Selec-Trac Full Time 4WD Sys

ED2018

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Can i drive with the 4H Auto all the time in all roads and all speeds including highways? this the way i read how Jeep describe the Auto option available in Sahara/Moab.
i like how the jeep handle with the 4H Auto i understand the downside will be on more fuel but its a jeep and will spend on gas anyway.

just to make sure that this option will not cause any damages with daily high speed driving.
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Covfefe

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Can i drive with the 4H Auto all the time in all roads and all speeds including highways? this the way i read how Jeep describe the Auto option available in Sahara/Moab.
i like how the jeep handle with the 4H Auto i understand the downside will be on more fuel but its a jeep and will spend on gas anyway.

just to make sure that this option will not cause any damages with daily high speed driving.
Yes
 

Columbus104

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Can i drive with the 4H Auto all the time in all roads and all speeds including highways? this the way i read how Jeep describe the Auto option available in Sahara/Moab.
i like how the jeep handle with the 4H Auto i understand the downside will be on more fuel but its a jeep and will spend on gas anyway.

just to make sure that this option will not cause any damages with daily high speed driving.
You’re fine leaving it on. This was designed as a set-it-and-forget-it option. The fuel economy sacrifice appears be relatively small: .5-1 mpg.
 

gibson

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Hi guys ! silly question maybe sorry, but it is not 100% clear in my mind.
I currently have a 2000 Chevy Blazer LT fitted with a Auto 4WD Mode.
It keeps the transfer case in two-wheel drive until slip occurs. Yet it reacts instantly to loose gravel or icy pavement, shifting seamlessly into four-wheel drive. So it is not a permanent 4wd as I used to have 5 years ago on my Landrover Defender.
What is the situation on the Wrangler Sahara in 4H Auto ? Do the front wheels engage only if a slip occurs (as my Blazer does when the system works...Stupid electric buttons on the dashboard...) ? Or does the Wrangler become in this 4H Auto Mode a full time permanent 4WD, which would be very cool (as a Audi Quattro, a Defender or a Subaru Impreza) ? Meaning that power/torque is permanently distributed to the front wheels with a certain ratio ?
 

seguerski

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per Jeep: "The Selec-Trac® 4x4 System features a full-time mode that will automatically switch from 2WD to 4WD when conditions dictate. Relying on internal wheel speed and traction control sensors, Selec-Trac makes driving in uneven terrains and inclement weather safer and smoother while delivering superior efficiency when four-wheel drive isn’t needed."
 
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seguerski

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I'm sure someone else did a write up on these but here's the differences between the different versions of Selec-Trac:
  • Selec-Trac I
    • NP228 and NP229 transfer cases
      • 1983-1991
      • the 2WD-to-4WD modes were controlled via a vacuum switch on the dashboard. The Hi-N-Lo range selection was still performed using a shift lever on the console
      • The NP228 differs from the NP229 by not having the viscous coupling in 4WD Hi mode, reverting to a simpler open center differential. Both transfer cases still lock the center differential in 4WD Lo mode
    • NP242 transfer case
      • 1987-2007
      • The shifter has modes 2WD - 4WD Hi Part-Time - 4WD Hi Full-Time - N - 4WD Low. There is a center differential that is open in 4WD Hi Full-Time mode and distributes torque 48/52% front-to-rear. This mode can be used on dry pavement or slippery surfaces with only a small fuel mileage penalty compared to 2WD mode. In 4WD Hi Part-Time and 4WD Low, the center differential is mechanically locked, so these modes are for slippery surfaces only. Overall, this system functions very much like the NP228 transfer case above, just with all of the mode and range controls via a single, console-mounted shift lever
  • Selec-Trac II
    • MP3022 transfer case
    • 2008-2012
    • The switch controls the 4WD mode with options of 2WD - 4WD Auto - N - 4WD Low. The MP3022 transfer case uses an electronically controlled clutch pack to bias torque from 100% rear to 50/50% front/rear
    • The transfer case has no center differential, so power can only be supplied to the front axle when the rear wheels begin to slip
Wrangler JL Sahara's implementation is more in-line with the Selec-Trac II implementation as there is no open center differential
 

gibson

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per Jeep: "The Selec-Trac® 4x4 System features a full-time mode that will automatically switch from 2WD to 4WD when conditions dictate. Relying on internal wheel speed and traction control sensors, Selec-Trac makes driving in uneven terrains and inclement weather safer and smoother while delivering superior efficiency when four-wheel drive isn’t needed."
So, on 4H Auto Mode, if I understand correctly, the car is running in 2wd if the pavement is dry right ? No torque at all sent to the front wheels ?
Front wheels engage only if a slip occur ?
If this is correct, I must say that what's written on the transfer case shifter is a bit misleading: 4H part time is in fact a position where the torque is distributed full time to the 4 wheels. On the contrary, 4H Auto Mode (if it is what I have on my Blazer) is not a full time permanent awd position. It's basically 2wd that shifts automatically in 4wd when a slippery situation occurs.
Is it efficient ?
Has any Sahara owner already tried it during heavy rains ?
Does the system send the torque to the front wheels quickly enough when needed ? On the Blazer, it is not that good. You can actually feel the time lag.
On my ex Landrover Defender, i was always in 4WD which is way more secure I think under heavy rains.

Thx in advance for your comments and sorry if my english is not perfect. (I'm a french guy living in Italy).
 

seguerski

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Yes, 4H Auto (Four-Wheel Drive Auto High Range):

For variable driving conditions, the 4WD AUTO mode can be used. In this mode, the front axle is engaged, but the vehicle's power is sent to the rear wheels. Four-wheel drive will be automatically engaged when the vehicle senses a loss of traction. Because the front axle is engaged, this mode will result in lower fuel economy than the 2WD mode.

If no slipping is occurring, the vehicle will run in 2wd.

It's somewhat of a letdown as my 2004 Jeep Grand Cherokee did in fact have a 4wd Full-Time mode (via the older Selec-Trac transfer case), which powered all four wheels all the time (48%/52% torque split).
 
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palmor

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So, on 4H Auto Mode, if I understand correctly, the car is running in 2wd if the pavement is dry right ? No torque at all sent to the front wheels ?
Front wheels engage only if a slip occur ?
If this is correct, I must say that what's written on the transfer case shifter is a bit misleading: 4H part time is in fact a position where the torque is distributed full time to the 4 wheels. On the contrary, 4H Auto Mode (if it is what I have on my Blazer) is not a full time permanent awd position. It's basically 2wd that shifts automatically in 4wd when a slippery situation occurs.
Is it efficient ?
Has any Sahara owner already tried it during heavy rains ?
Does the system send the torque to the front wheels quickly enough when needed ? On the Blazer, it is not that good. You can actually feel the time lag.
On my ex Landrover Defender, i was always in 4WD which is way more secure I think under heavy rains.

Thx in advance for your comments and sorry if my english is not perfect. (I'm a french guy living in Italy).
I've driven other vehicles with this type of AWD system and it's never been an issue. It finally snowed in the NE US and I did some tests of pulling out of a parking lot into a snow covered road (empty, no traffic) a little bit quicker (not crazy but not careful either) then I normally would to see how fast the front wheels would kick in (aka I shouldn't be fishtailing the backend if it transfers the power fast enough) and like other vehicles I've driven the transition was seem-less, I did not induce a 180 coming out of the parking lot :)

My last vehicle was a full time AWD (Audi S4) with a 40 front/60 rear split but it would transfer power when needed. That car would fishtail more in this scenario then the jeep so I'm perfectly happy with the performance.
 

stewartld

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So, on 4H Auto Mode, if I understand correctly, the car is running in 2wd if the pavement is dry right ? No torque at all sent to the front wheels ?
Front wheels engage only if a slip occur ?
If this is correct, I must say that what's written on the transfer case shifter is a bit misleading: 4H part time is in fact a position where the torque is distributed full time to the 4 wheels. On the contrary, 4H Auto Mode (if it is what I have on my Blazer) is not a full time permanent awd position. It's basically 2wd that shifts automatically in 4wd when a slippery situation occurs.
Is it efficient ?
Has any Sahara owner already tried it during heavy rains ?
Does the system send the torque to the front wheels quickly enough when needed ? On the Blazer, it is not that good. You can actually feel the time lag.
On my ex Landrover Defender, i was always in 4WD which is way more secure I think under heavy rains.

Thx in advance for your comments and sorry if my english is not perfect. (I'm a french guy living in Italy).
I have it and used it on snow...the 4H auto feels very like my BMW X5 in terms of how it reacts to poor traction. I think it brakes the slipping wheels but I'm not 100% on that....
 

mwilk012

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I have it and used it on snow...the 4H auto feels very like my BMW X5 in terms of how it reacts to poor traction. I think it brakes the slipping wheels but I'm not 100% on that....
That's not the Selec-trac, thats the brake-lock differential system that all wranglers with open differentials have.
 

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So, on 4H Auto Mode, if I understand correctly, the car is running in 2wd if the pavement is dry right ? No torque at all sent to the front wheels ?
Front wheels engage only if a slip occur ?
If this is correct, I must say that what's written on the transfer case shifter is a bit misleading: 4H part time is in fact a position where the torque is distributed full time to the 4 wheels. On the contrary, 4H Auto Mode (if it is what I have on my Blazer) is not a full time permanent awd position. It's basically 2wd that shifts automatically in 4wd when a slippery situation occurs.
Is it efficient ?
Has any Sahara owner already tried it during heavy rains ?
Does the system send the torque to the front wheels quickly enough when needed ? On the Blazer, it is not that good. You can actually feel the time lag.
On my ex Landrover Defender, i was always in 4WD which is way more secure I think under heavy rains.

Thx in advance for your comments and sorry if my english is not perfect. (I'm a french guy living in Italy).
I'm in south florida - during raining season(& it rains & rains & floods) I use it all the time. Does it work - it not only works - its great!! Its one of the reasons I went with the sahara. I also got the option that gives you the limited slip & the 44 rear axle. Go anywhere & PARK anywhere.
 

Joeymon1

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I have it and used in the snow, ice, and deep snow. It works great. As far as I'm concerned its the best for use on the road in any condition where you may experience loss of traction. No worries about forgetting to shift out of 4wd. Mine shifts easily in and out.
Use 4 wheel high and low off road.
 

gibson

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I'm in south florida - during raining season(& it rains & rains & floods) I use it all the time. Does it work - it not only works - its great!! Its one of the reasons I went with the sahara. I also got the option that gives you the limited slip & the 44 rear axle. Go anywhere & PARK anywhere.
thx
 

gibson

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I have it and used in the snow, ice, and deep snow. It works great. As far as I'm concerned its the best for use on the road in any condition where you may experience loss of traction. No worries about forgetting to shift out of 4wd. Mine shifts easily in and out.
Use 4 wheel high and low off road.
thx
 
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