Many EVs Aren’t Legal on Park Service 4WD Roads
Many EVs Aren’t Legal on Park Service 4WD Roads
Sign up for daily news updates from CleanTechnica on email. Or follow us on Google News! A recent story at Jalopnik tells us the story of a Subaru driver who got in trouble for going on the wrong trail. Why? Because the National Park Service only allows four-wheel-drive vehicles on ... [continued]
Almost nothing in this article is accurate. AWD vs 4WD has nothing to do with locking front and rear differentials. It is that one has a transfer case, and the other does not. Most 4WD vehicles have open front and rear differentials.
The National Park Service doesn’t require locking differentials, so I’m not sure where this person got that idea from. They do however require that they have a transfer case, which the Cybertruck and Rivian do not. So despite the author claiming those would be 4WD, they are not. And do not qualify by the definition used by the NPS.
I think they are correct that there may be a need to update the rules since EVs have no need for a transfer case since there is no mechanical connection between the front and rear axles typically. It’s terrible to try and make that argument with all of your other information incorrect however.
Thank you for this, I was part way through and questioning my sanity.
Though now I'm thoroughly confused as to where my Audi Q7 Quattro stands in the grand scheme of things...
Apparently AWD:
Generally if there is a question of AWD vs 4WD, the only thing you need to look for as an ability to shift to 4 low. It changes the final drive ratio so all of your gearing is dramatically lower. It’s a capability that requires having a transfer case. Though I’m sure there are some weird exceptions out there of 4WD vehicles that don’t have 4 low, it’s a pretty simple rule of thumb to decide which side a vehicle falls on.
It’s possible to have an AWD vehicle that has a clutch or some other way to disengage two of the drive wheels. So you can have a selectable RWD or AWD. This is different than how a transfer case works though, and does not allow a change in final drive ratio.
What's a transfer case and how does it help you go on bad roads?
In a conventional two wheel drive vehicle, the driveshaft goes from the transmission in the front to the differential in the rear. In a four wheel drive vehicle, a transfer case is mounted behind the transmission instead. This splits the power between two driveshafts, one going to the rear differential and one going to the front differential. This gives power to all four wheels, allowing the vehicle to traverse roads where the traction might rapidly change and differ between the wheels.
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That’s not true though. There are plenty of AWD vehicles that can swap between driving all of driving two. And there are plenty of examples of 4wd vehicles that drive all 4 full time. The humvee is a perfect example of a full time 4wd. It cannot switch to 2wd unless you remove a driveline. What it does have is a 2 speed transfer case that allows switching from 4 hi to 4 lo.
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