There's a lot of folks who don't understand their 4WD systems so I'm posting it here. Most of this info is also available on
www.wjjeeps.com but no one seems to read it, so here it is. More detailed information and information on axles available here:
http://www.wjjeeps.com/tcases.htm
Selec-Trac
Primarily found in Laredo, Special Edition, Freedom Edition, and Columbia Edition
Transfer Case: NV242J (I6) or NV242HD (V8)
Transfer Case fluid: ATF+4
Operating Modes
2WD: rear wheel drive only
4 Part Time: locks front and rear axles together, do not use on paved surfaces as it can cause damage to drivetrain components. Off road/snow only!
4 Full time: powers front and rear axles but allows slip between them through use of a center differential. This can be used on any surface or condition
Neutral: allows flat-towing as the transfer case is disengaged from the transmission
4 LO: Locks front and rear axles together just like 4 Part Time, but also adds a 2.72:1 gear reduction, giving you 2.72 times more torque at the wheels but makes your Jeep 2.72 times slower. Not recommended for use above 25mph. Also, not for use on paved surfaces. Off road/snow only!
Editorial Notes: Selec-Trac is the most desired 4wd system for off-road use because of the numerous modes offered by the NV 242 transfer case and the fully-locked 4HI mode. This is desirable for situations where you need lots of wheel speed to keep forward motion, such as snow-wheeling or in deep mud. This transfer case is also quite reliable but occasionally has trouble shifting between modes. Often, a fluid flush helps improve this.
Also, with open differentials front/rear, you have the option of easily installing lockers or limited slip differentials. The Dana 30 and Dana 35 differentials have many options from the aftermarket community, but the Dana 44a only has a few options for lockers.
QuadraTrac-I
Found only on 2004 Laredo I6 models (optional)
Transfer Case: NV147
Transfer Case Fluid: Mopar NV245/247/249 fluid, P/N 05016796AB
Operating Modes
None! The transfer case in this 4WD system is permanently in "4 HI". It uses a gerotor-driven hydraulically operated clutch pack to transfer power from front to rear. It operates just like the more-common NV247 transfer case but does not offer a neutral or low-range selection. This 4WD system will operate as a RWD system until the rear axle slips, at which point the transfer case will send power to the front axle.
Editorial Notes: This 4WD system epitomizes the unfortunate "soccer mom" image that the WJ sometimes carries. Since it offers no low range selection, it is the least desirable 4WD system for off-road use but should still provide good mobility on-road in wet or snowy conditions.
Quadra-Trac II
Found in Laredo and Limited models, standard equipment for V8 models.
Transfer Case: NV247
Transfer Case Fluid: Mopar NV245/247/249 fluid, P/N 05016796AB ONLY
Operating Modes
4 All-Time: Uses a gerotor-driven hydraulically-actuated progressive clutch pack to transfer torque to the front axle. Under normal conditions, the unit operates in RWD but transfers torque to the front axle once wheel spin occurs. Suitable for use on all surfaces/conditions.
Neutral: allows flat-towing as the transfer case is disengaged from the transmission
4 LO: Locks front and rear axles together and disengages the progressive coupler. This also adds a 2.72:1 gear reduction, giving you 2.72 times more torque at the wheels but makes your Jeep 2.72 times slower. Not recommended for use above 25mph. Also, not for use on paved surfaces. Off road/snow only!
Editorial Notes: Quadra-Trac II is a common 4WD system in the WJ and offers "point and shoot" functionality... kind of the "4WD for dummies" system. Not to say it isn't capable, though. With the same 4LO function as Selec-Trac, there are very few situations where Quadra-Trac II will be inadequate.
The NV247 transfer case is generally reliable, but unfortunately does have occasional issues with the progressive coupler used in 4 All-Time. Most service documentation lists ATF+4 as the correct fluid for it, but this is incorrect and Chrysler published a TSB about it. ATF+4 will cause premature wear and binding in the transfer case and will eventually cause destruction of the case. If the coupler fails, then the vehicle will be in RWD mode unless you engage 4 LO.
With open differentials front and rear, the same locker/limited slip options mentioned for Selec-Trac are available.
Quadra-Drive
Special Order for Laredo, Optional for Limited, Standard on Overland
Transfer Case: NV247
Transfer Case Fluid: Mopar NV245/247/249 fluid, P/N 05016796AB ONLY
Operating Modes
4 All-Time: Uses a gerotor-driven hydraulically-actuated progressive clutch pack to transfer torque to the front axle. Under normal conditions, the unit operates in RWD but transfers torque to the front axle once wheel spin occurs. Suitable for use on all surfaces/conditions.
Neutral: allows flat-towing as the transfer case is disengaged from the transmission
4 LO: Locks front and rear axles together and disengages the progressive coupler. This also adds a 2.72:1 gear reduction, giving you 2.72 times more torque at the wheels but makes your Jeep 2.72 times slower. Not recommended for use above 25mph. Also, not for use on paved surfaces. Off road/snow only!
Editorial Notes:Quadra-Drive is the "top-of-the-line" 4WD system offered by Jeep for the WJ. It uses the same transfer case as Quadra-Trac II but added limited slip differentials front and rear called "Vari-Lok". These operate on the same principles as the transfer case, only instead of transferring torque front to rear, they transfer side-to-side. This means you truly have 4 driven wheels with QuadraDrive, something not offered on any of the other 4WD systems. Unfortunately, the same reliability and fluid-compatibility issues from Quadra-Trac II affect Quadra-Drive so transfer case failures are possible.
Off-road, the Vari-Lok differentials give tons of traction and often help the WJ hang with more-built rigs. They function better than most other limited slip differentials because they will lock fully and also operate with one wheel in the air. Unlike the older Trac-Lok differentials offered by Jeep, they operate with virtually no wear and also offer considerably more torque-holding power.
One disadvantage: the VariLok differentials require Mopar friction modifier with their gear oil, making maintenance slightly more expensive. If the wrong amount of friction modifier is added, the differential will either bind or slip too much. Redline's 75W140 gear oil has the proper amount pre-mixed, as does Royal Purple MaxGear. Other oils have *some* friction modifier already added but not enough so you'll have to add a little more until it doesn't bind.
QuadraDrive has one other disadvantage - by adding VariLok differentials, Jeep changed the differential carriers and axle shafts for front and rear differentials. This makes installing any other locker/limited slip impossible without procuring the appropriate parts from a Quadra-Trac 2. If you MUST have a locker, start with a Quadra-Trac II or Selec-Trac vehicle. However, most users of Quadra-Drive are very happy with their operation.
Quadra-Drive II was not available on the WJ. Ever. It was offered on the 2005+ WK Grand Cherokee and is similar to QuadraDrive but added electronic control to the transfer case and differentials...which is either good or bad depending on your point of view. Anyway, when you say your WJ has Quadra-Drive II, you lose all credibility.
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Quadradrive vs quadratrac2
has an 01 limited with the quadradrive and it is pretty freaking great! everything is super automatic and it has front and rear hydraulic lockers from the factory! my icy driveway here in new england is not match for it all winter and u don't have to shift it!
