Is selec track (or full time 4WD) inherently bad or weaker?

[saintpauljeff]

Thanks, but it is still in rwd at that point, I was wondering if it indicates anything when the front axle is engaged from the transfer case when it detects slip

like when slippage is detected on the rear axle so power is diverted to the front? I don't think anything is displayed on the dash in those moments

my Hummer H3 had the torsen system and also didn't actively display anything with regard to axle power

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[jsalbre]

Is there any dash light or indication when in awd that it has locked in the front axle?

The current version of Selec-trac (used in the JL and JT) doesn’t really “lock” the font axle in a traditional sense. It uses a variable electronic clutch like those used in most all wheel drive systems these days. It changes the amount of torque sent to the front axle depending on what the computer thinks you need. When you put it in 4 Hi or 4 Lo it does close the clutch 100% to work effectively like the standard Command-trac t-case.

The one thing that does happen as soon as you pull it into 4 Auto is it connects the Front Axle Disconnect (FAD). This does cause a bit of a fuel economy drop, but it wouldn’t be able to adjust front axle activation dynamically without the FAD already connected.

The one potential downside to the Selec-trac is because of its use of a clutch instead of a solid engagement like the Command-trac and Rock-trac. Some people (though a very small number) have managed to overheat the clutch when used in sand causing it to fail to engage, leaving them stuck in 2WD until it cools.

I ordered my JT with Command-trac because I was worried about that potential problem, but I now wish I’d ordered Selec-trac after seeing just how few actual problems there have been. That said, I really do wish Jeep had used something similar to the old NP242 Selec-trac, as it used a planetary center differential instead of a clutch. Old XJ Cherokees, ZJ and WJ Grand Cherokees, and KJ Libertys had this as an option. Once in “4 Full” it was always sending torque to the front, and when shifted into 4 Hi or 4 Lo it was locked in just like the other “standard” t-cases. It did have the weakness of being spring shifted though, and could get stuck While shifting until pressure was taken off.

 

[jac04]

Thanks, but it is still in rwd at that point, I was wondering if it indicates anything when the front axle is engaged from the transfer case when it detects slip

Ah, gotcha. No indication of that.

 

[jac04]

Also, when it comes to normal driving on snow covered roads, the 4HAUTO Selec-Trac simply blows away 4H Part-Time.

Selec-Trac allows the front & rear driveshafts to spin at different speeds, acting like a center differential. 4H Part-Time locks the front & rear together, forcing them to turn at the same speed, which makes cornering on slick surfaces more difficult.

 

[Gvsukids]

https://www.jeepgladiatorforum.com/...selec-trac-full-time-4wd-transfer-case.36046/

https://www.jeepgladiatorforum.com/...the-selec-trac-full-time-4wd-system-on.48468/

 

[dcmdon]

Real question, not to be argumentative, but what's the difference between shifting 4h auto on and off for mpg as you described, and switching between 2HI and 4Hi for those of us without this option? You're still moving the lever. Imo, the best usage case would be for those times when you want to just leave it on without futzing with the T-Case lever. Those without 4hi auto would still switch to 2wd once on the plowed highway, and get the same mpg gains for doing so.

In the winter in NH, its common for areas that are sun lit to be clear of snow and dry. Then you go around a corner and its shaded and its packed powder all winter.

Unexpected snow is what will get you.

In the case of using 4A, you can leave it on all the time.

I'm not advocating for putting it into and out of 4A and 2H regularly. Just on a 1100 mile trip there was some opportunity to save a bit of fuel. I've put 200 miles on it since I got home and its been in 4A the whole time.

If pulling out onto a main road from a stop sign you can punch the. throttle and it won't spin the inside rear wheel, which will cause the traction control to pull power. This is obvious in the wet to anyone who has owned a RWD pickup.

Also, If I remember correctly Jeep states a maximum speed for 4H in the 50 mph range? Please correct me if I'm wrong.

In short
4A is of no benefit driving along straight ahead on a dry highway
4A is a benefit when driving aggressively in dry roads in town
4A is a benefit when driving anytime in the wet. Particularly in town
4A is a benefit on snowy roads. especially when its a couple of days after the snow and you encounter snowy, wet and clear roads intermittently.

Again, $600. Stupid not to get it.

Also, if you've never driven or owned an AWD car you might not understand. Imagine being able to put your foot down almost any time in any condition and have no wheel spin, traction control engagement or drama of any kind.

 

[NC_Overland]

I’m pretty sure I read somewhere that it’s the same transfer case, unless it’s a Rubicon, as my 2017 Canyon. In auto 4wd it always sends 5% power to the front wheels all the time but sends more power as needed. Mine worked very seamlessly and very well. The only downside is you see a significant difference in gas mileage in auto 4wd, or at least I did on mine.

Someone please correct me if I’m wrong.

 

[dcmdon]

Is there any dash light or indication when in awd that it has locked in the front axle?

It doesn't lock. When the system detects a difference in wheel speed between the front and rear wheels it engages the clutch pack. This is the same type of system used by BMW, Nissan, VW, Audi, and Subaru on some of their AWD cars.

Once it detects that the slip has stopped the clutch pack releases. So its happening often for just very brief transient periods.

All you notice is that you can punch the throttle in a sharp turn and the truck just goes. No wheel spin as the inside wheel unloads, no traction control intervention. No drama.

Thanks, but it is still in rwd at that point, I was wondering if it indicates anything when the front axle is engaged from the transfer case when it detects slip

I don't think it indicates anything. I'll test that out this weekend. The road where our place in NH is, is a sheet of ice. Good times.

 

[NachoRuby]

Also, If I remember correctly Jeep states a maximum speed for 4H in the 50 mph range? Please correct me if I'm wrong.

There is no max speed for 4HI on JK, JLs, or JTs. There used to be back in the TJ days. Now, there's a recommened max speed for shifting into 4wd, but not for using it. You can use it up right up to the speed limiter, if you're so inclined.

In short
4A is of no benefit driving along straight ahead on a dry highway
4A is a benefit when driving aggressively in dry roads in town
4A is a benefit when driving anytime in the wet. Particularly in town
4A is a benefit on snowy roads. especially when its a couple of days after the snow and you encounter snowy, wet and clear roads intermittently.

Again, $600. Stupid not to get it.

I agree, except it would be $2600 for me haha. I wish they offered selec trac on the Manuals.

Also, if you've never driven or owned an AWD car you might not understand. Imagine being able to put your foot down almost any time in any condition and have no wheel spin, traction control engagement or drama of any kind.

I've owned tons of Subarus (and a compass), so I understand the benefits of awd. I miss AWD most often in the rain, for sure. but in snow, regular 4wd has done great (for me). I think, compared to AWD, in snow, I'm going to rate them as a dead heat. But I'm driving stick anyway, so I'm used to fumbling with a lever.

Now if this were a performance oriented car, I'd really be missing AWD more often, but the jeep is not going to take a corner like my tuned STIs did no matter how how many wheels are driven

 

[jsalbre]

I’m pretty sure I read somewhere that it’s the same transfer case, unless it’s a Rubicon, as my 2017 Canyon. In auto 4wd it always sends 5% power to the front wheels all the time but sends more power as needed. Mine worked very seamlessly and very well. The only downside is you see a significant difference in gas mileage in auto 4wd, or at least I did on mine.

Someone please correct me if I’m wrong.

I don’t know what t-case the Canyon/Colorado twins use, but the auto time t-case in JLs and JTs is the MP3022. The Rubicon with 4 auto is also the MP3022, just with a 4:1 low range.

 

[NC_Overland]

I don’t know what t-case the Canyon/Colorado twins use, but the auto time t-case in JLs and JTs is the MP3022. The Rubicon with 4 auto is also the MP3022, just with a 4:1 low range.

Hmm. I might be wrong. I was thinking it was an NV unit. Whatever it is, it’s what they used in the V6 Grand Cherokees of that year.

 

[JET_83]

Hey guys,
Great board you have here. It’s nice to see people be able to disagree and still act like adults.
So, total rookie here but I think I’m getting close to pulling the trigger. I’ve narrowed it down to a Mojave or Rubicon. Still not sure if I’m going new or a damn close used one. From the start I had the full time 4WD in my head as being one of the options I had to have. Just made sense to me if you’re anywhere that gets snow. (In my uninformed mind).
I’ve looked at hundreds of vehicles online new and used and have literally seen it on probably 5 or less.
With it being such a cheap option why do people stay away from it?

I'd much rather have full control over the 4-wheel drive system

 

[ko15870]

I ordered one with that option . For myself it is a must have as I live in an area where we get lots of lake effect snow.

I would get it for no other reason it's there when or if you need it.

 

[NachoRuby]

I'd much rather have full control over the 4-wheel drive system

You still have full control. It has all the options we have, plus one extra. It still has 2HI, 4HI, and 4LO, but it also has a 4AUTO. There's no loss of control, just more options. If I were to buy an auto, I'd get it. There's no reason not to.

 

[Devil Dog]

It doesn't lock. When the system detects a difference in wheel speed between the front and rear wheels it engages the clutch pack.

Is it a clutch pack or a viscous coupling?

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