Posted by AJ on February 10, 03 at 06:04:22:
In Reply to: looking for advice posted by monica on February 10, 03 at 04:56:53:
Here some suggestions, sort of a "4WD 101":
o '94 Subs have a thermally activated switch that engages 4WD. A known problem is that switch eventually fails, especially at lower outside temperatures. Chevy makes a replacement part that converts it to electronic operation. Its not a free fix, but if you haven't done it yet, 4WD may not engage when you need it.
o Remember that 4WD helps get you going and keeps you moving. It does not mean you can drive as though the road is dry. Lateral forces (cornering) will still cause sliding if not careful.
o 4WD does NEARLY NOTHING for braking. If you're going too fast or following too closely sudden braking will result in longer stopping distance while ABS engages (pulsing pedal) preventing front wheel lockup, while preserving your ability to steer. If you don't leave enough distance, you will likely end up using other objects to finish braking. If ABS does engage, its better to keep your foot on the brake; its unlikely you'll be able to stop any shorter trying anything else. But remember, you can still steer to some degree, which is a major advantage of ABS. Without ABS, once the wheels lockup, you can't steer; you're only along for the ride.
o I believe your Sub should have the floor mounted shifter. It has 3 settings (not including NEUTRAL used for being towed): 2HI (what you normally use most of the time); 4HI (which should satisfy most snow conditions, and can be shifted on the fly); and 4LO (you must be nearly stopped to engage/disengage, can only be used for slow speeds, and should only be used on very sloppy surfaces). DO NOT DRIVE IN 4HI OR 4LO ON DRY PAVEMENT. As wheels speed varies inside/outside around corners, 4WD doesn't allow for variation as well as rear only, and scrubbing tires cause wear to front axles and transaxle. 4HI can be used up to about 45mph or so. If road is slick, I wouldn't advise driving much faster than that anyway. Once you find yourself driving onto a well plowed/dry surface, you can shift back to 2HI while underway.
o A trick I've learned is that many trucks with automatic trans, including Subs, allow you start the vehicle in 2nd gear. This is very helpful when surface is slippery, because torque multiplication is reduced in higher gears, making it more difficult for wheels to spin. Doesn't mean the won't if you gun it, but its harder to spin the wheels starting in 2nd gear versus 1st. On many cars, starting in 2nd means that it will still start in 1st gear, but will only shift to 2nd and no further. No advantage when starting on the slick stuff. In a manual trans, it also works, but you need to slip the clutch and to keep enging from lugging; in an automatic, torque converter takes care of the slippage without any damaging effects. Of course, once you're underway, don't forget to shift back up to DRIVE.
o While in 4WD you will notice some minor additional noise (sort of a low rumble) from the front axle being engaged. That is normal. If you hear loud whining or grinding, or feel significant vibrations, you have other problems and should immediately shift back to 2HI and have the rig checked out. You'll also feel some resistance in the steering during tighter turns, particularly as the road becomes less slippery. This is when you should consider switching back to 2HI.
o Gas mileage will be reduced using 4WD, about 2mpg or so.
o Clear all your windows before leaving, and make sure your head- and tail-lites are visible. Not necessarily easy on a Sub, but clearing snow from the roof is a nice thing to do for the people behind you.
o It would be beneficial to practice turning and stopping in a wide open empty parking lot or such. Once you've gotten a feel for what works, you'll be better equipped to deal with it on the road. Slow down, recognize the need to adjust starting, stopping and turning behaviour/speeds, and you'll be fine. Also, since overalls speed will be less, you should also give yourself more time than normal for your route.
o If you're route is somewhat isolated, I would also highly recommend a "survival" kit, just in case. A cell phone, jumper cables, tools (including necessities for tire changes), blanket, snacks/water, flashlight, and work gloves would be a few good things to have along. Traction pads are also commercially available which might be helpful if you do get stuck.
o Note about tires; stock Sub tires (235-265 widths) should be just fine in most snow conditions. However, significantly wider tires spread out the vehicles weight over a larger "footprint" which lessens its ability to penetrate into the snow. Wider tires have a tendency to "float"; good on sand but not on snow. That's why "muscle" cars are so lousy in the snow, because they usually have very wide tires to provide traction on dry pavement. If you're rig has oversize tires/rims, it may be a good investment to get some narrower tires on steel rims for winter use.
o ICE is different than SNOW. Snow provides some degree of traction, and can be driven with reasonable care. 4WD does almost nothing for ICE. Avoid driving at all if the situation is an ice storm. But if you must, you should have studded tires or chains.
o Once you've settled into driving comfortably in the snow, then you can look out for the others who aren't as well prepared!
Sorry for the long post, but hope at least some it has been helpful.
AJ (remove Z's & X's from email)