Nissan Titan 4wd System Explained (3.0)

[Orange Crush]

NISSAN TITAN 4WD SYSTEM EXPLAINED (3.1)

The 4WD drive system of the Titan is much more than just your typical part time system. The addition of Active Brake Limited Slip (ABLS) and the optional Vehicle Dynamic Control (VDC), Traction Control System (TCS) and Electronic Locking Rear Differential give the Titan much greater capability.

Under good road conditions, you are in 2WD with the rear axle getting all the power. Power is split between the right and left wheels by an open differential. Open differentials are extremely reliable, require very little maintenance and last longer than limited slip differentials. If you have equal traction at both wheels, power is evenly divided between them. If one wheel begins to slip, the open differential begins to send all available power to that one slipping wheel. Normally, this would be very bad.

This is the first opportunity for the Active Brake Limited Slip (ABLS) system to show itself. ABLS applies brakes selectively to the slipping wheel. This braking action literally fools the open differential into sending power to the wheel with traction. When you are in 2WD, this only will send power left to right on the rear drive axle.

Another option when traction is lost in 2WD, is to engage the 4WD system. The 4WD system on the Titan is a shift on the fly system allowing the choice between 2WD, 4HI, and 4LO. It uses a free running hub design that allows engaging and disengaging from 2wd to 4H at speeds of up to 60 M.P.H. This sends exactly half the power to the front axle where another open differential splits power. The center is a locked transfer case (2WD for normal driving conditions or manually selected 4WD) which is why this is a part-time 4WD system). Between the front and rear axle, normally you will be able to gain forward traction but, because of the open differentials, there is a possibility that you wont.

This is when ABLS takes over again. ABLS applies brakes selectively to the slipping wheel(s). This braking action forces the open differential(s) into sending power everywhere except the slipping wheel(s). In essence the ABLS system gives you two “limited slip differentials” – front and rear – to ensure maximum traction, without the costs associated with a true limited slip differential.

Nissan offers an optional locking rear differential that is an electronically activated switch -on-demand locking rear differential that will send an equal amount of power to each rear wheel at all times for extreme off road conditions. However, this is only available when you are in 4LO. Until 2006, Titans with the locking differential did not include VDC/TCS.

The other optional part of this system is the VDC or Vehicle Dynamic Control. VDC will selectively apply brakes and throttle to prevent understeer or oversteer. This is a rather amazing system and does an incredible job of giving the driver control of the vehicle. Understeer is responsible for a large number of rollovers and oversteer is very common on icy surfaces. The Titan will allow you the option to turn off the VDC. The only reason to turn this off is if you are off road and want to be able to spin the tires and/or slide sideways.

However, there is a second part of the Traction Control System (TCS) [bundled with VDC option] that can be hazardous if you are not paying attention. This is the engine speed limiter. This combines the braking action of ABLS with a rev limiter. Your engine speed will be cut back. This allows for controlled forward movement but it will be slow. The danger with this is if it engages when you are trying to pull into fast moving traffic or encounter unexpected loose gravel and slippery surfaces. This danger is minimized when you are in 4WD mode.

Active Brake Limited Slip (ABLS)

When ABS wheel-speed sensors detect a loss of traction in one or more wheels, braking force is applied to that wheel to help slow it down. This redirects power to the wheels with better traction.

Traction Control System (TCS)

The traction control system reduces torque to the drive wheels by altering injector pulse and controlling the Electronic Throttle Control (ETC) motor. If necessary, the brakes are also pulsed via the ABS control unit and hydraulic unit to reduce slipping.

–For injector pulse and ETC functions, the ECM receives wheel slip information from the ABS control unit through the Controller Area Network (CAN) bus.

TCS operates at all speeds and limits drive-wheel slip (wheel spin) under most conditions, improving driver control of the vehicle in slippery conditions as well as on dry surfaces if throttle is over-applied.

Vehicle Dynamic Control (VDC) with TCS and ABS

• The system integrates ABS and TCS with additional cornering controls.

• The VDC control functions (integrated into the ABS control unit) monitor the input from steering wheel angle, vehicle speed, wheel speed, G-force and yaw rate.

• When vehicle stability is affected by road conditions or the need to make an emergency maneuver, the system helps to maintain optimum speed at each wheel.

• The system controls engine output by reducing fuel and throttle opening, and provides individual braking control for each wheel to reduce or prevent skidding.

VDC changes engine power and/or applies the brakes individually as necessary to help stabilize the vehicle in severe turning situations. VDC helps enhance performance in emergency avoidance maneuvers, helps improve vehicle directional stability, and helps provide improved control even on slippery road surfaces.

Note: VDC not available with locking rear differential.

VEHICLE DYNAMIC CONTROL (VDC) SYSTEM (if so equipped)

When accelerating or driving on slippery surfaces, the tires may spin or slide. With the Vehicle Dynamic Control (VDC) system, sensors detect these movements and control the braking and engine output to help improve vehicle stability.

• When the vehicle dynamic control (VDC) system is operating, the slip indicator in the instrument panel blinks.

• When only the traction control system (TCS) portion of the vehicle dynamic control system is operating, the slip indicator will also blink.

• If the slip indicator blinks, the road conditions are slippery. Be sure to adjust your speed and driving to these conditions. See “Slip indicator light”, and “Vehicle dynamic control off indicator light” in the “Instruments and controls” section.

• Indicator light If malfunction occurs in the system, the “SLIP” and “VDC OFF” indicator lights come on in the instrument panel. As long as these warning lights are on, the traction control function is canceled.

The VDC system uses an Active Brake Limited Slip (ABLS) system to improve vehicle traction. The ABLS system works when one of the driving wheels is spinning on a slippery surface. The ABLS system brakes the spinning wheel which distributes the driving power to the other drive wheel. If the vehicle is operated with the vehicle dynamic control system off using the VDC OFF switch, all VDC and TCS functions will be turned off. The ABLS system and ABS will still operate with the VDC system OFF. If the ABLS system is activated, the slip indicator light will blink and you may hear a clunk noise and/or feel a pulsation in the brake pedal. This is normal.

While the VDC system is operating, you may feel a pulsation in the brake pedal and hear a noise or vibration from under the hood. This is normal and indicates that the VDC system is working properly.

The computer has a built in diagnostic feature that tests the system each time you start the engine and move the vehicle forward or in reverse at a slow speed. When the self-test occurs, you may hear a clunk noise and/or feel a pulsation in the brake pedal. This is normal and is not an indication of a malfunction.

WARNING

• The vehicle dynamic control system is designed to help improve driving stability but does not prevent accidents due to abrupt steering operation at high speeds or by careless or dangerous driving techniques. Reduce vehicle speed and be especially careful when driving and cornering on slippery surfaces and always drive carefully.

• If brake related parts such as brake pads, rotors and calipers are not standard equipment or are extremely deteriorated, the vehicle dynamic control system may not operate properly and the vehicle dynamic control off indicator light may come on.

• Do not modify the vehicle’s suspension. If suspension parts such as shock absorbers, struts, springs, stabilizer bars and bushings are not NISSAN approved for your vehicle or are extremely deteriorated the vehicle dynamic control system may not operate properly. This could adversely affect vehicle handling performance, and the vehicle dynamic control off indicator light may come on.

• When driving on extremely inclined surfaces such as higher banked corners, the vehicle dynamic control system may not operate properly and the vehicle dynamic control off indicator light may come on. Do not drive on these types of roads.

• If wheels or tires other than the recommended ones are used, the vehicle dynamic control system may not operate properly and the vehicle dynamic control off indicator light may come on.

• The vehicle dynamic control system is not a substitute for winter tires or tire chains on a snow covered road.

Electronic Stability Control - ESC

Electronic Stability Control (ESC) is a stability enhancement system designed to electronically detect and assist drivers in critical driving situations and under adverse conditions...automatically.

During Understeer:

In an understeer situation, the front end of the car tends to slide out. ESC automatically applies the inside, rear brake to help you acheive your desired turn. It may also reduce the engine's power.

During Oversteer:

In an oversteer situation, the rear end of the car tends to slide out or "fishtail". ESC automatically applies the outside, front brake to help you correct "fishtailing

Advantages of ESC:

• ESC constantly compares the driver's intended course with the vehicle's actual course and compensates for any differences.

• ESC responds to help you drive safely whenever it senses impending wheel lock-up, wheel spin or loss of vehicle control.

• It helps improve traction, maneuverability and stability in all weather conditions.

ESC Assists During All Driving Situations:

• Braking

• Accelerating

• Cornering

Putting Technologies Together to Help You Control Your Vehicle:

• ABS Anti-lock Brake System

• TCS Traction Control System

• AYC Yaw Control Stability System

Traction Control System - TCS

Safe Acceleration and Enhanced Driving Stability.

Among the countless dangers motorists have to contend with are wet, slippery roads where a vehicle can unexpectedly go into a skid. This can happen when accelerating and can make steering or controlling the vehicle nearly impossible. The Traction Control System (TCS) can help in a dangerous situation like this by preventing the wheels from spinning.

The system can also improve vehicle acceleration. Sensors tell the Traction Control System if a wheel is spinning. If this occurs when a vehicle is travelling at low speed, only the spinning wheel is braked. At a higher speed, engine output is throttled until all the wheels regain their grip. A light on the instrument panel indicates that TCS is active.

In addition to contributing to an improvement in driving stability and safe acceleration, TCS also reduces tire abrasion. TCS was initially presented to the public in 1990 and is offered today as a standard feature on many vehicles.

Sources:

-2004 PATHFINDER ARMADA AND TITAN NEW MODEL TRAINING Manual (found on this site)
-2004 TITAN MODEL Introduction Manual (found on this site)
-2004 Titan Price Comparison brochure
-2004 Nissan Titan Owners Manual
-Dealer emails (Fred Schuler Nissan [now Ken Pollack Nissan], Wilkes-Barre, PA)
-Edmunds.com – Toyota forum – Toyota 4WD systems explained
www.conti-online.com
www.contitevesna.com

[FireCapt103]

Nice write up.

[jaho1979]

I only got about 1/4 through it, but very nice write-up, extremely informative.

[cneary812]

so we need to put on big 37's 8" lift kits and never take our foot off the gas pedal???

JK nice job.

[BigA]

Very informative, I don't think the TCS system is that great, its kinda slow to respond and you can only spin one wheel at a time compared to both with a limited slip. But I do think it helps to keep the back end from stepping out around sharp corners which a true limited slip can cause.

[Hot_Titan]

is there a way to turn off the vdc? or is that the same as the burnout mod?

[Aquaholic]

What about 4wd? J/K

[Orange Crush]

Originally Posted by BigA

I don't think the TCS system is that great, its kinda slow to respond and you can only spin one wheel at a time compared to both with a limited slip. But I do think it helps to keep the back end from stepping out around sharp corners which a true limited slip can cause.

I think you mean the ABLS and I agree to a point.

You have to keep in mind that this is a reactive system (unlike a full time 4WD and some AWD systems); it doesn't kick in until slippage or change in yaw is detected, then the system corrects the situation.

As driver/operators we still have a certain responsibility to use common sense in shifting to 4WD as soon as weather/road conditions (and speed) permit to delay the onset of such slippage or change in yaw and/or mitigate its effects. Also we are responsible for the condition of our tires to ensure the maximum possible traction. So we have our part to play in assisting the system in doing its job.

RE: "you can only spin one wheel at a time compared to both with a limited slip". If you spin both wheels you have 0 traction, I don't understand why you think its better?

[BigA]

You have twice the traction, two wheels pushing you up a muddy hill is better then one wheel, twice the contact patch.

[Orange Crush]

Originally Posted by BigA

You have twice the traction, two wheels pushing you up a muddy hill is better then one wheel, twice the contact patch.

Umm, NO. Appearances may be deceiving but per:

http://www.canadiandriver.com/articles/jk/at_010410.htm

By locking one axle to the differential, the other axle is forced to turn.

http://autorepair.about.com/library/.../bldef-254.htm

Limited slip ensures that some torque is always distributed to both wheels, even when one is on very slippery pavement.

http://everything2.com/index.pl?node_id=1126883

Thus, the limited slip differential. The construction is such that even if one of the connected wheels starts to slip, some power from the drive train is applied to the non-slipping wheel.

http://www.houseofthud.com/differentials.htm

As power is applied to the ring gear, and transmitted to the housing, and down into the pressure rings, they start to push on the spider gear shaft which (depending on traction conditions) wedges itself toward the end of the opening between pressure rings, which forces them away from each other, which applies pressure to the clutch packs, which locks both drive gears to the outside housing and under very high power the differential locks up nearly solid.

http://dictionary.laborlawtalk.com/L...p_differential

By limiting the velocity difference between a pair of driven wheels, useful torque can be transmitted as long as there is some friction available on at least one of the wheels.

http://auto.howstuffworks.com/differential.htm

Remember that the open differential always applies the same torque to both wheels, and the maximum amount of torque is limited to the greatest amount that will not make the wheels slip. It doesn't take much torque to make a tire slip on ice. And when the wheel with good traction is only getting the very small amount of torque that can be applied to the wheel with less traction, your car isn't going to move very much.

Clutch-Type Limited Slip

The clutch-type LSD is probably the most common version of the limited slip differential. This type of LSD has all of the same components as an open differential, but it adds a spring pack and a set of clutches. Some of these have a cone clutch that is just like the synchronizers in a manual transmission.

The spring pack pushes the side gears against the clutches, which are attached to the cage. Both side gears spin with the cage when both wheels are moving at the same speed, and the clutches aren't really needed -- the only time the clutches step in is when something happens to make one wheel spin faster than the other, as in a turn. The clutches fight this behavior, wanting both wheels to go the same speed. If one wheel wants to spin faster than the other, it must first overpower the clutch. The stiffness of the springs combined with the friction of the clutch determine how much torque it takes to overpower it.

Getting back to the situation in which one drive wheel is on the ice and the other one has good traction: With this limited slip differential, even though the wheel on the ice is not able to transmit much torque to the ground, the other wheel will still get the torque it needs to move. The torque supplied to the wheel not on the ice is equal to the amount of torque it takes to overpower the clutches. The result is that you can move forward, although still not with the full power of your car.

If you have “two wheels pushing you up a muddy hill” then both wheels are providing traction (and/or spinning at the same rate[with or without traction]) and the ABLS or LSD to will not interfere.

The above links & quotes show quite clearly that the LSD works by limiting the difference in speed (spin/slip) /torque between the wheels on the same axle. Even in situations where only one wheel on an axle has traction, the LSD will still allow the slipping wheel (the one with no traction) to continue to spin (just like ABLS does) in order to be able to transfer torque to the wheel with grip.

ABLS uses the ABS system to create more resistance on the slipping wheel in order to fool the open differential into thinking that the wheel with grip offers less rotational inertia, therefore transferring torque to that wheel. Because ABLS does not (to the best of my knowledge) fully stop the rotation of the slipping tire not all the available torque is transferred to the wheel with grip (just like an LSD). Under snow and ice conditions this is beneficial as too much torque to the tire with grip will cause the loss of traction.

[Justintoxicated]

* Added, Untill 2006, with the exception of some early 04's with offroad package and no locking diff, Titans with the locking Diff do NOT have VDC...

[Orange Crush]

Originally Posted by Justintoxicated

* Added, Untill 2006, with the exception of some early 04's with offroad package and no locking diff, Titans with the locking Diff do NOT have VDC...

Thanks! Amended post to version 3.1