4 Wheel Drive - What is - When to - How To !

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4 Wheel Drive - What is - When to - How To !

Postby jskandhari » Sun Dec 01, 2013 9:37 pm

When I was faced with this question, I did a google up and searched it up, but then I realized why not have it here itself. In a manner which is understandable by all of us, in simple terms.

NOTE: This is not for those who plan to use their SUVs only on Tarmac all the time.

So first of all let us understand the basic difference between various Four wheels drive modes available in market

-> Full-Time 4WD means the vehicle is always making power available to all four wheels, typically shifting the power from the front and rear axles as necessary. Full-time 4WD offers maximum traction under all conditions, and does not require additional input from the driver (to turn on or off). Due to the nature of a full-time 4WD system, you'll find the vehicle does not have the overall on-road mobility of a part time 4X4 package.

-> Part-Time 4WD means the vehicle has a means to select between 4WD and 2WD. It could be a lever or it could a switch. With this setup, you shift between 4WD and 2WD on the go. A vehicle with part-time 4WD provides superior traction on slippery surfaces because the front and rear sets of wheels are (obviously) locked together. It's important to note that vehicles with part-time 4WD systems should not be driven on dry, smooth road surfaces when in 4WD mode. The constant use of 4WD under these conditions can damage drive-train components.

-> All Wheel Drive means the vehicle has an automatic system which will sense which wheel needs how much power and deliver it, the drive doesn't have to flip between modes. This may or may not be to the drivers advantage, on one side the drive doesn't have to get involved much while driving the OBC will determine the condition and will provide the power to the required wheel, however the one looking for true indulgence with the car in terms of SUV performance and delivery as per drivers requirement.

For the ones having Full Time 4WD aka 4x4 & Part Time 4x4 following information would be helpful.

N : Only for when you tow the vehicle behind another ride.
Neutral, the center differential is disconnected from the transmission. So when you tow it, the engine and tranny are inactive. Or if you're not towing, it can roll away on you.

4H : This is your normal mode.
4H means constant four wheel drive, with 53% of the torque going to the rear wheels and 47% to the front(appx). This makes the car behave slightly rear wheel driven (at least unless you have ESP.)

The Center differential is a limited slip in this mode. The front and rear "axle" differentials are engaged. The GV doesn't have axles in that sense because the fully independent suspension requires the use of shorter shafts with constant velocity joints. The front and rear differentials are what's called "open", which means they are simple. These simple differentials are funny. On one hand, they have no ability to allow the different turn rates such as happens during cornering. On the other hand, if a wheel starts spinning, they put all their power into uselessly spinning the wheel lacking traction. This means that on pavement, cornering is impaired, while on slippery surfaces, they allow useless wheelspin. (This is with respect to Grand Vitara, but would also be applicable to other rides)

4H-lock : Actual differential Lock 4 wheel drive.
The centre Differential is lock between the front & the rear axle, both the front & rear axle are moving at same speed.
You shouldn't use this mode on bare dry pavement because you don't need it, and because it will stress the driveline components, cost mileage, and induce unwanted forces into cornering dynamics.
I would suggest NOT using this mode for slippery highway driving. The reason is that when you initiate a turn, even a slight one, a locked center differential will resist wheels turning at different speeds. It wants them all to be turning at the same rate. In a corner, this will cause one or more wheels to slip relative to the road surface. A wheel sliding even a tiny bit has a huge loss of the traction you need for cornering. In combination with the high center of gravity and stiffer suspensions, this is why you see so many SUV's in the ditch on the first slippery corner in sudden winter conditions. In this mode, they are actually worse than 2wd.

4L-lock : Low gear differential Lock 4 wheel drive.
High torque is at your dispense in this mode.

The only difference here is that the center differential has two gears, and this engages the second of them. This gearing halves the speed in any given gear, so you can climb steeper hills, engine brake more slowly downhill, or creep through really rough stuff.
In 4H Lock & 4L Lock modes, the center differential is locked which means the rear and front axles are spinning at the same speed. The front and rear axle differentials are still not locked, i.e with one side spinning all torque goes to the other side (unless you have ESP which brakes the spinning wheel.) A non-ESP car will get stuck if, say, the front right and rear left tires loose contact, even if you're in center Lock mode.

Four Wheeling Tips

1. Most systems can be shifted into 4-Low as the vehicle is moving forward very slowly at 1-2 mph with the transmission in neutral. Alternatively, you can stop the vehicle completely and engage 4-Low. Wait for the drive system lamp to stop flashing before shifting the transmission into gear.

2. To shift back from 4-Low to 4-High, slow to 1-2 mph with the transmission in Neutral. Wait for the drive system lamp to stop flashing before shifting the transmission into gear.

3. Always engage 4-Low before you need it, and if you're in doubt about the conditions, slow down and select 4-Low.

4. Never operate 4WD on hard dry surfaces.

5. If the vehicle has an "Auto" setting, it will prove ideal for use when road surfaces vary (for example, wet or dry, snowy or dry, etc.). Typically, driving in this mode results in slightly lower fuel economy than the 2WD mode.

6. Even with 4WD, slow and steady is much more important than fast and aggressive.

7. When in 4WD, the front wheels will feel as if they are "pushing" or "skidding" in a tight turn. Don't worry! This is normal.

8. Treat loose or wet surfaces as if they are ice. That means you should do everything (brake, accelerate, turn) slowly and gently. This approach keeps the tires from spinning on acceleration and it also keeps them from locking up on deceleration.

9. If you have driven through deep water or mud or deep wet snow, apply your brakes several times at low speed to dry them out. Keep in mind that water, mud and deep snow will affect brake operation.


Before you all start thinking I have written it no, I have simply complied it from the following sources and people at the said sources need to be given due credit for this:-
Suzuki Forums : N-4H-4HL-4LL
Mobioil: Four Wheel Drive How-to
J-asneet S-ingh K-andhari
Ride Safe - Follow Rules - Relish Driving - Have Fun but not at the Cost of Others
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