Types of 4x4 and how they work? - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Cherokee & Comanche Forums > XJ Cherokee Technical Forum > Types of 4x4 and how they work?

FS: Wrangler RGB Multicolor Fog Light LEDs: Awesome EffectSavvy Aluminum Gas Tank SkidFS: 2007-2013 Jeep Wrangler "HALO" Angel Eye Kit

Reply
Unread 03-06-2013, 11:10 AM   #1
aldersonfilm
Registered User
1998 TJ Wrangler 
 
Join Date: Jun 2012
Location: Pasadena, CA
Posts: 177
Types of 4x4 and how they work?

Everyone always take for granted that if you pull the lever in the center console, all 4 wheels start turning, but I'm curious if anyone knows the actual mechanics behind the different types of 4x4.

For example, I have Select-trac, so I've got 4-low, 4x4 part time and 4x4 full time. How do all of these differ? I'm especially curious about how 4x4 full time works.

aldersonfilm is offline   Reply With Quote
Unread 03-06-2013, 01:17 PM   #2
buildin1XJ
Web Wheeler
1999 XJ Cherokee 
 
Join Date: Oct 2011
Location: Knoxville, Tn.
Posts: 1,568
When I got my first XJ with selec-trac that confused me a little also. Part time position is meant to be used only when road conditions or off road conditions require the use of 4WD and are never to be used on dry paved roads. Full TIME 4 Hi can be used even on dry surfaces wet roads patchy snow covered and such because the front and rear axles are allowed to turn at different speeds and the owners manual actually states that full time can be used year round. 4 low is to be used when you need either more pulling power or decreased speed and is to never be used on dry pavement. When engaged in 4 low or Part time the front and rear wheels are turning at the same speed.
buildin1XJ is offline   Reply With Quote
Unread 03-06-2013, 02:48 PM   #3
Hudson
Registered User
1999 XJ Cherokee 
 
Join Date: Mar 2010
Location: New Milford, Connecticut
Posts: 782

Part Time - T-Case doesn't compensate for inner wheel spinning faster when cornerning. Will bind up T-case if used on Dry pavement. Needs to be used on dirt or slippery surfaces so the wheels can slip.

Full Time - Opposite of Part-Time. T-case compensates for inner tire spinnning faster, and can be used on all sorts of surfaces. Can drive around all the time in 4 full time with no ill affects.

4 Low - Gears the Transfer case down into a really low "crawling gear". Gives WAY more torque and is better for offroading.
__________________
Live To Die. You're Not Going To Get Out Of This One Alive.

Build Thread - http://www.ausjeepoffroad.com/forum/showthread.php?t=121903
Hudson is offline   Reply With Quote
Unread 03-06-2013, 03:43 PM   #4
Kettles
Registered User
2001 XJ Cherokee 
 
Join Date: May 2009
Location: Louisville, Kentucky
Posts: 4,178
Not exactly. The inner and outer wheel differentiating is done in the axle differential. In part-time the front and rear axles are locked together with no differential, therefore the average speed of the front axle and the rear axle must be the same. The problem with part time is that the rear axle and the front axle take different arcs in a corner (rear being smaller), so you get a binding similar to having a locker in an axle. The surface must be slippery enough to allow something to slip, so nothing breaks.

In full time there is a differential in the transfer case allowing the front axle and rear axle to travel at different speeds. The problem with full time is that like an open differential you can have 1 side spinning and the other stationary (in this case, the front or rear output are the "sides"). Now combine that with open differential in the axles you can get stuck with one wheel spinning like in 2wd. In part-time, at least one wheel on each axle have to be moving, so its harder to get stuck.

Edit: Fixed it up a bit when I got to a computer.
__________________
_=====o000o
//__l_l_,\____\,____
l_--\_l__l_/--|lllll|
_.(o)_)__.(o)_)--o-)_)
"Dee", a Patriot Blue 2001 Cherokee Sport 4.0L High-Output Pictures Build Thread
The Rocket Sheep
"Live Free Or Die; Death Is Not The Worst of Evils." -General John Stark
Quote:
Originally Posted by speedbucket View Post
perfect depends on how far away you are when you look at it:D
Quote:
Originally Posted by Millermagic View Post
It's a 4.0 ... as long as there's something in the crank case that isn't coolant I'm sure it will still run forever.
Kettles is offline   Reply With Quote
Unread 03-06-2013, 04:03 PM   #5
aldersonfilm
Registered User
1998 TJ Wrangler 
 
Join Date: Jun 2012
Location: Pasadena, CA
Posts: 177
Well explained Kettles! Thanks!
aldersonfilm is offline   Reply With Quote
Unread 03-06-2013, 04:36 PM   #6
Kettles
Registered User
2001 XJ Cherokee 
 
Join Date: May 2009
Location: Louisville, Kentucky
Posts: 4,178
Im at a computer now.
In summary
Full-time: differential action in the transfer case

Part-time: Locked differential in transfer case

4-low is just a part-time setting with a reduced gear ratio.

So if your off-roading, part-time is what you want to use. If your driving down the highway/street and your paranoid you might need more traction (or to help balance braking), full time is better. You can use full time, full time (as the name implies) if you want to, its effectively all-wheel drive. Generally the NP231 (command-trac transfer case) is more desirable due to significantly more aftermarket support. The NP242 (select-trac) I think hangs a tad lower.
__________________
_=====o000o
//__l_l_,\____\,____
l_--\_l__l_/--|lllll|
_.(o)_)__.(o)_)--o-)_)
"Dee", a Patriot Blue 2001 Cherokee Sport 4.0L High-Output Pictures Build Thread
The Rocket Sheep
"Live Free Or Die; Death Is Not The Worst of Evils." -General John Stark
Quote:
Originally Posted by speedbucket View Post
perfect depends on how far away you are when you look at it:D
Quote:
Originally Posted by Millermagic View Post
It's a 4.0 ... as long as there's something in the crank case that isn't coolant I'm sure it will still run forever.
Kettles is offline   Reply With Quote
Unread 03-06-2013, 09:26 PM   #7
aldersonfilm
Registered User
1998 TJ Wrangler 
 
Join Date: Jun 2012
Location: Pasadena, CA
Posts: 177
What about the older systems, like those in the CJ7s, with the locking hubs? Are you actually locking the front differential when you turn them?
aldersonfilm is offline   Reply With Quote
Unread 03-07-2013, 01:11 PM   #8
biffgnar
Web Wheeler
 
biffgnar's Avatar
2006 TJ Wrangler 
 
Join Date: May 2008
Location: Westchester, NY
Posts: 13,320
Quote:
Originally Posted by aldersonfilm View Post
What about the older systems, like those in the CJ7s, with the locking hubs? Are you actually locking the front differential when you turn them?
Nope, you're locking the hubs to the axle shafts. The diff is still open unless otherwise locked.
__________________
Thank you Dave Cole, Dynomax, Falken and all the Spec Class sponsors!!
biffgnar is online now   Reply With Quote
Unread 03-07-2013, 03:23 PM   #9
squirlgod
Registered User
1999 XJ Cherokee 
 
Join Date: Jun 2011
Location: Denver, CO
Posts: 360
THANKS kettles for mentioning the fact that part time has more traction then full time...most people let that slip when they explain this, but its fundamental. More differentials=less traction.
__________________
[B]"Yeah....It's [COLOR="Purple"]Purple[/COLOR]."[/B]
squirlgod is offline   Reply With Quote
Unread 03-07-2013, 04:42 PM   #10
aldersonfilm
Registered User
1998 TJ Wrangler 
 
Join Date: Jun 2012
Location: Pasadena, CA
Posts: 177
Why didn't Jeep put locking diffs as stock? Land rovers had 'em.
aldersonfilm is offline   Reply With Quote
Unread 03-07-2013, 04:58 PM   #11
biffgnar
Web Wheeler
 
biffgnar's Avatar
2006 TJ Wrangler 
 
Join Date: May 2008
Location: Westchester, NY
Posts: 13,320
Quote:
Originally Posted by aldersonfilm View Post
Why didn't Jeep put locking diffs as stock? Land rovers had 'em.
They did in Rubicon Wranglers
__________________
Thank you Dave Cole, Dynomax, Falken and all the Spec Class sponsors!!
biffgnar is online now   Reply With Quote
Unread 03-07-2013, 05:21 PM   #12
buildin1XJ
Web Wheeler
1999 XJ Cherokee 
 
Join Date: Oct 2011
Location: Knoxville, Tn.
Posts: 1,568
Your question is very simple Full time means you can run in that gear anytime you feel the need for extra traction. Part Time means when extreme weather or off road conditions exist. 4 Low for more pulling power and extreme conditions only. Never run your XJ in part time unless roads or off road conditions exist.
buildin1XJ is offline   Reply With Quote
Unread 03-07-2013, 05:23 PM   #13
dmill89
Registered User
1995 XJ Cherokee 
 
Join Date: Sep 2012
Location: Harrisburg, PA
Posts: 752
Quote:
Originally Posted by aldersonfilm View Post
Why didn't Jeep put locking diffs as stock? Land rovers had 'em.
A locker and the related hardware to make it work costs allot more than an open diff. See Below.

Quote:
Originally Posted by biffgnar
They did in Rubicon Wranglers
That being said I really wish that the lockers were offered a separate option on Wranglers (and the 4:1 reduction too). I wouldn't mind spending an extra $1,000-$1,500 or so for lockers (I doubt they'd cost Chrysler more than a couple hundred $ but I know there is plenty of mark up) and $500 or so for the lower transfer case ratio, but a Rubicon costs nearly $10,000 more than a base Wrangler sport for allot of options I really don't need/want.
dmill89 is offline   Reply With Quote
Unread 03-07-2013, 05:35 PM   #14
biffgnar
Web Wheeler
 
biffgnar's Avatar
2006 TJ Wrangler 
 
Join Date: May 2008
Location: Westchester, NY
Posts: 13,320
Quote:
Originally Posted by dmill89 View Post
A locker and the related hardware to make it work costs allot more than an open diff. See Below.



That being said I really wish that the lockers were offered a separate option on Wranglers (and the 4:1 reduction too). I wouldn't mind spending an extra $1,000-$1,500 or so for lockers (I doubt they'd cost Chrysler more than a couple hundred $ but I know there is plenty of mark up) and $500 or so for the lower transfer case ratio, but a Rubicon costs nearly $10,000 more than a base Wrangler sport for allot of options I really don't need/want.
Realistically the issue is that DC is running a business and most jeeps never go off road. They are already selling more than they can make as it is.

Along the lines of AWD v. Part Time and lockers, my old Lexus LX470 was AWD but had a locker in the TC (but diffs open).
__________________
Thank you Dave Cole, Dynomax, Falken and all the Spec Class sponsors!!
biffgnar is online now   Reply With Quote
Unread 03-07-2013, 05:43 PM   #15
buildin1XJ
Web Wheeler
1999 XJ Cherokee 
 
Join Date: Oct 2011
Location: Knoxville, Tn.
Posts: 1,568
Well you own a XJ and your only options are to buy lockers of your liking and a Atlas T case can give you more gear reduction. Other than that you can install an electrical system that will keep your rig from shifting into a higher gear when you need to stay in low T case and gear 1 on the transmission.
buildin1XJ is offline   Reply With Quote




Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.