2H vs 4H

jeepoch

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"ESC On" is the default operating mode when the vehicle is running. The driver may disable it manually using the Partial Off or Full Off features, which are exclusively accessed via the ESC button itself.

A full explanation of the ESC system and how it works is evident beginning on, for example, p. 152 of the 2020 Owner's Manual. It is not stated, there or elsewhere, that the act of shifting in and out of 4WD Low will have any effect on the functioning of the ESC system. If there's proof that this does in fact occur, we'll be happy to review it here.
Screenshot_20201210-193617.png


James,

In the highlighted WARNING section, first bullet:
ESC "Full Off" mode is intended for off-highway or off-road only.

Also whenever I drop into 4Lo my 'ESC Off' indicator light comes on.

Jay
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JayJay

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Just wanted to add a note - BLD (the system that brakes the wheel without traction) cannot be turned off. So even with stability control off it's still active.
Hi Kevin, the manual for my '20 JLR generally supports your comment.

" A feature of the TCS, Brake Limited Differential (BLD), functions similar to a limited slip differential and controls the wheel spin across a driven axle. If one wheel on a driven axle is spinning faster than the other, the system will apply the brake of the spinning wheel. This will allow more engine torque to be applied to the wheel that is not spinning. BLD may remain enabled even if TCS and Electronic Stability Control (ESC) are in a reduced mode."

It does say "may remain enabled" though. I wonder if the manual is wishy washy on this point because the BLD is in fact disabled when the lockers are engaged?

Later,
Johnny
 

Wabujitsu

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James,

In the highlighted WARNING section, first bullet:
ESC "Full Off" mode is intended for off-highway or off-road only.

Also whenever I drop into 4Lo my 'ESC Off' indicator light comes on.

Jay
James, you are spot-on. I too have the ”ESC Off” indicator light up when I put my Jeep in 4Lo.

I found this, which I suspect refers to the JK, but ESC is identical in the JL. It clearly indicates that ESC turns off when the vehicle is put in 4Lo. http://www.jeeclub.com/reco-814.html
 

jeepoch

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Jeff,

Thank you. The linked article from Jeep Manuals (jeeclub.com) looks like it was indeed written around circa 2015 for the JK but as you said is still likely very relevant today for the JL.

I'm just highlighting the most interesting sections here for convenience (since it's not described well in either the 2019 or 2020 JL Owner's Manuals). Hopefully this helps clarify any confusion. Maybe not.

What is very informative is that ESC, TCS and BLD (as quoted directly from the JL Owners Manual) are all in play while in both 2Hi and 4Hi but are independently applied in 4Lo (with ESC being explicitly disabled)

From the JL Owner's Manual:

Electronic Stability Control (ESC):
"This system enhances directional control and stability of the vehicle under various driving conditions. ESC corrects for oversteering or understeering of the vehicle by applying the brake of the appropriate wheel(s) to assist in counteracting the oversteer or understeer condition. Engine power may also be reduced to help the vehicle maintain the desired path."

Traction Control System (TCS):
"This system monitors the amount of wheel spin of each of the driven wheels. If wheel spin is detected, the TCS may apply brake pressure to the spinning wheel(s) and/or reduce engine power to provide enhanced acceleration and stability."

Brake Limited Differential (BLD):
"Functions similar to a limited slip differential and controls the wheel spin across a driven axle. If one wheel on a driven axle is spinning faster than the other, the system will apply the brake of the spinning wheel. This will allow more engine torque to be applied to the wheel that is not spinning."

"BLD may remain enabled even if TCS and ESC are in a reduced mode."


Now directly from the Jeeclub article:

4L Range (4WD Models)

ESC Off


"This is the normal operating mode for ESC in 4L range.

Whenever the vehicle is started in 4L range, or the transfer case (if equipped) is shifted from 4H range or NEUTRAL to 4L range, the ESC system will be in this mode. In 4L range, ESC and TCS, except for the “limited slip” feature described in the TCS section, are turned off until the vehicle reaches a speed of 40 mph (64 km/h). At 40 mph (64 km/h), the normal ESC stability function returns but TCS remains off. When the vehicle speed drops below 35 mph (56 km/h), the ESC system shuts off.

The ESC is off at low vehicle speeds in 4L range so that it will not interfere with off-road driving, but the ESC function returns to provide the stability feature at speeds above 40 mph (64 km/h). The “ESC Activation/ Malfunction Indicator Light” will always be illuminated in 4L range when ESC is off."

In summary:
It looks like the braking systems on the JL (and likely all Jeep Models) are rather sophisticated. While the Electronic Stability Control (ESC) and the Traction Control Systems (TCS) can both be placed into 'Reduced' operating modes by the driver (via cockpit pushbutton), the Brake Limited Differential (BLD) always remains active.

Furthermore in 4Lo, ESC is explicitly disabled, TSC is potentially in a reduced mode and BLD remains enabled and active.

Wow. This is really good news. While in 4Lo my Sport has more capability than I had originally thought.

Please anyone correct me if I have any of this wrong.

Jay
 
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TheRaven

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Wow. This is really good news. While in 4Lo my Sport has more capability than I had originally thought.

Please anyone correct me if I have any of this wrong.

Jay
Nope you're good. We enthusiasts make a much bigger deal out of things than we need to. All three diff types are going to be more than fine anywhere on road. The Rubicon has a little bit of an advantage in more technical off-road situations because of its lockers. But the Sahara is not going to be able to get any further than the Sport simply because of an LSD.
 

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The funny thing was when I got a loaner 2021 Sahara and it was not even close to my Rubicon 2.0T during acceleration. At first, I assumed it is 3.6L engine, when in fact it was 2.0T. The reason
I felt less power is the axle ratio. And the fact is - my 2.0T Rubicon puts way too much torque on the rear wheels in 2H with all of the following consequences. Possibly, the reason 3.6L is not experiencing it - it has less torque. I could make rear wheels spin in dry condition without even pushing accelerator all the way to the floor. Unless I have some crazy tuned Wrangler, which is possible as I am not the first owner. But there is no any mods that I could see on it and it appears to be stock. All I know the first owner has some affiliation with sheriff office in NC and retired Vet based on stickers attached to rear window.
 
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alksion

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Wow read through every page. I think I could have got unstuck yesterday in about 16 inches of snow if I would have went to 4L. Only issue was that I was stuck and could not be rolling slowly to engage 4L.
 

alksion

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I was trying to push the button for ESC in 4H to no avail.
 

alksion

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You should consider getting a Tazer JL Mini so you can lock your diffs in 4H.
Interesting. I’ll have to look into that.
 
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