Nissan Titan 4wd System Explained

[Orange Crush]

NISSAN TITAN 4WD SYSTEM EXPLAINED

The 4WD system is a shift on the fly system allowing the choice between 2WD, 4H, 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.

Nissan is now offering 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 wheel at all times for extreme off road conditions.

During normal driving you have two open differentials working for you (front & rear). 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. Open differentials are extremely reliable and require very little maintenance.

If one wheel begins to slip, the open differentials begin to send all available power to that one wheel. Normally, this would be very bad. This is when the Active Brake Limited Slip (ABLS) traction control system (TCS) takes over. ABLS, applies brakes selectively to a slipping wheel. This braking action literally fools the differentials into sending power everywhere except the slipping wheel.

When you are in 2WD, this only will send power left to right on the rear drive axle.

There is one thing to be careful of in this condition, there is a second part of the TCS 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.

The other 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 slide sideways.

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.

[Gig'em]

Nice post. Where is the source?

[rawze]

great post!!!!!!!!!!!

[jburson250]

Crush, this is excellent! Where'd you find it? Must be a super-secret Nissan file not intended for end users. Thank you!

[PolarisTitan]

awesome post!!

[JerseyDirt]

Originally Posted by Orange Crush

NISSAN TITAN 4WD SYSTEM EXPLAINED


During normal driving you have three open differentials working for you (front, rear and center). Open differentials are extremely reliable and require very little maintenance.

Where is the third open differential? The center differential on the Titan is not open. It is a locked transfer case which is why this is a part-time 4WD system. If the titan had an open center diff then you could keep it in 4WD at all times including on paved roads. What is the source of this information?

[Orange Crush]

Sources:

 2004 PATHFINDER ARMADA AND TITAN NEW MODEL TRAINING Manual (found on this site)
 2004 TITAN MODEL Introduction Manual (found on this site)
 Dealer emails (Fred Schuler Nissan, Wilkes-Barre, PA)
 Edmunds.com – Toyota forum – Toyota 4WD systems explained

[JerseyDirt]

Originally Posted by Orange Crush

Sources:

 2004 PATHFINDER ARMADA AND TITAN NEW MODEL TRAINING Manual (found on this site)
 2004 TITAN MODEL Introduction Manual (found on this site)
 Dealer emails (Fred Schuler Nissan, Wilkes-Barre, PA)
 Edmunds.com – Toyota forum – Toyota 4WD systems explained

What was the source of the info for the center open diff? I would guess the dealer e-mails since they are generally clueless. Your post was great except for that one item which is completely false, I wasn't trying to flame you. I just want to see who is publishing or saying these myths. I hope that its not any Nissan publication.

JD

[Orange Crush]

Originally Posted by JerseyDirt

Where is the third open differential? The center differential on the Titan is not open. It is a locked transfer case which is why this is a part-time 4WD system. If the titan had an open center diff then you could keep it in 4WD at all times including on paved roads. What is the source of this information?

You are correct; there are only open differentials front & rear on the Titan. The center differential is as you describe locked at either 2WD or manually transfered to 4WD.

I will edit to correct. Thanks for catching that!

P.S.: That part came from the Toyota thread, I had concluded that the same was true of the Titan (well at least 2/3 of it ). It was noted that the rev limiter danger was only applicable to 2WD driving situations and I would hazard to guess that the Titan in 4WD the risk of engaging the rev limiter would be greatly minimized.

[IMADOGMAN]

Originally Posted by Orange Crush

Sources:

 2004 PATHFINDER ARMADA AND TITAN NEW MODEL TRAINING Manual (found on this site)
 2004 TITAN MODEL Introduction Manual (found on this site)
 Dealer emails (Fred Schuler Nissan, Wilkes-Barre, PA)
 Edmunds.com – Toyota forum – Toyota 4WD systems explained

Orange, Thanks for the good post...
Where did you find the Training Manual? I went to www.nissan-techinfo.com, but the only Manual I could find was for the Maxima. Your post says it was (found on this site)...????

[JerseyDirt]

Originally Posted by Orange Crush

I will edit to correct. Thanks for catching that!

No problem. Your post was the best and most detailed explanation of these systems and I have a feeling that going forward whenever somene has a question regarding any of these traction devices they will be referred to your post. This is why I thought it was important to point out the one correction that needed to be made.

JD

[mchinna]

Thanks for the post. two questions:

I was not able to disengage from 4WD H to 2WD unless I stopped first and put it in park. Has that been everyone's experience? Could I have been doing something wrong?

The second question relates to over and understeer. I thought oversteer would tend to cause a roll-ever and icy conditions would cause understeer? Since this is my first truck, is there some difference with trucks in this respect?

[JerseyDirt]

Originally Posted by mchinna

Thanks for the post. two questions:

I was not able to disengage from 4WD H to 2WD unless I stopped first and put it in park. Has that been everyone's experience? Could I have been doing something wrong?

The second question relates to over and understeer. I thought oversteer would tend to cause a roll-ever and icy conditions would cause understeer? Since this is my first truck, is there some difference with trucks in this respect?

For your first question: If you were doing this on dry pavement you may have been binding the transfer case making it hard to disengage 4WD. If you are on ice, snow, gravel etc. then you should be able to shift back and forth between 2WD and 4WD while moving.

For your second question: Understeer simply means that the vehicle is not turning as much as the steering input (you turn the wheel and the vehilcle keeps going straight or turns very litttle). Oversteer is the opposite, the back end of the vehicle slides out resulting in more turning (rotation) than the steering input.

Both understeer and oversteer can happen on any road surface depending on which end of the vehicle (front tires or rear tires) loses traction first. This can be a factor of throttle input, suspension set up, sway bars and other factors.

JD

[IMADOGMAN]

Originally Posted by mchinna

Thanks for the post. two questions:

I was not able to disengage from 4WD H to 2WD unless I stopped first and put it in park. Has that been everyone's experience? Could I have been doing something wrong?

The second question relates to over and understeer. I thought oversteer would tend to cause a roll-ever and icy conditions would cause understeer? Since this is my first truck, is there some difference with trucks in this respect?

Answer to your first question...Mine shifts from 4WD to 2WD just fine while moving. You will find that it takes a little time, but it shifts best when there is NO LOAD on the gears (not accelerating or decelerating), although sometimes it seems to help if I accelerate slightly, and then let off the throttle to NO LOAD again...
Give it a try

Oversteer means that the rear end will try to slide toward the outside of the turn, before the front end loses grip
Understeer means that the front end will "push" (not turn), and the rear end will follow without sliding toward the outside of the turn.
Either one could put you in a position of rolling over, depending on the circumstances.

[TheRealJimbo]

Great Post!! My Off Road Package has the ELD (that's my abbreviation for Electronically Locking Differential, no idea what the official abbreviation is ) and I can't wait for snow to try it out . Any chance of getting the post updated with the corrected transfer case info AND appropriatly adjusted for the ELD???