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When to and when not to use 4 wheel drive high

edited November -1 in General Discussion
This question comes from this http://www...ay/05.html



So from that is sounds like I shouldn't be using 4 wheel drive on the highway at all or at under some particular speed? What is the highest speed I should be using it in?



I was tought that if it looked icy or if there was snow on the road you put it in 4wdh I once had a Taho that had the auto 4wd which I left it in if the road was ok but sometimes not. However if the road was straight up bad I put it in full time 4wd and I know at times I was in 4wdh at over 50mph



So I guess my question is what is the highest safe speed to be using 4wdh?



Seems to me that most people don't know this because I have never ever been told different than how I learned. Going to be hard to change my ways.



Right now I have 2 pickups a 2008 Chevy Colorado Crew Cab and a 1989 GMC Sierra 1500 both have 4wdh and no option for auto 4wheel drive so I just want to know the best way to drive them safely I live in Northern Minnesota so this is pretty important for me.
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Comments

  • edited January 2009
    anything over 45 50 mph in fwd can mess up your hubs or you gears in the rear end i drive a 97 chevy z 71 and i did the same thing your doing and the machanic that had to go through and rebuild my fwd sestem said that your fwd is if you happen to get stuck not for daily driving the auto fwd is fine if u have it because if your back wheels hang up or get stuck it automaticly inuages the front and when the back starts spinning again the front disenguages
  • edited January 2009
    Theoretically in 4WD Hi you can drive at any speed you want (provided you are not turning), however most of the time conditions will dictate that you not drive very fast, otherwise you wouldn't be using 4WD. For low range due to gear reduction via the transfer case you're going to top out around 30-40 MPH for most vehicles (redline limited). But driving that fast in low range may cause damage to drivetrain.
  • edited January 2009
    If your having trouble getting around you should'nt be going fast enough to do any damage to your FWD!!! I would worry more about stopping and your ABS!
  • edited January 2009
    I would leave the 4WD off unless I was stuck and trying to get unstuck. If the weather is bad enough that you need to drive with the 4WD on, you should be driving slow anyway, so the question is kind of useless. It would be pretty foolish to drive fast in weather in which you felt it was necessary to use 4WD.

    Oh, and no matter what you read here, your owner's manuals have the definitive answers for both vehicles. Read them and let us know that they say.
  • edited January 2009
    "I was tought that if it looked icy or if there was snow on the road you put it in 4wdh I once had a Taho that had the auto 4wd which I left it in if the road was ok but sometimes not. However if the road was straight up bad I put it in full time 4wd and I know at times I was in 4wdh at over 50mph"

    "Whitey" has my vote.
    Not only may if be difficult on your drive train (though it varies from make to make), but it's just plain unsafe with part time 4 wd. That's why many trucks have added auto/awd feature.
    When you lock in your steering wheels, you lock in, not only engine braking, but drive train drag at about 50%. This could cause loss of steering control and is the primary reason so many 4 wd leave the road. Leaving it in 2 wd on the highway at higher speeds will not only encourage caution, but you have a better chance of retaining steerage in a skid. The ability to accelerate to higher speeds in 4 wd is a false sense of security. For safety sake 40 mph or less for me in part time 4 wd. You can "feel" the cornering and braking limits of your truck if your acceleration is limited as well. That extra momentum at speed cannot be overcome by the disadvantages of part time 4 wd.

    By the way, I hope you have plenty of weight in the bed (tube sand). It's more necessary for handling balance than even a 2 wd truck with 4 wd added front differential. Another important neglected factor in safe 4 wd operation.

    Please realize the dramatic difference at speed between a good awd system (not often found in trucks) and part time 4 wd that you have. Part time 4 wd is for low speed. heavy duty use. AWD is all speed light duty. Slip it into 4 wd on hills to maintain speed less than 40 mph, IMO. My 4Runner has an awd feature that I am still reluctant to use above 40 mph like my Subaru or RAV awd.
    The most unsafe vehicle you can drive in slippery conditions I feel. is a part time 4 wd with no weight in the back and poor tires.


    The extra understanding of how and where to use 4wd is not found completely explained in an owner's manual...my hat's off to you for asking questions and doing research before you have an accident.
  • edited January 2009
    Thanks guys I will take a look at the manual in the 89 before I leave for town today and do what it says. I just bought this truck yesterday the 08 colorado is in the body shop was hauling a trailer on sunday and the trailer hit ice behind me went sideways spun us around put us in the ditch and rolled the truck on its side.

    Everyone was ok luckily and I don't know if I was in 4wd or 2wd, the 2 vehicles that were behind me both said the trailer went out behind me and took me with it so I assume it was nothing I did, just a fluke was doing around 50 in a 65 when it happened probably could have been driving slower but was already getting passed every 30 seconds by people doing 70 which tends to excite me a bit more than I would like in those conditions.

    Bought the 89 because I was paying 65 dollars a day plus 30% tax on a rental so figured buying it for 1500 was a bit better deal.
  • edited January 2009
    Were you braking when this happened? Does the trailer have brakes?

    I ask these questions because if the answers to them are "yes" and "no" respectively, that may have been the cause of the wreck. I guess this could happen even if the trailer has brakes, but trailer brakes could help. If the trailer has brakes, they might need adjusted or the trailer might benefit from use of winter tires or tire chains.

    There are two types of trailer brake systems. One is referred to as "surge brakes." With these, the brakes are applied when there is forward pressure on the trailer's tongue. The other system, which I recommend, has electric brakes that are applied by a brake control unit installed inside the truck. These trailer brakes only assist with stopping the trailer, with the truck doing most of the stopping, but the brake control unit can be easily adjusted based on the conditions. If your trailer doesn't have brakes, you might consider getting one that does.
  • edited January 2009
    First off, I would like to address the standard "read the owner's manual" response that comes with the when to use 4wd question. On the two part-time 4wd vehicles I've owned that I had the manuals for, the description of when to use the 4wd or how the system works have been terrible and, in the case of the manual for my Toyota 4x4 pickup, misleadingly worded to imply that you COULD use the 4x4 on dry pavement. I think a lot of it was just translation issues, so maybe the domestic manuals are better.

    Basically, the front and back wheels turn at the same rate when you're actually in 4wd, so the only way you can turn when you're in 4wd is if one or more of the wheels is on something slippery. If you're driving around on dry pavement in 4wd and try to turn, you can cause serious damage to the transfer case and other 4wd components. The more difficult question is considering when to use 4wd on somewhat slippery conditions like a partially snow-covered or icy road. Usually when you go around a bend on a slippery road, all four wheels will slip or chatter a little bit but will generally hold their grip on the road. If it's only partially snow covered, though, there's a chance that one or two of the wheels will start spinning or lock up which can cause you to slide or a skid off the road. The faster you're going the worse this effect will be, so like the others have said, there's no set speed limit for 4hi, but you definitely want to take it slow.

    The auto setting is great for partially snow-covered roads. It uses the same sensors the ABS system uses and when it detects slippage it automatically engages the 4wd. It is a reactive system though, so if you anticipate bad conditions in the next few yards or so it's better to manually engage the 4wd ahead of time, assuming it is safe to do so.
  • edited January 2009
    I recommend 4WD use on snow covered roads at low speeds like 35 MPH or under. I have used 4WD at fifty MPH when driving on roads that were completely iced over with ridges frozen everywhere. It ran well. I don't recommend 4WD use on a highway at 65 MPH, or when there are extensive runs that are only wet. If we knew when we were going to get stuck, we would only use the 4WD then. If conditions are bad on a straight highway, keep it below 55. If conditions are that bad, you should drive slower anyway.
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