KJ 4WD systems - which one is in which year??

TurboGoKart · **Posted:** Thu Oct 25, 2012 10:05 pm

I've been reading around, but still need a little clarification.

1. Part time 4WD means that the front and rear axles are locked giving basically equal power to both. The disadvantage to this is you cannot use this mode on dry pavement.
2. Full time 4WD means that there is an open differential between the front and rear axles, giving more power to whichever axle is spinning. The advantage to this is you can use full time 4WD on dry pavement to avoid crow hopping/tire scrubbing etc.

Reading up on which systems those are, I found that Command-trac offers #1. Selec-trac offers #1 and #2. In my mind, #1 would be better off road, correct? Now, the Selec-trac II which basically does away with the part time, is what they switched to for the KK, yes?

So if I wanted to find a Liberty model that has part time AND full time 4WD, which model would I need to look at? Or does the KK (2008 model) still have part time 4WD, or did they do away with it?

tjkj2002 · **Posted:** Thu Oct 25, 2012 10:21 pm

Command Trac-231/241 t-case..........

2wd
Part time 4wd
"N"
4low

Select trac-242 t-case............

2wd
Full time 4wd
Part time 4wd
"N"
4low

Part time 4wd(and 4low) locks the front and rear driveshafts to amke them spin the same,does not lock the diffs,and can not be used on high traction surfaces and yes that includes wet pavement.

Any of those t-cases are found on any KJ from '02 all the way to '07.No 242 behind a manual trans though and the 241 t-case was only offered behind the 6 speed manual.

The KK went totally different in a sense,command trac II is the same but the select trac II does not have part time 4wd and both are electronicly shifted.

TurboGoKart · **Posted:** Thu Oct 25, 2012 10:28 pm

Ok cool. So whats the easiest way to tell which t-case it has? By looking at the 4WD selector? Or are the t-cases labelled somewhere else on the vehicle (a sticker or similar). I'm looking to buy one, and trying to decide between an 07 and 08, but mostly depends on which t-case the 08 has, because I don't think I like the idea of only having the full time option.

tjkj2002 · **Posted:** Thu Oct 25, 2012 10:31 pm

The shifter is the easiest way,4 spots and it's the command trac,5 spots and it's the select trac.The KK's have a small switch in the center console and do not use NV/NP t-cases anymore but MP t-cases.There is a tag on the t-case also that tells which case it is.

TurboGoKart · **Posted:** Thu Oct 25, 2012 10:56 pm

Awesome! Thank you! So on the KK's then it'd be the difference between 3 and 4 settings? I've seen them with "2WD, 4WD AUTO, and 4WD LOW" which I'm guessing would be the Selec-trac II. So if it were the Command-trac II it'd have another setting?

Am I just splitting hairs here, or is there really a decent difference between locking the front and rear axles vs. having the open diff?

TwoBobsKJ · **Joined:** Fri May 11, 2012 8:03 pm **Posts:** 463

You're starting to mix things up a bit.

Both the KJ and the KK will have open diffs - though some KJ models would have the TrakLock diff in the rear which is not a locking differential but kind of a 'reduced spin' diff. And as quickly as the TrakLock wears out any KJ you look at will have open diffs even if it came from the factory with the 'trash-lock.' Some KK's may have the brake lock system which applies brakes to the spinning wheel to send power to the wheel with traction. Kind of like an auto locker but not a true, locked differential.

Open diffs mean that - even if in one of the 4WD modes - the tire with least traction on either axle will spin, for instance in mud or if the tire is off the ground. So 4WD is really a misnomer cuz at any one time only one wheel on each axle is really powered if the other wheel on the axle is on a very slippery surface.

As for the transfer case:

For off-road the Part Time or 4Lo functions are best. Part Time enables you to run normal speed (slippery surfaces ONLY) while in 4Lo you can go no faster than about 15mph. In Part Time and 4Lo the front and rear axles spin at the same speed - no differentiating between them, hence the crow hop and binding on dry or high traction surfaces. The differentials on each axle are still open unless you put a locker in them.

The SelecTrac Full Time can be run 12 months a year on any road surface. Great for driving around town on a snowy day or to just keep the transfer case nice and lubed up (a good idea to do with the SelecTrac transfer case) for when you really need it off road.

As for the KK selector: If it only shows 2WD, 4WD Lock and 4WD Low it is the CommandTrac II case and functions like the KJ's CommandTrac Part Time case. If the KK's selector shows 2WD, 4WD Auto and 4WD Low it is the SelecTrac II and functions similarly to the KJ's SelecTrac Full Time transfer case. You can switch to 4WD Auto any time and drive it on any surface - dry, wet, snow, etc - with no problems.

I have the SelecTrac Full Time case in my '03 KJ and like it's flexibility. It's finicky (tires MUST be the same size) but it has served me well on the street and off-road. It has 5 positions on the shift handle (2WD, Part Time, Full Time, Neutral, 4Lo.) The CommandTrac has 4 positions (2WD, Part Time, Neutral, 4Lo.)

Here's a link to Jeep's explanation of the SelecTrac II system in the KK: http://www.jeep.com/en/4x4/#CommandTrack2,SelecTrac2,

Bob

TurboGoKart · **Posted:** Fri Oct 26, 2012 1:06 pm

Thanks for the explanation Bob! That was exactly what I was looking for! Very much appreciated.

lfhoward · **Posted:** Fri Oct 26, 2012 1:44 pm

When I was hunting for a used KK to buy, most of the online ads didn't specify which 4 wheel drive system each Jeep had. So if there were pictures in the ad, I zoomed in to see the 4 wheel drive switch. As TwoBobsKJ noted, if it said 2WD, 4WD LOCK, and 4WD LOW it was CommandTrac II, and if instead of "LOCK" it said "AUTO", then it was SelecTrac II. The CommandTrac II system is by far more common than the SelectTrac II.

lfhoward · **Posted:** Fri Oct 26, 2012 1:48 pm

Here's another good tool when searching for a vehicle. If you know the VIN, you can use this VIN Decoder to see the build sheet that will tell you which options a Jeep rolled out of the factory with, including the type of 4 wheel drive system. The site allows a limited number of searches per day if you don't pay, but if you spread out your VINs over several days and only use it for Jeeps that you're seriously interested in, you won't need to worry about paying for access.

http://www.compnine.com/vid.php?

TurboGoKart · **Posted:** Fri Oct 26, 2012 2:21 pm

Thanks, that link is very helpful. I went and looked at this particular KK today, and it does have the Command-trac II. Needs new tires pretty soon, but other than that it's in good condition. No tow package, so no extra trans cooler, but those really aren't hard to put in aftermarket if I want to go that route.

KJ 4WD systems - which one is in which year??

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