Use of 4WD on Slippery Highway

[RUSSELL5000]

I was reading some comments on an RV forum about driving with the truck in 4WD. I was very surprised to see that roughly half of the comments held that driving the truck in 4WD on the highway, even in snow/ice/slippery conditions, would damage the truck. My truck has the manual shift lever for the transfer case, and so I assume I have what the owners’ manual calls the “four-position” transfer case. I note that the owners’ manual states not to operate the truck over 25 mph in 4WD Low, and that the truck is intended to be operated in 2WD on dry, hard-surfaced roads.

I have routinely used 4WD High in snow/ice/slippery conditions. Two weekends ago we were going around 120 miles on the interstate. Some wet snow started up and soon there was a layer of snow on the road. There had been a good snowfall a couple days before and there were patches of ice on the road, which the wet snow now covered. It was quite slippery – the interstate notice signs even came on saying to slow down. We pulled over, shifted into 4WD High, and then continued on at a consistent 45 mph pace. We had no problems, and stayed interested looking at the vehicles in the ditch and the two separate multiple car accidents in the other lane that we passed (it did not appear anyone was seriously injured, as far as we could tell).

I think this use of the truck is as intended and can’t see how anything could be damaged. I am puzzled by the comments regarding damage to the truck through such use that I read on the RV forum; almost half of the comments on a long thread said damage would result to the truck through such use. Am I missing something? If this is the case then why isn’t there some warning in the owners’ manual?



Thanks!

 

[Bob4x4]

As long as the road is covered in snow you are good to go without fear of damage.I've spent hours in 4 hi in many different types of part time 4wd vehicles over snow covered hiways.There is no need to pull over to engage 4 hi,just let off on the skinny pedal and pull the lever.

 

[Jim W]

Russell;
I am on my 6th 4X4 vehicle and I have used the 4wd drive system in all types of terrain from dirt/gravel roads to hard pack surfaces. I have also used the 4X4 system on the highway when the conditions warrant it such as ice and snow covered roads including in the summer months when it has had some very heavy rain coming down on the roads. Under these conditions this will allowing the differential to slip and not bind up where the drive train is bucking. I have always used 4high and not 4 low when driving on the highway keeping the sped under 65 MPH as the fastest, a lot of time no more than 50 MPH. The way I test if I need 4wd is if when turning the front end if it will not slip but instead it starts to lock and un-lock the differential than I do not need the 4wd system. I will shift the 4wd drive system in and out as needed because of the road conditions. The only thing I do is remove my foot from the accelerator, so I have no load on the transmission when engaging the 4wd system.

I have even used the 4wd high when backing up my 5er on a dry surface uphill for a short distance, straight line only. This makes the backing up easier and less strain on the transmission when in two wheel drive only. I have also been known to launch in 4wd high when I am at a stop light. The DW asks is that necessary and I just smile at her as I have just shut down a Corvette or Mustang.

 

[BarryG]

I have driven hundreds of miles at a time (up to 350 miles at a time) in crappy road conditions as well as sometimes when the roads aren't too bad but just patchy with ice or snow pack across the state in 4wd many times here in the winter time. Driving down the highway in 4 wheel drive is not going to hurt your vehicle. I think the real issue is making sharper turns on a hard nonslip surface could cause some issues such as right/left hand 90 deg turn. As Jim put it, it will start bucking or binding up on sharper turns but the gentleness of curves on a typical roadway are not an issue. Once you get on tertiary streets and sharp turns are encountered when tuning from one street onto another or a parking lot then you may/will have issues.

 

[Mingoglia]

As long as you're not regularly binding up, which you can feel in the steering wheel you're golden. Yes, if you drive like this for the vast majority of your trucks life you're going to wear your drivetrain out sooner, but don't be afraid to do it if you're not binding, which as others have said is when you're turning real sharp and you don't have slippage. Even with that, binding every now and then isn't going to do anything and will more prematurely wear your tires than anything. I'd obviously be more careful if your truck is loaded up as this would put even more load on it.

Mike

 

[AH64ID]

As others have stated it's fine, as long as there isn't traction like there is on dry/wet roads.

In 4wd it is very easy to cause binding at the transfer case between the front and rear axles. This is due to the transfer case locking the two driveshafts together. Differences in tire wear, tire pressure, and loading will cause the tires to spin at slightly different rpms and that's when going straight. Throw any corner into the mix, small or sharp, and the tires are all spinning with a bigger difference in rpms. The tires need to have low traction to slip and keep from causing excessive binding.

I too have driven many miles in 4wd but generally if you are above about 25 mph on a flat road 4wd isn't doing any good even if you are on icy/snowy roads. If it's that slick where you NEED 4wd above 25 mph then you probably shouldn't be going that fast. I drive plenty fast on snowy roads, but 4wd doesn't do much so I kick it out. I will then lock it back in for winding sections, slowing, accelerating, etc.

I really wish we had an AWD option for these trucks.

Also, you do not have to pull over to shift into 4wd.

There is a warning in the owners manual telling you that use where not intended (dry, hard surface roads) can cause drive-line damage and premature tire wear. I will go so far as to add that this can even occur on wet roads, especially if you are loaded and the traction is too high for the tires to slip.

 

[KenHwy61]

With such a heavy front, these trucks are terrible for traction in 2wd, especially unloaded. I would not hesitate to switch into 4wd high in any slippery condition at any reasonable speed. As others have said, just make sure the rear wheels aren't actively slipping and spinning faster than the front wheels and relieve the drive line tension by briefly letting off the throttle before moving the lever.

 

[1320Fastback]

You break parts in 4wd in snow or slush there is something wrong with the truck.

 

[RUSSELL5000]

Thanks much.

Icy and slippery roads are the norm around here in the winter. I layer the bed of the truck with tubes of sand from the hardware store; 960 lbs. That helps quite a bit - I notice the rear-end will slide around easily otherwise. I run studded snow tires on all four wheels. I slow down; I have not been in the ditch for thirty years or more. I can live without some excitement!

I have felt the binding on a turn, but am almost always going straight or very slow when turning in 4WD.

What is the difference between all wheel drive and four wheel drive? Is it that the front and rear drive shafts are not locked together?

 

[NIsaacs]

Thanks much.

What is the difference between all wheel drive and four wheel drive? Is it that the front and rear drive shafts are not locked together?

Yes, the transfer case had a differential in it similar to an open differential in your axles. The full time 4x4 was introduced in the early 70's but was not received well, the biggest complaint was fuel mileage. Then the part time kits hit the market only to cause the transfer case to fail because it required the front wheel drive chain to rotate and lube the top shaft and bearings. Left alone it was a good system. When extra traction was needed you could shift the differential into full lock.

When I need 4x4 I use it, wet or dry, high or low, they are not weak sisters. Just watch all the stock/street sled pullers, they will find a weak spot if one exists. It is rare for them to break something.

Nick

 

[AH64ID]

What I would really like to see is a more advanced version of the old full time 4WD setups. The transfer case in my wife's 4Runner would be perfect if it were 250% the size

It offers 2WD, AWD-Hi, AWD-Lo, 4WD-Hi, 4WD-Lo.

Several Jeeps have also offered transfer cases with 2WD, PT, and FT 4WD, which is better than the old setups from the 70's as they offer a 2WD position in the trasfer case.

AWD is just plain better for about 80% of the time I use 4wd, which is generally towing on dirt roads and grades.


Yes sled pullers and drag racers use 4WD which proves that the transfer case is very strong, but that is very different than causing binding. With all the wheel spin of sled pulling there isn't going to be any binding and with drag racing it's a fairly straight line for 1/8-1/4 mile and it's kicked out. IMHO 5 miles of driving with too much traction is worse on the transfer case, but that's just an opinion.

 

[NIsaacs]

Yes, on a sled puller or drag racer the tires are spinning, but that is not because the track is slippery, it's not. It is because of the power applied and the sleds resistance to being pulled. This is what 1000 hp looks like with a super stock chassis, it is actually too much, 700-800 works better. This truck is running a D-60 front and 14 bolt rear, auto and SCS t-case. Every time the truck bounces, the torque spike is huge.



Nick

 

[SSage]

As long as your not binding and bucking harshly your fine. The truck will tell you if it needs to shift back to 2wd very quickly.

 

[AH64ID]

It doesn't matter why the tires are slipping on a sled puller, just that they are slipping. The slipping was my point and makes it a tough comparison for driving on the street. They do put their stuff thru some serious abuse thou!!!

 

[NIsaacs]

Yes they are slipping, but keep in mind what it takes to make them slip. I really think they are getting a bigger/tougher workout than puts-ing around in a parking lot at an idle, hitting a dry patch of blacktop and getting a binding/bucking feel. If that binding is the axle joints from a super sharp turn, then yes, that is hard on stuff. But like I said, I use mine if I need it, they are not failure prone at all.

I just hauled my 7th load of cinders (22K GCW) off a mountain top to make room for a communication tower base and I needed 4x4 for about a 1/4 mile, up empty and down loaded. It is so steep, that in 1st. 4-high, if you get off the brakes, the engine rpm goes to 2500 instantly, so back on the brakes. It is too steep and severe to use the exhaust brake. I need 4x4, lol.

This is part of the base, 34,000 lbs of 1.5" rebar, 30'x30'x3', 60 yards of concrete, (3) 3'x8' pillars that will be at ground level, the rest will all be underground.

Nick

 

[AH64ID]

Yeah they get a workout! But they aren't binding, which is very hard parts and creates far more mechanical failures than overuse does. That's a generalization for all things mechanical.


Why was it too steep for an exhaust brake?

 

[NIsaacs]

Why was it too steep for an exhaust brake?

I tried and it just seemed to severe, it would shut it down instantly, so I just stayed on the brakes till I got off the real steep stuff, after that 2nd would hold with exhaust brake at about 2100 to the level ground. Had fun and now I have 7 loads (49 yards) of cinders at my house My BIL got (2) 6 yard loads so that made up the 60 yards of concrete that will be poured. Unlike me, he would only use 4x4 to go up empty, not loaded on the way down, said it was too hard on stuff:-laf so I guess I am different than most people? Lol.

Nick

 

[TCollier]

My second vehicle was a '79 Cherokee Chief I bought from my aunt. She used it for a horse trailer and other stable /small ranch stuff. It had full time AWD and there was a switch in the glove box to swap to 4WD High. There was no low range. On the highway I got about 11 miles to the gallon. This was not a good vehicle for a teenager struggling to pay rent but man I really liked that truck. I still admire the looks when I see those older Jeep trucks. Anyway, it drove very good and smooth. It was about 14 years old when I had it, can't remember the mileage, i think the odometer had rolled over.
My 06 Dodge did not like dry road 4Low. I did it to to show the buyer it all functioned. I was wincing the whole 2 minutes.