which one is better... I'm not gonna touch that one, I don't want to write a book.

Now to the locking diff or a locker. This is a mechanical device inside the diff that binds the axles together as one. Torque is transferred equally to both wheels and there is no differential action at all. This could be an Air Locker (ARB is one example) or electric (Factory Power Wagon has this). This will help you through loose terrain but will cause control issues on slippery ground when turning. Use this when you lose traction but turn it off when your footing is better.

The last thing I will talk about here is brake controlled traction assist. I'm not sure if GM or Ford does this but I know Ram and Jeep both do this. This system will allow an open diff to act like a posi by applying brake friction to only the wheel that is losing traction so the diff will still transmit torque to both wheels. This system works ok but it's not a replacement for a Locker.

Hope this helps.

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MdMassey said:

I see your original question wasn't answered completely. So here's the skinny.

4hi puts your truck into 4wd mode with no extra gear reduction. This will allow you to travel at freeway speeds and below with the extra traction given by it being in 4wd mode.


To add to what MdMassey said:
with a part time (4hi and 4lo only) 4x4 system, you do not want to use 4wd on high traction surfaces such as dry paved roads. Doing so will cause binding in the drive line.
Icy conditions can be problematic for part time 4x4 as well. On ice, with 4x4 engaged, it is much easier for the front wheels to loose traction which will cause a loss of steering control.

Mixed condition roads(mix of dry and snow/ice covered) is where the full time 4x4 systems (auto 4x4) have an advantage.

That being said, I survived many Midwest winters with part time 4x4 by simply putting weight in the bed, and only engaging 4x4 when pulling someone out of a ditch, or going off pavement.




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MdMassey said:

I see your original question wasn't answered completely. So here's the skinny.

4hi puts your truck into 4wd mode with no extra gear reduction. This will allow you to travel at freeway speeds and below with the extra traction given by it being in 4wd mode.

4lo grants you more torque by the way of extra gear reduction in the transfer case. This will help you in tough terrain but limit your speed to around 20mph. Not for use on the road. GM requires you to shift the truck into neutral and be rolling at roughly 1mph to engage 4lo. Also 4lo will not help you get unstuck if you are already stuck... it's not a save my ass mode.
I hope this answers your questions about what 4wd modes are... oh and Auto mode simply lets a computer decide between 2wd and 4wd for you... it won't select 4lo ever.

Now to the diffs.
An open diff has no mechanism to lock the axles together. This is fine for normal driving but get into slippery stuff and off road it isn't much help. With this type of diff if one tire loses traction all the torque will be transferred to that tire. The tire with traction will not move.

Posi, Detroit Locker, Limited Slip, Torson and many others are ways to lock both axles together when one side loses traction. Each do it in different ways but the end results are the same. Which one is better... I'm not gonna touch that one, I don't want to write a book.

Now to the locking diff or a locker. This is a mechanical device inside the diff that binds the axles together as one. Torque is transferred equally to both wheels and there is no differential action at all. This could be an Air Locker (ARB is one example) or electric (Factory Power Wagon has this). This will help you through loose terrain but will cause control issues on slippery ground when turning. Use this when you lose traction but turn it off when your footing is better.

The last thing I will talk about here is brake controlled traction assist. I'm not sure if GM or Ford does this but I know Ram and Jeep both do this. This system will allow an open diff to act like a posi by applying brake friction to only the wheel that is losing traction so the diff will still transmit torque to both wheels. This system works ok but it's not a replacement for a Locker.

Hope this helps.

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UnsatFC said:

What models have the brake controlled traction assist??

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gypsy400 said:

They all do.. traction and stability control is activated by braking certain wheels and/or cutting throttle.. so if you want to spin tires in the mud, turn it off.

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muddy12 said:

Only thing wrong with that is that even when you push the off button, once wheel speed hits about 40mph, traction and stability control re activate and cut the throttle.


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