I drive a 2008 Dodge Ram 1500. It has 2wd, 4hi, and 4lo. I have heard from some old timers that if I drive in 4hi at highway speeds it will damage the vehicle. The manual does not say anything about not driving highway speeds in 4hi. I only drive in 4 hi when there is lots of snow on the road (I-25/I-70 between Colorado Springs and the mountains mostly). Does anyone have any good info on this? I understand how 4hi is no good on dry pavement (I’ve made that mistake a few times), but in a snowy situation on the interstate where I am not making any turns, only highway curves, is there anything wrong with it? I am talking speeds like 50-70 mph. Thanks for any info you have, my father and I have the same truck and this will solve some debates.
If it’s a true 4X4 with just a transfer case, it’s not a good idea nor safe to operate it in 4 wheel drive on dry pavement. The reason is there’s no center differential between the front and rear differentails. Just the transfer case. And the transfer case doesn’t allow the front and rear differentials to rotate at different rates while going around corners. This can result in severe wheel hop while cornering and/or damage to the tranfer case because of binding while cornering among other driveline components.
I understand why dry pavement and 4 wheel drive don’t work well together. I am trying to figure out if speed will cause any damage.
Why risk the damage to the transfer case? And why would you need 4 wheel drive on dry pavement?
I drove my 97 jeep grand in 4 wheel hi at reduced speeds around 50 mph a good bit in snow and heavy rain and that was on the same road you drove on, I70 between St Louis and Boulder Co. It had over 240,000 miles on it when I sold it. Transfer case or diffs were on good shape. I was careful to shift out of 4hi as soon as I got out of snow or heavy rain. I have new Wrangler now and will do it the same way.
I don’t believe 50-70 mph will do any harm if there is snow on the road. If the road is just wet, then as far as the transfer case is concerned it is the same as driving on dry pavement. So, if there is snow on the surface of an interstate highway perhaps 70 mph isn’t a good idea.
I have a 4X4 ('01 Toyota Sequoia) and I use 2wd Hi for highway speeds. I only go to 4X4 on dirt roads, snow and icy roads, and driving on sand. Once the snow is off the highway and I feel it is safe to go 60-70 mph I shift from 4wd hi back to 2wd hi. I’d have to pull the owner’s manual but I remember it said driving in 4wd hi on dry pavement would not hurt the Sequoia, but it would reduce gas mileage and could cause more wear on 4X4 components so it wasn’t recommended, or something to that effect.
I only drive in 4 wheel drive when there is snow/ice on the road, much like what Dektol and Uncle Turbo were describing, and I am usually in and out of 4hi depending on the road conditions. The fastest I have ever gone in 4hi is probably around 60 mph on a snow covered road.
As long as you’re driving in snow or other slippery conditions, it probably won’t hurt. Dry pavement could damage it, especially cornering at anything but very slow speeds on dry surfaces. But is there a reason you’d want to go 70 in the snow??
I don’t think it hurts driving in 4x4 mode at highway speeds with snow on it but it may hurt you.
Sure, you can go but stopping is a different story. No four wheel drive on the planet will help you with that.
Just slow down.
“But is there a reason you’d want to go 70 in the snow??”
That’s 20 MPH slower than 90 on dry pavement.
You should NEVER drive a vehicle in part time 4wd at highway speeds, whether it’s dry pavement or slippery conditions. The transfer case with no center differential is locked on these vehicles which makes them totally unforgiving going around any curve as the front and rear drive wheel on each axle is trying to spin at the same rate. On dry pavement it’s hard on the drive train and on snow you can easily loose what traction you have. If the rear wheel looses, you go into a spin.
The only saving grace is that you normally slow down in snow…but, this is a big one, if you have to make a sudden evasive maneuver at highway speeds, you could be in bigger trouble then you ever anticipated. Generally, I use 35 to 40 mph as my upper 4 hi limit. Some newer truck based vehicles with AWD selector switch allows faster snow and dry pavement speeds.
This is why part time systems can be dangerous. If you drive in 2wd with poor weight balance and hit a patch of snow, you can spin as well ! Part time systems are low speed ONLY ! My observation doing accident investigations is that most of the 4wd vehicles I saw off the road in snow were vehicles with part time 4wd that are driven too fast and loose traction while accelerating or turning and start spinning out of control. Inadequate tires exacerbate the situation and make these part time systems MORE of a problem on highways in snow then the quaint little fwd compact.
If you must drive at highway speeds, do it in 2wd ONLY with part time systems exactly like “Uncle Turbo” suggests. ! Newer vehicles with stability control “may” be more forgiving…don’t count on it. Some may actually shut this feature off when in part time 4wd. Mine does.
? I drove a 4wd (not awd) Jeep Cherokee for 12 years in Anchorage. In the winter it was frequently in 4wd high (icy/slippery roads being the rule) and I never had the slightest problem with traction or stability, including driving on the 50-60 mph highways. It had 4 studded winter tires.
To the OP- there’s a reason it’s not specified, because it’s typically not a limitation. I’ve driven 4 wheel drive vehicles most of my life. From my experience, there are no adverse effects on the mechanicals from traveling at highway speeds while in 4 HI. I do it whenever the conditions dictate and have never suffered any type of failure doing so. I’ll leave the arguments on the safety of it to the safety “denizens” of this forum…