Questions about truck operation in winter, please help

Pretty new to driving myself (including winter driving) so I would be interested to hear the answers to your questions as well.

I can take a crack at number 1: I was told that it is bad for the truck to use the diff-lock at speed, for general use. I use it when I find myself spinning the tires on a bit of ice or whatever. I also understand that it is safe to engage/disengage whilst moving, just not when the tires are actively spinning out...

 

My answers are in Bold /\

Good Luck, and be carefull.





American Trucker

 

GREAT QUESTIONS.....NEW GUY HERE ALSO...interested ,IN READING SOME ANSWERS ON THIS..SOON ..THANKS..

 

Don't use the dif lock while spinning out though. Toggle while moving, or stopped, but you will do some damage if one side is spinning and the other isn't and you hit it.

 

1. The differential locks (different than the power divider lock) should typically only be used when either off-road, or in extremely slippery/low traction conditions on-road. When in use take greater care when cornering as the truck will be slow to respond as the locked differentials will push the truck straight. This can be especially bad on ice. If both diffs are locked and cornering is a problem, you can unlock the rear diff to turn, then re-lock when straight. IIRC, most manuals say to stay below 25-35 mph with the diffs locked. Some newer trucks will automatically disengage the diff locks over a certain speed. As mentioned, NEVER attempt to engage the diff locks while spinning out. You can dis/engage them when moving though, just let off the throttle a bit to assist the movement and then gently back on the throttle to continue.

The power divider (PDL) can generally be used at any speed, just follow the same instructions for dis/engaging as the diff locks, i.e., off the throttle then gently back on. I have driven for weeks at a time at all speeds both on- and off-road with the power divider in. In fact, if I feel it is getting a bit too slippery I will engage the power divider while rolling down the highway (often the reason I can maintain momentum and not have to stop and chain up ). It is recommended that it not be engaged on dry pavement however.

2. For most trucks the default position for traction control is ON, and the switch is to dis-engage it. This allows the wheels to spin which is actually preferred (within reason) under certain conditions such as mud, ice and snow. What you say... spinning is preferable? Yes. I'm not talking about grabbing three gears and bouncing off the rev limiter, I am talking about having the wheels move just slightly faster than the truck is moving. Sometimes when in mud, snow or on ice it is the only way you're going to move. Traction control usually works by either limiting engine power under a slipping condition, by applying the brake on the wheel that is slipping, or both. This can cause the truck to bog down and stop moving forward if TC is on. Normally when driving on-road you will leave the traction control engaged. Some trucks label the TC switch as OFF-ROAD.

3. I'm bad... I use the jake (and cruise) a lot of the time in crappy conditions. A big truck diesel engine generates its maximum torque at low RPMs , eg. maximum torque in my current truck is at 1,200 RPM. That is when you are more likely to break traction.

4. I always chain the front drive (assuming the fifth wheel is more-or-less centred over the drives... which mine always is). It is usually a bit more of a PITA to do because of fenders, but the front drive has slightly better traction than the rear one (in part, that's why the tires on the front drive wear faster). Of course, when chaining you should also engage the PDL and possibly the diff locks if necessary.

5. Just be aware of the ground conditions, go slow and don't lock your brakes. The truck isn't going to suddenly take off on you, but do be aware that it can, and will, slide off steeply sloped or crowned roads/lanes, etc. If it is that slippery and you absolutely need to back there, then put down some sand or other traction aid first. Things to avoid? Other trucks and stationary objects.

 

First off, these are not dumb questions.

Power divider is an air control that "locks" your front and rear differentials together front to rear but not side to side like a posi unit. Look at the front of your rear differential where the short driveshaft goes into it. You will note a separate housing there. That's your power divider unit.

Some "extreme conditions" (logging,etc) have "locking" or "posi" rearends that may or may not have a cab control. These are the units that lock your axles side to side and makes the rearend work like a solid axle.

Traction Control on the newer trucks is an electronic, computer controlled unit with an electric switch on the dash. Works as previously described.

Power dividers can be engaged at any reasonable speed as long as you're going in a straight line, eg if you're approaching a hill you know is slippery. Never on a curve or when you've started spinning.

As to the backup on ice... watch especially close for pedestrians. Foot traffic can't get out of the way as quick as normal and might just slip and fall. Humans suck as traction aids.

 

You likely have both. Power divider is normally a manual lever on the dash (usually on the bottom) right beside the ones for Air Slide 5th Wheel, Suspension Dump, etc. They go left to right and have a steel wire loop or cage over them to prevent accidental engagement.

Best thing I can tell you without seeing the truck is to check with your shop guys. Also have a look through the truck for an Operator's Manual. These typically wind up in a drawer or the bottom of a closet. They give a quite good explination of controls and how to use them.