4WD Auto vs 4WD Lock comes down to who decides when the front axle pulls. In 4WD AUTO the truck drives the rear wheels and brings in four wheel drive on its own when it senses slip; in 4WD LOCK the front and rear turn together the whole time, a setting meant for snow and ice rather than bare pavement. The transfer case pages of your own owner's manual say exactly which surfaces each one is for. So Auto is for a road that keeps changing, and Lock is for a road that is slippery from end to end. If you are shopping for a truck with the five position dial, browse our new Ram 1500 inventory and ask our team which transfer case a given truck carries.
The manuals quoted here are the 2025 Ram 1500 owner's manual, for the half ton, and the 2022 Ram 2500 and 3500 owner's manual, for the heavy duty side. On a Ram 1500 whose dial shows 4WD AUTO and 4WD LOCK, the transfer case pages of that truck's own owner's manual are the final word; Mopar's owner information site carries the 2026 Ram 1500 owner's handbook.
If you came here about the low range, our guide to when to use 4 High vs 4 Low answers that one.
Key Takeaways
- 4WD AUTO decides for you. On a dial that has it, Auto is the on demand setting: it drives the rear wheels and brings in the front axle when the truck senses slip. Your owner's manual says exactly how yours works.
- 4WD LOCK holds the front and rear together. It does not wait for slip, which is what you want on a road slippery from end to end.
- Dry pavement is the dividing line. Your owner's manual says whether Auto may stay on over dry pavement. The 2022 Ram 2500 and 3500 owner's manual says driving its locked positions on dry hard surfaced roads "may cause increased tire wear and damage to the driveline components."
- The 2022 heavy duty transfer case pages show no Auto position. The 2022 Ram 2500 and 3500 owner's manual lists 2WD, 4WD HIGH, 4WD LOW and N on its electronic cases, with the same dry road warning.
- Which trucks have Auto is a sticker question. Read the window sticker or ask our team.
- Neither setting stops you any sooner. Slow down for ice in either one.
What 4WD AUTO Does
On a Ram whose dial has it, 4WD AUTO is the on demand setting. On bare pavement the truck drives like two wheel drive. When a rear tire starts to spin, the transfer case brings the front axle in without you touching the dial.
The 2025 Ram 1500 owner's manual says 4WD AUTO "sends power to the front wheels automatically when the vehicle senses a loss of traction" and "may be used during varying road conditions," and its dry road warning is written for 4WD HIGH and 4WD LOW. That makes Auto the setting you can leave on while the road changes under you. For another model year, the transfer case pages of that truck's own manual have the last word.
What 4WD LOCK Does
On a dial that has it, 4WD LOCK is the setting that holds the front and rear together so they turn at the same speed. The 2025 Ram 1500 owner's manual lists that locked high range as 4WD HIGH and says it is for "loose or slippery road surfaces only," so if your manual's position list shows 4WD HIGH rather than 4WD LOCK, that is the paragraph to read.
Lock does not wait for slip. On packed snow that is the advantage, because the front axle is already pulling before a rear tire breaks loose. On dry pavement it becomes the problem. In a turn the front wheels travel a longer path than the rears, and with the two forced to the same speed, the tires and the driveline take the difference. The 2022 Ram 2500 and 3500 owner's manual puts it plainly for its locked positions: "Driving in the 4WD HIGH and 4WD LOW positions on dry hard surfaced roads may cause increased tire wear and damage to the driveline components." Your own owner's manual says how that applies to Lock on your truck.
The Heavy Duty Dial on the 2022 Pages
The 2022 Ram 2500 and 3500 owner's manual describes two electronically shifted transfer cases, one for the six speed and one for the eight speed transmission, and a manually shifted case, each marked "If Equipped". The electronic pages list 2WD, 4WD HIGH, 4WD LOW and N, and the manual lever reads 2H, 4H, N and 4L. None of those 2022 pages lists an Auto position.
In that 2022 manual, 2WD "is for normal street and highway driving on dry, hard surfaced roads," and 4WD HIGH "allows front and rear wheels to spin at the same speed." It carries the same warning about tire wear and driveline damage on dry hard surfaced roads, and it limits 4WD LOW to 40 km/h.
So on a 2022 Ram 2500 or 3500, bare pavement means 2WD and a road slippery from end to end means 4WD HIGH. For a newer heavy duty in our new Ram 2500 inventory, read the window sticker and that truck's own manual, or ask our team.
Prairie Cases by Road
The line between Auto and Lock is dry against slippery. Here is where it falls on Manitoba roads, for a truck whose dial has both settings; your owner's manual has the last word on yours.
The Trans-Canada Highway in Freezing Rain
Westbound from Portage toward Brandon in freezing rain, the passing lane can glaze while the wheel tracks stay wet and bare. That is a changing road, and it is Auto's job. Auto can stay on over the bare stretches, where your owner's manual allows it on dry pavement, and it brings the front axle in when a rear tire slips on the glaze. Lock would run over those bare stretches too, which is where locked four wheel drive wears tires and driveline. Neither setting stops you any sooner, so the speed comes down either way.
A Drifted Section Road
A mile road north of Highway 1 after a two day blow, with hard drifts across it and loose snow between, is slippery from end to end. That is Lock's job, with the front axle already pulling when you hit the drift. A drift up to the bumper at a crawl is a low range question, covered in the 4 High vs 4 Low guide above.
A Polished Rink Lot
The lot outside the rink after a game is polished ice with tight turns and a few scraped bare patches. A fully glazed lot is a slippery surface, so Lock suits it. Tight turns across bare asphalt in Lock are where the dry surface warning bites, so on a mixed lot, Auto is the easier choice. If the four wheel drive light flashes instead of engaging on a cold morning, our post on 4WD not engaging on a Ram or Jeep walks through the usual reasons.
The Dry Highway in Spring, Dial Still in Lock
A late storm sends the truck into Lock, and a week later the highway is bare and dry. If the dial never came back, the truck has been running locked on dry pavement; read what the transfer case pages of your owner's manual say about that. Before you leave the yard, check which position the dial and the instrument cluster show. On a dry road, shift out of Lock into 2WD or Auto, following the shifting procedure in your own owner's manual.
Wear, Fuel and Service
On wear, beyond the dry road warning above, the 2022 Ram 2500 and 3500 owner's manual says proper four wheel drive operation "depends on tires of equal size, type and circumference on each wheel." When winter tires go on before the snow stays, put on four that match.
On fuel, the transfer case passages quoted here give no figure for Auto or Lock, so we will not put a number on it.
At Dunn Ram Trucks in Portage la Prairie, our service department does differential, transfer case and 4x4 service. Your owner's manual sets the intervals, and our post on differential and transfer case fluid service explains the work. You can book a transfer case service with our team and tell them how often the truck sees four wheel drive.
Which Rams Have the Auto Setting
The 2022 Ram 2500 and 3500 owner's manual's transfer case pages show no Auto position. Which current trims and transfer cases carry Auto, we will not guess: read the window sticker, or ask our team about the exact truck.
FAQs
What is the difference between 4WD Auto and 4WD Lock?
4WD Auto drives the rear wheels and engages four wheel drive on its own when the truck senses slip, while 4WD Lock holds the front and rear together all the time. The transfer case pages of your own owner's manual say exactly how your truck does it and which surfaces each setting is for.
Can I drive in 4WD Auto on dry pavement?
On a Ram 1500 with the five position case, the 2025 owner's manual says 4WD AUTO "may be used during varying road conditions," and its dry road warning is written for 4WD HIGH and 4WD LOW. For another model year, read the transfer case pages of that truck's own manual before you leave Auto on over bare pavement.
Is it bad to drive in 4WD Lock on dry roads?
Yes, locked four wheel drive and dry pavement do not mix. The 2022 Ram 2500 and 3500 owner's manual says driving in 4WD HIGH and 4WD LOW on dry hard surfaced roads "may cause increased tire wear and damage to the driveline components," and your own manual says how that applies to Lock on your truck. Switch to 2WD, or to 4WD Auto where your manual allows it, once the road is bare.
Should I use 4WD Auto or 4WD Lock in snow?
Use 4WD Auto when snow, ice and bare pavement alternate, and 4WD Lock when the road is snow covered or icy from end to end. Your owner's manual says which surfaces each setting is for on your truck.
Does the Ram 2500 have 4WD Auto?
Not according to the transfer case pages of the 2022 Ram 2500 and 3500 owner's manual, which list 2WD, 4WD HIGH, 4WD LOW and N on the electronically shifted cases and no Auto position. For a newer heavy duty, read the window sticker or ask our team.
The Bottom Line
Use Auto when the road keeps changing, use Lock when it is slippery from end to end, and get out of Lock when the pavement dries. That is the line to start from, and the transfer case pages of your own owner's manual have the last word on yours.
If your current truck has no Auto on the dial and you want one that does, see what your current truck is worth, look through our new Ram 1500 trucks and ask our team which ones carry it, and apply for financing online. Any approval, rate or term is on approved credit.
Tyler Dunn, Dunn Ram Trucks, Portage la Prairie
