Don’t know if this is still true, but some 4WD systems used to only provide power to one wheel on each axle, depending upon which wheel was slipping. Basically, you had a transfer case that sent power to the front and rear axles, and a differential on each axle. Locking the hubs meant connecting them to the driven part of the axle, but did not lock the differential.
Limited slip differentials used to be quite rare, but I understand that is no longer true. An LSD will power both wheels on an axle all the time, providing true 4 wheel drive,( which is also All Wheel Drive}. Having a solid axle makes it extremely difficult to turn, as the wheels rotate at the same rate. Some mechanism is needed to allow one wheel to turn at a different rate than the other, while still receiving power from the engine.
Part-time 4WD has historically been superior to AWD in really poor traction conditions, and any vehicle so equipped can be used as an ordinary car when the transfer case is manually shifted to 2WD. That said, modern AWD systems typically utilize traction control systems to brake spinning wheels and other tricks which can help maintain control, and are probably as good on paved roads up to the point where authorities close them to travel.
I knew a guy in high school who did that to his Jeep Wrangler. He somehow managed to break the drive shaft (at least that’s how I remember how he described the problem), so he simply removed the driveshaft, put it in 4WD-high, and continued to drive it. In his case it wasn’t so much a roadside fix and more of a case of he couldn’t afford to fix it properly, and this allowed him to continue driving it. He always referred to is as “the front wheel drive Jeep” after that.
Trucks and the like, with 4WD, used to largely have it for the goal of serving as a tractor for a short period of time. You put the vehicle into low gear, turn on 4WD, and start hauling around logs that you’ve cut from a rope behind the truck.
It’s also used for rock crawling and the like… But no major manufacturer puts it in a vehicle for that use.
Possibly, modern 4WD systems have become close enough to AWD to serve as a more general purpose good but I’m not up to date on the topic. I don’t know.
Sure they do. Also, most have ‘Off Road’ packages. Tougher shocks, skid plate or two and a little bit more of an aggressive tire. Tow hook on the front.
My 4Runner Off Road also has the ability to lock the rear differential.
No it does not make it into a rock crawler by any means, but people most definitely use low range for off road use. You’re limited to low speed, but that’s what you want of 4x4 trails anyway.
All of Jeep’s ‘Trail rated’ vehicles are specifically designed for rock crawling. They have to pass the Rubicon Trail, and have features like redesigned front end bodywork to improve approach angles, tow hooks on the front, low range 4WD, etc.
While it’s probably true that most ‘trail rated’ Jeeps never go seriously off-road, they are specifically designed for that purpose. There are a number of vehicles from other manufacturers that are built for the same purpose.
In function, that may be true. In terms of strength and robustness, probably not. A collection of clutches and diffs does not equal the mechanical qualities of a true 4WD system, even if the electronics can sort of make them behave the same way.
AWD isn’t like it used to be. And not all AWD systems are quite alike. Subaru and Audi have been at the AWD game longer than anyone and their systems are among the best. Most other AWD systems are FWD-biased with an added differential and the power is distributed differently in those than in say, a Subaru. Subies also use that “assymmetrical” designation to indicate a lack of odd 90’s and whatnot in the plumbing of the drivetrain so it’s linear from front to back.
4WD used to, and still does mean selectable, and also with a two speed transfer case, a true 4-low setting for extreme downhill/weather/rock crawling.
But modern AWD systems like in the Chevy Blazers and Equinoxes I sell, are selectable AWD systems, either from a button push or as part of a mode selection dial. So that’s a fairly new development. What isn’t is that you still have to drive to the conditions, LOL.
I can’t help noticing that the Wikipedia page for rock crawling (which Sage Rat linked to) features a Hummer H3 in the lead image. That is some masterful trolling!
This speaks to the distinction Sage Rat was making—true rock crawlers are extraordinarily specialized vehicles. A “trail-rated” stock Jeep is not remotely a rock crawler in the enthusiast usage. And the H3 has been the object of much derision from serious off-readers. I used to see “Hummer Rescue Squad” stickers on lifted Jeeps all the time.
I’d bet Sam Stone was using a more casual definition, which doesn’t bother me (FWIW).
The H3 was a joke because the H1 and to a lesser extent, the H2…weren’t jokes. At least, if you’re talking about off-road worthiness. The H3 wasn’t entirely lame, either, just compared to the previous iterations…
Wheeler Lake Trail. About a mile from my house. Not as serious as some rock crawlers, but the first few minutes shows a pretty box stock jeep in some pretty hairy stuff. I’ve done it in an '84 CJ7 that only modification was good BFG Mud Terrain tires.
Rock crawling can have a pretty broad definition, and I see guys trailer highly customized trucks in to do this trail too.
Interestingly it will engage when speeds go below 25mph. I’d say that at those lower speeds it is sort of the same but I would not expect the drive train to be a beefy thus limiting the functionality of that feature. 4WD lock can be very hard on a drive system as any difference in tire rotation either has to be stored as spring energy in the axils, cause the tire to slip, or have something fail. Basically as one moved forward, not only does the drivetrain have to move the SUV but also constantly move it into binding positions.
On my second plow truck now. Not a business. Just for home. 2004 Short bed Dodge. 10,000 lb Warn winch on the back, Western plow on the front. Chained up on all 4 wheels. Hemi under the hood.
I’m about to go plow my driveway, and even with that rig, and having been doing it for 28 years, I have to pay very close attention. If you stick that truck, you are going to have a real, REAL, bad day.
We use 4WD to make it to our remote sites in the winter. Depending on the trail we’ll hold off using 4Lo until we absolutely have to. The reason is that more often than not it just gets you stuck 50 ft further down the trail…
Advise coming from late 70’s early 80’s Colorado. And a former Colorado Ground Search and Rescue team member.
Always go with a friend with another truck. And mount one winch on the back.
Unless you like walking
For our Highschool graduation, three friends and I ‘jeeped’ and camped Colorado in 1979. Two Chevy short bed trucks and a Toy FJ40 with a 327ci that we had dropped into it. Covered nearly 1000 miles… very slowly. Not too much new to us as we where all from Denver.
We always travel with two trucks, 12000 lb winches on the front, 8000 bumper mount back, winter survival gear, and full toolkits and full survival; kits each. We don’t mess around when we’re 70 miles from the nearest road…
