Patriot 4x4 - How does it operate?

All,

On the 4x4 Patriot, I am I correct in saying that the back wheels operate "On demand" when the front wheels slip? Is this why they don't call it AWD (all wheel drive)?

How is it different than all wheel drive, and is it more efficient?

I know there is 50/50 lock mode also, but I am just talking about the normal mode.

Also, the sales man told me that the traction control doesn't really do anything when you have 4x4. Is this correct? I would think it would still help.

-hunter

I found this to be a good read on the subject, although it seems like the lines between 4x4 and AWD are getting blurred by the new drivetrains on the market.

en.wikipedia.org/wiki/All_wheel_drive


Also, traction control is always good. An AWD or 4x4 vehicle can still loose traction.

Salesman all wet...

Yes, 4wd and awd lines are getting blurry. It is done as fuel economy measure. It takes power (read more gas) to turn a transfer case plus the extra weight. New 4x4 tech is turning electronic. I think the jury is still out wether it is truly better or not.

Patriot system uses speed sensors at each wheel and detects slippage based on rotational speed relative to the other 4 wheels. It then channels power to the wheels that are either rotating slower or are not rotating at all.

If I understand the specs correctly a 4x4 Patriot operates as a conventional front wheel drive until slippage is detected. The electronics package then electronically engages the clutch to the rear drivetrain allowing power to flow to the rear wheels. There is also one added feature that most people do not understand. Beyond the application of torque to the rear wheels, the 4x4 system will also manipulate the individual wheel brakes to counteract the differential and also eliminate the need (and more weight) of limited slip differentials. This is also part of their roll mitigation system.

Also keep in mind that the 4x4 lock only works to 10-15mph. Then it will go back to computer controlled mode. Is it like a conventional 4x4 system? No. Is it effective? I would certainly think so and while it probably has it's disadvantages in certain conditions, it probably also has advantages that older systems didn't. Fuel economy and safety come to mind.

There are purists out there who would go back to the days of manual locking hubs if they could and maybe your salesman is one of them, but new isn't automatically bad or useless. I certainly wouldn't recommend the Patriot's system for bog slogging or rock crawling, but based on the specs it certanly is capable of roadless conditions.

T-bar lock

Not sure I understand your question, but I was talking about the little T-bar lock switch. It is only effective under 10-15mph. Above that, the electronic control takes over and manages the system for you.

The 4x4 system itself will kick in automatically at any speed, but the driver has no control over it with the exception of the T-bar, but past 15mph the T-bar switch setting means nothing It's all based on wheel slippage. That's my understanding from the tech specs anyway.

Very good info between the wiki link and MrSensible. Thanks.

I read the same thing for the 0-15mph lock, but there is something that makes no sense to me. The owners manual says that the Lock mode can be activated "On the Fly" and "At any speed".

They don't mention that its only going to be effective only from 0 to 15. I guess I need to research more or ask Jeep.

-hunter

Technically true

I would say that statement is technically true. You can flip the switch any time and at any speed. Does that mean it actually does anything over 15mph? Apparantly not according to the specs.

I think their reasoning is that you can set the switch to on in rough conditions and if you drop down below 15mph it will become active again. That way you don't have to keep toggling it every time you enter or exit a rough patch. Can you imagine the howls from owners if that was the case?

I don't think they are trying to hide anything or obfuscate the issue. Keep in mind Jeep markets this more or less as an "entry level" 4x4 so their target market isn't exactly going to be people of experience with 4x4 technology and design or are they going to be using it in extreme conditions.

If anyone out there is buying a Patriot with delusions of being able to conquer any extreme terrain in their Patriot, I would advise them to maybe reconsider it and look at the Liberty, Wrangler or even a Nitro from what I hear is a Liberty in disguise. I certainly consider it a capable little mule (I wouldn't be buying one if I didn't) that will serve my needs and then some.

This is long, but I think it gives an accurate description of the system...

Jeep(R) Patriot Powertrain and Chassis Offer Best-in-class Off-road Capability, World-class Performance and Class-leading Fuel Economy



* Freedom Drive I 4x4 System Provides Confidence in All Weather Driving
Conditions
* Freedom Drive II Off-road Package With CVT2L Delivers Best-in-class
Off-road Capability
* Second-Generation Continuously Variable Transaxle (CVT2) Gives Customers
Improved Performance and Fuel Economy
* 2.4-Liter World Engine Achieves Class-Leading Fuel Efficiency of 30 Miles
Per Gallon on the Highway

AUBURN HILLS, Mich., Feb. 12 /PRNewswire/ -- The all-new 2007 Jeep(R)
Patriot sets a new standard for off-road capability in the compact sport-
utility (SUV) segment: a fun-to-drive vehicle that delivers best-in-class
Jeep 4x4 capability and class-leading fuel efficiency. The Jeep Patriot,
equipped with its standard 2.4-liter World Engine, achieves 30 miles per
gallon (mpg) on the highway -- fuel-economy numbers not often found on an
SUV.
"Jeep Patriot does for the compact SUV class what the brand icon Jeep
Wrangler does for the extreme off-road SUV class -- it provides the best
off- road capability in its class," said Larry Lyons, Vice President --
Front- wheel-drive Product Team. "Patriot gives first-time Jeep buyers a
fuel- efficient, fun-to-drive SUV with true off-road capability."
WORLD-CLASS POWERTRAIN ENGINEERING
The 2007 Jeep Patriot's powertrain delivers world-class performance,
fuel economy and refinement. Patriot features a standard 2.4-liter World
Engine with dual Variable Valve Timing (VVT), which helps optimize the
torque curve at all speeds. This World Engine produces more power, better
fuel economy and a smoother, quieter ride than engines without dual VVT.
Dual VVT is a technology typically not available on vehicles sold in the
United States in the Patriot's price class. Performance objectives are
targeted to match the best in the segment. The 2.4-liter engine provides
172 horsepower (128 kW) and 165 lb.-ft. (222 N*m) of torque and delivers
class-leading fuel-economy of 26 mpg in the city and 30 on the highway. A
2.0-liter four-cylinder World Engine also is available on front-wheel-drive
Jeep Patriot Sport models and achieves 26 miles per gallon in the city and
30 mpg on the highway.
Jeep Patriot features a standard five-speed manual transaxle and an
available Continuously Variable Transaxle (CVT2). CVT2 is a
second-generation CVT that Chrysler Group engineers calibrated for pleasing
engine response and precise ratio control. CVT2 contributes to a fuel
economy improvement of 6-8 percent compared with a traditional four-speed
automatic transaxle. Patriot also is the first Jeep vehicle to offer a CVT2
with integral low-ratio (CVT2L). The CVT2L's effective first gear in low
ratio is 19:1, which provides the torque necessary for crawling over
moderate rocks and logs and other off- road events.
NEW TECHNOLOGY CREATES JEEP 4X4 CAPABILITY
An electronically controlled coupling (ECC), which is attached to the
Patriot's rear differential, is the heart of Jeep Patriot's Freedom Drive I
and Freedom Drive II Off-road Package four-wheel-drive systems. Patriot's
ECC system is easier to calibrate, more flexible, more precise and lighter
than viscous-coupling or gerotor systems.
The ECC transmits torque to the Patriot's rear wheels through a
two-stage clutch system. An electromagnet powered by current from the
electronic control module operates a low-torque clutch. A cam-and-ball
mechanism amplifies the force of the low-torque clutch, applying the main
clutch that transmits torque to the rear wheels. The control module
calculates vehicle speed, turning radius and wheel slip and transfers
torque based on these conditions. The unit seamlessly interacts with the
Electronic Stability Program (ESP), Anti-lock Brakes (ABS) and Brake
Traction Control systems to ensure torque is transferred as needed,
providing better handling and traction characteristics.
Unlike other on-demand four-wheel-drive systems that rely on pumps or
viscous fluids to transfer torque, the Jeep Patriot's four-wheel-drive
system requires no front-to-rear slippage for activation. Patriot's
state-of-the-art electronic four-wheel-drive system anticipates the need
for added traction and responds to wheel slippage by automatically
transferring power to the rear wheels. The system contributes to Patriot's
excellent fuel economy by operating only when needed, minimizing
power-robbing friction and inertia.
MOST CAPABLE VEHICLE IN ITS CLASS
Jeep Patriot is available in three drivetrain configurations: the
standard front-wheel-drive system, which provides excellent ride and
handling combined with best-in-class fuel efficiency, the Freedom Drive I
4x4 system and the Freedom Drive II Off-road Package.
Freedom Drive I is an available full-time, active four-wheel-drive
system with Lock mode designed to give drivers year-round assurance for the
ability to handle rough weather and low-traction conditions. This active
four-wheel- drive system is recommended for daily use, including slick
conditions that come with rain and light snow. Freedom Drive I features a
lockable center coupling, giving drivers the ability to put the Jeep
Patriot in four-wheel- drive Lock mode to handle deep snow, sand and other
low-traction surfaces.
To activate the Jeep Patriot's Freedom Drive I Lock mode, the driver
pulls up on the chrome T-handle. This lock mode ensures that the ECC sends
the maximum amount of torque to the rear axle (up to 60 percent) for
improved traction.
The Freedom Drive II Off-road Package is an available four-wheel-drive
system that makes the Jeep Patriot a Trail Rated 4x4, creating the most
capable vehicle in the crowded compact SUV class. The Freedom Drive II Off-
road Package includes CVT2L, 17-inch all-terrain OWL tires and aluminum
wheels, a full-size spare tire, skid plates, tow hooks, fog lamps and
manual seat height adjuster.
The Jeep Patriot's Freedom Drive II Off-road Package is available on
both Sport and Limited models. This all-new Jeep technology includes the
CVT2L's best-in-class 19:1 low ratio, which is ideal for crawling over
obstacles. Off- road Brake Traction Control maintains forward movement
during heavy articulation or on split-friction surfaces where one wheel
loses traction. Hill-descent Control modulates brake hydraulic pressure
without driver intervention, providing downhill assistance at a safe and
controlled rate of speed. Brake lock differentials improve the Patriot's
mobility by applying brake force to the driven wheel that is spinning
faster than the mate on the same axle. This provides an equal amount of
torque for each wheel, thereby providing torque to the wheel with the most
traction. This helps when crawling over obstacles, during heavy
articulation activity, or when the driver encounters split-friction
surfaces or off-road driving conditions.
Trail Rated Jeep Patriot models also include a heavy-duty cooling
module, a full-size spare tire, skid plates (that protect critical
components like the engine, transaxle or fuel tank during off-road
driving), and tow hooks designed to get even the best off-roaders out of a
tight spot. Standard three- mode ESP and off-road ABS also add to the
Patriot's inherent off-road capability.
Drivers can select four-wheel Lock mode on Jeep Patriots with the
Freedom Drive I and the Freedom Drive II Off-road Package by pulling up
once on the T- shaped off-road handle in the center console. Once the
off-road handle is pulled, an amber "off-road" message in the cluster
lights up to confirm the system is on.
The Patriot responds rapidly to aggressive throttle input and delivers
better traction performance for off-road maneuvers than in the normal mode.
At speeds less than 10 mph, the maximum amount of torque is sent to the
rear axle, which effectively locks the front and rear axles together at a
50/50 torque split for optimum traction performance. At speeds less than 25
mph, the calibration for the ECC is more aggressive. At speeds above 25
mph, the coupling delivers the same amount of torque to the rear axle as in
the normal mode.
When in Off-road Mode with the 4WD Lock engaged and the shifter in the
"L" or low ratio position, the following conditions are engaged
automatically for optimal capability and performance on Jeep Patriot Trail
Rated models equipped with the Freedom Drive II Off-road Package:
* CVT2L provides an overall first gear ratio of 19:1 for crawling over
large obstacles until the vehicle approaches a speed of 10 mph or more,
when it ratios up to maintain speed

* Engine/throttle calibration is optimized for off-road driving

* Off-road ABS calibration is activated (as on non-Trail Rated vehicles)

* Traction Control reverts to brake lock differentials to help maintain
forward mobility during heavy articulation or on split-friction surfaces
when one wheel loses traction

* Hill-descent Control, a first for Jeep, modulates the brake hydraulic
pressure without driver intervention to provide downhill assistance at a
safe and controlled rate of speed. This feature uses grade-sensing logic
to determine if the vehicle is descending a hill or traveling on level
ground

* A green icon showing a vehicle descending a hill appears in the cluster
when the Off-road Mode is activated and CVT2L is in Low or Reverse

ACHIEVING TRAIL RATED STATUS
Jeep Patriot Trail Rated models are designed and tested to perform in a
variety of off-road conditions defined by five key consumer-oriented
performance categories. These include traction, ground clearance,
articulation, maneuverability and water fording, as well as measurements
that demonstrate the engine and transmission continue to self-lubricate,
while the vehicle is traveling up a side slope or on a fore/aft grade, for
consistent performance and capability. The testing for these performance
criteria is performed through a combination of physical testing and virtual
modeling.
The Trail Rated Jeep Patriot sits 1 inch higher than non-Trail Rated
versions and meets Jeep off-road capability requirements for traction,
water fording, articulation, maneuverability and ground clearance. Jeep
Patriot features standard 16-inch styled steel wheels and all-season tires.
Available 17-inch wheels and OWL tires contribute to the Trail Rated
Patriot's 9 inches of ground clearance, 29.6-degree approach angle,
34.2-degree departure angle and 23.3-degree breakover angle. Trail Rated
Jeep Patriot models also have additional body sealing and high-mounted
drivetrain vents to support 19-inch water fording capability. The Jeep
Patriot's body and chassis were developed and tested over numerous rugged
off-road terrains to meet the requirements of the enthusiast Jeep customer.
The Trail Rated badge communicates to the customer that Jeep Patriot 4x4
with the Freedom Drive II Off-road Package delivers authentic 4x4
capability.

The question becomes how long, and how much slippage will occur prior to the rear wheels kicking in at speeds greater than 10-15 mph? I have a habit of heading to the hills on snowy mornings before the plow dudes get to work. In the old Cherokee one could just lock it in 4-hi and ignore (almost) a foot or so of slush - or at least drive comfortably at 30-40 mph. I'm hoping the Riot will do the same - the front drive will be an improvement over the cherokee, (not to mention considerably improving the cost of gas for a ski day), but if the 4x4 system suddenly jerks the rear end in, I will be disappointed... (pray for snow!)

From what I have been reading here, it sounds like the T-lock has possibly desireable use for those who need an additional *off the line* traction/power boost. If you engage the T Lock while stopped (at a stop light for example) and then put the hammer down as they say, a traction/power boost could be realized up to 15 mph. The off the line acceleration wouldn't care about the hill descent or stability features being on I would think. Once past the 15 mph mark, it sounds like it is all systems normal.

Just my .02

knobber said:

When going down a steep, rocky jeep trail with off-road and 4x4 engaged there is a grabbing sound that keeps the speed at 5 or less. Is this sound normal? It is very worrysome. Knobber

Click to expand...

That's the HDC at work. Think of it as the sound of technology.

About the 4wd vs. AWD question, 4wd is when the center diff is locked (4wd lock mode on the pat - under 15mph) and AWD is when the center diff is open. Anything else like the Patriot in normal mode (two wheels spinning and transfers torque in demand) is considered AWD. True 4wd has a locking center diff.

This blurrs the line even more

I know what you are saying about the diff lock in conventional 4wd, but the patriot system has an electronic answer to that as well in the fact that the system can manipulate individual wheel brakes to counteract the conventional diff. Is it as heavyduty as a traditional diff lock in the xfer case? No. Does it do the trick 90% of the time? Probably.

That's really not a new trick. They just took a page from farm and earthmover equipment which has used dual, manual brake pedals for almost 100 years. Their just putting and electronc spin on it (pardon the pun).

To answer another question. Since everything is electronic the response time to slippage is probably measured in milliseconds. However you are engaging mechanical devices using electronics so a good guess would average under a second. In questionable conditions (conflicting sensor reads) maybe up to 2 seconds max. I'd have to looks at more detailed specs to eliminate that caveat. I doubt CRX has that info available because that would certainly be a trade secret.