When are you using 4H and 4L on your Wrangler?

MrMischief

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If you need 4hi then you should not be running 70! 😁
In my TJ I've had the cruise set at 80 mph pulling it in and out of 4H. Going across Wyoming the road can be clear on a sunny day but where the snow drifts across during the day and melts it then refreezes as the sun goes down. So cruise at 80 mph, see one of these ice traps, tap the brake to get cruise off as pulling into 4H and then a constant throttle across the ice, once clear kick it back to 2H and hit resume on the cruise. Rinse and repeat for the entirety of I-25 in WY. Been doing this for years in TJs, haven't blown anything up or hit the ditch yet. I'd do the same in the JL just haven't been in that situation with it yet.
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Sital

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In winter here in New England (and just talking about pavement), I'm pretty much always in 2H. On the rare occasion have I needed 4H. I thought I'd be using my Sahara in 4H Auto, but I've ended up just keeping it in 2H. I've never needed 4H in rain.
 

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In winter here in New England (and just talking about pavement), I'm pretty much always in 2H. On the rare occasion have I needed 4H. I thought I'd be using my Sahara in 4H Auto, but I've ended up just keeping it in 2H. I've never needed 4H in rain.
Likely it is the LSD pulling you through in 2WD in the snow.

While I can’t say I’ve needed 4A in the rain, I find it provides a more planted driving. Especially here in the PNW, where we can measure rain in weeks.
 

sentience

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For the JL, I recall the max high speed for 4H was 55 mph, and 4L was 25 mph.

Since I don’t know precisely when 4H Auto is activated in 4H, I don’t trust it and leave it off. Maybe there’s an idiot light I missed for it.

I’ll throw it into regular 4H if there is more than a foot of water, or notable snow/ice on road. (And use it as needed off road). 2L for strictly off road “oh shit” situations.

Overall, the stock set of all terrain tires are grippy enough to leave it in 2H for most road conditions.
 

Reinen

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There are exceptions but in general:
  • 2WD
    • Pavement in all conditions other than snow/ice
    • well maintained mostly flat dirt roads
  • 4WD Auto
    • Snow covered pavement up to 6", especially partially cleared snowy pavement
    • I usually avoid using this for dirt roads as there is always a degree of slip on dirt and repeated automatic engagement of 4WD can cause clutch overheating.
  • 4WD HI
    • Less than well maintained dirt roads
    • dirt roads with significant inclines
    • mild off road
    • snow greater than 6" on pavement
    • snow on mud/dirt
    • Hard sand
    • Note:
      It's important to know that in light snow on pavement, 4WD can put you into a skid during turns and send you off the road. If you don't have 4WD Auto, you're better off in 2WD and only use 4WD HI if you can't gain forward traction.
  • 4WD LO
    • Poorly maintained dirt roads
    • Dirt roads with severe inclines
    • Soft sand
    • moderate and up off-road
In regard to traction control, it's important to remember that it's designed for pavement. The slipping and sliding inherent to dirt roads and off-road means you will be fighting traction control more than it will be helping you. That's why you can turn it off. It's a bit counter intuitive as traction control sounds like something you'd want off road but you don't. Think of it as "Pavement Traction Control" and it will make more sense.
 

flyer92

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In regard to traction control, it's important to remember that it's designed for pavement. The slipping and sliding inherent to dirt roads and off-road means you will be fighting traction control more than it will be helping you. That's why you can turn it off. It's a bit counter intuitive as traction control sounds like something you'd want off road but you don't. Think of it as "Pavement Traction Control" and it will make more sense.
Thanks for the great explanation, as well as the info regarding traction control. While this feature is automatically disabled in 4L, I've always been curious why the same thing doesn't happen in 4H. Down here in SoCal, I never drive my 2-door Sport in snow, but was more curious about this issue for off-road driving (sand, gravel, rocky trails, desert overlanding, etc.). After disabling and enabling TC with 4H, I still can't determine what's better. Any recommendations/advice?
 

Reinen

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Thanks for the great explanation, as well as the info regarding traction control. While this feature is automatically disabled in 4L, I've always been curious why the same thing doesn't happen in 4H. Down here in SoCal, I never drive my 2-door Sport in snow, but was more curious about this issue for off-road driving (sand, gravel, rocky trails, desert overlanding, etc.). After disabling and enabling TC with 4H, I still can't determine what's better. Any recommendations/advice?
As with all things, it's never really a hard "turn it off/on". It depends a lot on the terrain and your driving style. But it predominantly works by applying individual brakes and cutting throttle. Sometimes that's exactly what you don't want, where you need wheel spin to get you through slipping. Sometimes someone might like it as it keeps you from going "too far" and firmly rooted. Depends on the terrain and driver.

Personally, I tend to turn it off when off road. I can stay rooted if I want, and punch it when I need to.
 

bigbaozi

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For the JL, I recall the max high speed for 4H was 55 mph, and 4L was 25 mph.

Since I don’t know precisely when 4H Auto is activated in 4H, I don’t trust it and leave it off. Maybe there’s an idiot light I missed for it.

I’ll throw it into regular 4H if there is more than a foot of water, or notable snow/ice on road. (And use it as needed off road). 2L for strictly off road “oh shit” situations.

Overall, the stock set of all terrain tires are grippy enough to leave it in 2H for most road conditions.
No max speed on 4H that I'm aware of, the manual specifies shifting between 0-45mph. There's some practical matter there on how fast are you willing to go on a slippery road that justifies having 4H enabled. 25 is the 4L limit in the manual, again courage willing I guess?

The 4A system won't shift until it detects some slip, good idea for snow, not so good if you actually want the 4WD system on.
 

bigbaozi

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Thanks for the great explanation, as well as the info regarding traction control. While this feature is automatically disabled in 4L, I've always been curious why the same thing doesn't happen in 4H. Down here in SoCal, I never drive my 2-door Sport in snow, but was more curious about this issue for off-road driving (sand, gravel, rocky trails, desert overlanding, etc.). After disabling and enabling TC with 4H, I still can't determine what's better. Any recommendations/advice?
4H, higher speeds, more likely to need stability or traction control to intervene and keep your butt out of a skid. Plus you kind of expect some wheel spin in 4L, right? You shouldn't be crawling in 4H.
 

Reinen

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4H, higher speeds, more likely to need stability or traction control to intervene and keep your butt out of a skid. Plus you kind of expect some wheel spin in 4L, right? You shouldn't be crawling in 4H.
There is also only so much traction control can do in 4H. Your front & rear driveshafts are locked which means in a turn, at least one of your wheels needs to skid a little bit. Exactly what you don't want on slick pavement.
 

try4321

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4A all the time. 4H off pavement. haven't tried 4L yet.

But I have yet to figure out how 4H-Auto works. They say front axel is engaged but power is send to rear excel and it automatically sends power to front axel when there is traction loss. What does that mean? Is the transfer case locked or not?

If front axel get power only on traction loss then why does it do better on 0-60 on 4H-Auto. In one of the YouTube video is said 4H-Auto is 70% rear and 30% front power. Haven't read it in any official documentation though. I have gone through a bunch of forum threads and YouTube videos and of course manual/fliers.

Does this table look ok?
Screen Shot 2021-06-14 at 2.47.15 PM.png
 

bigbaozi

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There is also only so much traction control can do in 4H. Your front & rear driveshafts are locked which means in a turn, at least one of your wheels needs to skid a little bit. Exactly what you don't want on slick pavement.
It can do the same things it does in 2H, hit individual brakes or cut throttle input. Your differentials aren't locked, they still shift power left/right depending on conditions.
 

Reinen

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It can do the same things it does in 2H, hit individual brakes or cut throttle input. Your differentials aren't locked, they still shift power left/right depending on conditions.
Yes, but since the transfer case is locked in 4WD (as opposed to a center differential in AWD) one wheel in the front must turn at the same rate as one wheel in the back. In a turn, none of the tires travel the exact same distance.
 

bigbaozi

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Yes, but since the transfer case is locked in 4WD (as opposed to a center differential in AWD) one wheel in the front must turn at the same rate as one wheel in the back. In a turn, none of the tires travel the exact same distance.
Well, that's the reason you are only supposed to use 4WD on slippery surfaces. It doesn't really stop the traction or stability control from working on those slippery roads.
 

Reinen

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Well, that's the reason you are only supposed to use 4WD on slippery surfaces. It doesn't really stop the traction or stability control from working on those slippery roads.
It's also the reason why 4WD is detrimental on very slippery surfaces. It will force a loss of traction and skid of one tire in every turn. This places an increased lateral demand on the remaining 3 non-skidding tires to hold the turn. I'm not saying it stops traction or stability control from working. However the demand on these systems is increased as one tire is always being torn into a skid in a 4WD turn and traction/stability control systems are inhibited because it's geometrically impossible to keep all 4 tires from skidding with 4WD engaged. This is the exact reason why AWD is better on snowy roads than 4WD. 4WD vehicles are much more likely to experience a drive-off accident than AWD.
 
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