The 4×4 Guide – Part 1: Basics & Off Road Driving

DSC_0557

Part 1: Basics & Off Road Driving Guide:

Q: Why does “Crow Hop” occur?

A: When a vehicle turns, each wheel rotates on a different radius to the turning circle, thus traveling at different distances and speeds. If the vehicle’s front and rear axles are locked together and are turning on dry surfaces, the difference in wheel speed sometimes results in driveline binding that is released with a bang or vehicle shudder when one of the tires loses traction.

Q: What is 4WD Low Range?

A: 4WD Low Range is a mode specifically designed for temporary use when additional traction and maximum pulling power is desired. Front and rear driveshafts are locked together and engine power is sent through another set of gears to multiply torque. Avoid attempting to engage or disengage Low Range with the vehicle moving faster than 2 to 3 mph (3 to 5 km/h) and do not use this mode for normal driving.

Q: What is the difference between Full-Time 4WD and Part-Time 4WD systems?

A: Full-Time 4WD systems utilize a center differential, which enables the front and rear driveshafts to turn at different speeds, thereby allowing engagement on dry surfaces for normal driving conditions. A Part-Time system does not employ a center differential and locks the front and rear driveshafts together. With a Part-Time system, 2WD mode should be used during normal driving conditions and 4WD mode is to be used only when off-road or on wet or slippery surfaces.

Q: Why can’t you use Part-Time 4WD on dry surfaces?

A: Part-Time 4WD systems effectively lock the front and rear driveshafts together, forming a single driving unit that does not allow for differential action between the front and rear driveshafts. Driveline noise and binding (Crow Hop) may occur when operated excessively on dry surfaces or in turns. This binding can lead to heat buildup and early part failure.

Q: How long can I drive in 4WD High Range?

A: With a Part-Time system, prolonged driving in 4WD High Range is recommended only for wet, loose, or slippery road surfaces. With a Full-Time system, you need not worry about switching to 2WD mode when road surfaces improve.

Q: How fast can I drive in 4WD High Range?

A: You should not go faster than road conditions permit.

Q: Can I shift into 4WD Low Range at any speed?

A: No. With the vehicle rolling at 2 to 3 mph (3 to 5 km/h), shift an automatic transmission to Neutral or depress the clutch pedal on a manual transmission. While the vehicle is coasting at to 3 mph (3 to 5 km/h), shift the transfer case lever firmly through Neutral and into the Low Range position.

Q: Can I shift into 4WD Low Range when stopped?

A: Shifting into or out of 4WD Low Range is possible with the vehicle completely stopped, however, difficulty may occur due to the teeth of the gears not being properly aligned. Several attempts may be required for clutch teeth alignment and shift completion to occur. The preferred method is with the vehicle rolling at 2 to 3 mph (3 to 5 km/h). Avoid attempting to engage or disengage 4 Low Range with the vehicle moving faster than 2 to 3 mph (3 to 5 km/h).

Q: Can I shift into 4WD High Range at any speed?

A: Shifting into 4WD High Range can be made with the vehicle stopped or in motion. If the vehicle is in motion, shifts can be made up to 55 mph (88km/h).

Q: How fast can I drive in 4WD Low Range?

A: Do not exceed 25 mph (40 km/h).

Q: What is Limited-Slip Differential?

A: Provides the same basic functions as an axle differential, but with an added advantage: when the drive wheel begins spinning as a result of being on a slippery surface, a limited-slip differential automatically transfers torque to the opposite wheel to help improve traction.

Q: What is Differential?

A: A gear system that transmits torque to the drive wheels, while also allowing the wheels to rotate at different speeds when cornering. 4WD vehicles have differentials in both the front and rear axles.

Q: What is Jounce/Rebound?

A: The motion of a wheel that compresses its suspension. If a wheel is at full jounce, it is at the upper limits of its travel. The opposite of jounce is rebound — or wheel movement that decompresses a vehicle’s suspension

Q: What is Driveshaft?

A: Shaft connecting the transmission output shaft to the differential drive pinion shaft. Four-wheel-drive vehicles add a second driveshaft from the transfer case to the front differential.

Q: What is Coil Springs?

A: A coil of flexible metal that can be compressed or stretched along its centerline axis without permanent deformation. Coil springs support the weight of the vehicle while allowing the wheels to travel up and down over bumps.

Q: What is Locking Differential?

A: Provides even more traction than a limited-slip differential by “locking” the axle shafts together when the driver wants to do it. Locking differentials do not allow for wheel-speed differences and must not be used on dry, paved roads.

Q: What is Transmission?

A: A mechanism that transfers torque into usable driving power through the use of gearsets. These gearsets multiply engine torque in varying amounts to meet specific driving demands.

Q: What is Breakover Angle?

A: The degree of slope that defines the largest ramp or hill that a vehicle can travel over without scraping against the frame or underbody components.

Q: What is Departure Angle?

A: When returning to level ground from a descent, this angle indicates the degree of a slope from which a vehicle can depart without scraping or hitting the rear undercarriage.

You can check the angle limits in your vehicle service manual

Q: What is Running Ground Clearance?

A: distance from the ground to the lowest point between the axles.

Q: Towing Basics in case of auto transmission 4×4 vehicles.

A: When You Have an Automatic Transmission with Overdrive option.

In hilly areas and with heavy loads, it is recommended you lock the transmission “out” of overdrive to prevent excessive gear shifting
Overdrive can be locked out to promote engine braking on downgrades
Use overdrive with lighter loads and in flat terrain to increase fuel efficiency.

Q: Parking with Trailer Hooked.

A: Avoid parking on grades.
When parking, lock the tow vehicle down with the parking brake, put the tow vehicle automatic transmission in P for Park, with a manual transmission, shift the transmission into reverse and with four-wheel-drive vehicles, make sure the transfer case is not in neutral, and always, block or “chock” the trailer wheels.
Have a guide, whenever possible, have an observer outside of the vehicle and trailer and visible to you at the wheel, especially when backing and parking

Q: Fixed Drawbar.

A: In which the ball platform is permanently welded to the hitch.

Q: Fifth-Wheel Trailer

A: One in which the tongue of the trailer attaches to a specially designed hitch mounted in the bed of a pickup truck. It is most popular with large travel, moving, and horse trailers.

Q: Removable Drawbar

A: In which the ball platform is removable. This hitch is commonly referred to as a utility ball mount.

Q: Axle Ratio

A: On rear-wheel-drive vehicles, rear-axle ratio is an important part of a successful towing equation. It is expressed as a ratio between the driveshaft revolutions per minute and the rear axle’s revolutions per minute. It is always given as a numerical expression like 4.1:1. This means the small pinion gear at the end of the drive shaft must rotate 4.1 times for every single rotation of the rear axle.

Each rear-axle ratio in the spectrum of those offered has a plus and minus. A ratio that is “low” in the number of drive shaft rotations for every axle rotation results in lower engine rpm and in better fuel economy, longer engine life and quieter running. But it won’t be good for quick acceleration, climbing grades, carrying loads or pulling a trailer.

A “high” ratio, one with a high number of drive shaft turns like the 4.1:1 example above, is better for quick acceleration, climbing grades, carrying loads or pulling a trailer. However, it results in lower fuel economy and is noisier when running at high vehicle speeds.

OFF ROAD DRIVING GUIDE:

Once off-road, put your vehicle in 4WD whenever you anticipate a situation that will demand the additional traction. It’s difficult to engage 4WD after you get stuck. You’ll also want to get into the habit of looking over your hood, scanning left to right so you can clearly see what you’re approaching on the trail. If you’re just watching the left tire, there’s a good chance you’ll get the right tire in trouble.

Avoid putting your head outside the vehicle to see what’s coming. Also, many trail masters recommend keeping your thumbs up and out of the way of the steering wheel spokes in rough terrain. For example, if your tire suddenly falls off a rock, your steering wheel could quickly rotate and catch your thumb with a spoke – ouch! Generally, vehicles with power steering, lessen the chance of sudden steering wheel rotation.

Speed and power are not required in rough off-road driving. In low-range 4WD, the low gearing and low speed of a 4×4 vehicles at idle will generally pull you over obstacles. In many cases, with manual transmissions, letting the clutch out slowly and allowing the vehicle to crawl over obstacles in the lowest-gear is the best scenario.

Generally, when snow or mud is present on the driving surface, it is the right time to engage your part-time 4WD system if equipped. If you have an Full-time system like in Defender shift your 4×4 lever to diff lock,

In heavy snow, when pulling a load, or for additional control at slower speeds, shift the transmission to a low gear and shift the transfer case to 4-LO if necessary. Don’t shift to a lower gear than necessary to maintain momentum. Over-revving the engine can spin the wheels and traction will be lost. If you begin to lose traction in snow or mud, turn your steering wheel back and forth rapidly.
This will generally help the wheels bite into fresh terrain and pull you through. If traction is lost, STOP. Wheel spinning will just dig you in deeper.

The key is to maintain forward momentum.
For better traction in sand, drop air pressure 10-12 pounds below normal pressure on conventional tires. (Return to normal pressure after use in these conditions). Try high-range 4WD to maintain forward momentum.
Depending on the condition of the sand, low-range 4WD and alternative gear selections may be necessary. Also try to make wider turns if at all possible. Tight turning slows the vehicle abruptly and can get you stuck. Again, maintaining forward momentum is key.

When climbing hills ALWAYS go straight up or down. It’s also smart to know what’s on the other side before going up. At the base of the hill you should apply more power. Ease up on the power as you approach the top and before going over the crest. If you stall on the ascent, back straight down the hill in reverse. For downhill travel, always use the lowest gear with a manual transmission.

When descending a hill in low-range, do not disengage the clutch and allow the vehicle to coast. Severe damage to your clutch disc may result. Allow the gears and engine compression to slow you down, using the brakes only to fine-tune your speed.
If equipped with an automatic transmission, use low-range and the lowest drive setting. NOTE: NEVER drive a hill at an angle. If the hill is very steep and you don’t feel confident that you or your vehicle can make it up, then don’t attempt it.
call it “crawling” for a reason.
Use a low gear and low-range 4WD and just let the vehicle crawl and idle (with as little throttle as needed) when going over obstacles like rocks or logs. Never straddle rocks. A vehicle with 10 inches of ground clearance will not go over a 12-inch rock! Maneuver the tire on top of the rocks and crawl over them slowly.

Q: Stuck in sand

A: Often because the tyre was not wide enough to spread the load of the vehicle and/or the tread was too aggressive. Sand tyres are advisable for desert crossing.

You’ll probably need a long handled shovel . Jack up the wheels, pile sand underneath them and put Bridging ladders, floor mats, carpet, newspapers or whatever is to hand under the wheels to give the tires some grip. If you have a pump, then reducing the tire pressures by half will help to get traction. Make sure the approach angle to the wheels is gentle. Reduce the weight in the vehicle and drive out SLOWLY.

Dropping tire pressure 3-5 pounds improves traction and helps avoid tire punctures. (Return to normal pressure after use in these conditions). Remember, the ideal speed for rock crawling is 1-3 miles per hour.

Q: Winches?

A: The recreational market has exploded with new winch styles and types.

There are winches made today that are lightweight, electric operated units that make 4-wheeling a little bit easier. And there are still PTO and hydraulic winches available for your rig. But I like using the electric operated winch because if (when) the engine stalls in a bad situation and won’t restart due to mechanical failure (Murphy’s Law), the batteries, if in good shape to begin with, will usually have enough juice left to winch out of the situation. You will then be on better ground to work on the rig!

Tricks:

Leave your ego at home. Every vehicle (and driver, for that matter) has its limitations. Backing off early and accepting that a maneuver is impossible or choosing another approach may prevent vehicle damage and, more important, personal injury. Never try a maneuver that you are uncomfortable with.

Page 1 & 2. Basics, Off Road Driving Guide

Page 3 & 4. 4×4 System By Vehicles

Page 5 & 6. Exhuast Jack /Air Jack, Mud Tires & Mud Driving Technique,Parado DAT System.

Page 7. Fording At Deep Place in Stream,Crossing Water Streams,

Page 8. Tire Pressure, Winch Anchor, CRD Injectors, Word Origin Jeep

Top