4WD Low vs 4WD High | What is the Difference? **Heavy Duty Mechanic Explains**

as you guys can see we are in four wheel drive high that wheel and that wheel are spinning this wheel is spinning [Music] what is going on today guys my name is alex welcome back to the channel today we are talking about four-wheel drive low what it is how to use it when to use it and some common myths with four-wheel drive low my favorite so stay tuned for that so if you guys are following the channel you know i've talked about four wheel drive low here and there in the past but i figured i would dedicate a single video going over exactly what four wheel drive low is and uh well this is my 2022 ram 2500 power wagon beautiful truck and it is a perfect truck for all of these demonstrations because it has basically every off-road component you could want on a truck so most trucks come with four-wheel drive high and four wheel drive low four wheel drive high is using the same gear ratio as two wheel drive and simply splitting the power 50 50 in the transfer case driving your front drive shaft i figured most of you guys know that four wheel drive high is used for well driving at higher speeds like on a snow covered road when you're going above 30 40 kilometers an hour so this is your transfer case right here and this transfer case has two functions first function is going from two wheel drive to four wheel drive and the second function is going from high range to low range now that gives us a total of four options so two wheel drive high two wheel drive low four wheel drive high and four wheel drive low now most trucks if not all trucks don't have the option of two wheel drive low however that is 100 possible with basically any transfer case and most manufacturers just don't give you that option because well i feel like they just think it's not really that useful and two-wheel drive low i don't think it would get much use anyways however it is a possibility now we know the transfer case splits the power of 50 50 from front and rear in four-wheel drive we also know what it's like driving at high range you do it probably 95 of the time so that leaves us with low range what the hell is going on with the low range in the transfer case so going into low range in the transfer case simply just changes the final drive ratio of the vehicle so for example this transfer case in this power wagon has a low range of 2.6 to 1 meaning if in high range the final drive ratio in first gear let's say is around 20 to 1. if we go into low range and either two-wheel drive low or four-wheel drive low most likely the final drive ratio will now become 50 to one now the final drive ratio of vehicle basically just means how many times the wheel is spinning in comparison to the engine or the crankshaft so if you have a final drive ratio of one to one which most vehicles do usually when you're traveling around highway speeds what that means is for every one wheel rotation the engine or the crankshaft is also rotating one time hence one to one now doing the math a 50 to 1 final drive ratio means that this tire is turning once while the crankshaft is turning 50 times in that one tire rotation now a higher final drive ratio is great for one reason because it delivers more torque so torque and wheel speed are proportional to one another so like i said with this power wagon our transfer case is 2.6 to 1 that's the ratio between high range and low range so if we were to put it in low range this wheel would spin 2.6 times slower however we would have an increase at this wheel of 2.6 times the torque so in a very simplistic way that is what low range does it simply just increases the final drive ratio of a vehicle we can also think of low range as simply just a gear change so going from let's say third gear to first gear is essentially doing the same thing as going from four wheel drive high to four wheel drive low you're just changing the final gear ratio and bumping up your torque as well as lowering wheel speed so a perfect example is my bike here so as we can see the wheel is turning quite fast in comparison to the crank here um and well at first it was pretty difficult to get it going so if we stop the wheel now we've dropped the gearing here and for our example we'll call this low range for the bike and as you guys can see it's a lot easier to turn the pedals and the wheel turns a lot slower in comparison to the crank this is because this gearing produces a lot more torque and it makes a lot easier to pedal now i use this example with this bike because i think everyone can relate to biking up a hill and when you're in a higher gear you need a lot more torque turn those pedals but what do you do you gear down and therefore allowing you to turn those pedals much easier however you also lose wheel speed hence why torque and wheel speed are proportional to one another so why do people always say four wheel drive low is awesome for off-road well for starters like we've established your wheel speed is dramatically decreased and that allows a lot more control of your wheels in an off-road situation now with less wheel speed comes the increased torque and that is the number one factor why four-wheel drive low is very good for off-road let's say you're going up i don't know a steep grade a bumpy hill torque allows these wheels to just keep on climbing without having to you know put a lot of engine power into these wheels potentially causing them to slip this gives you maximum traction and that is why four-wheel drive low is usually the best option for any off-road situation it also allows you to feel a lot more control of the vehicle it feels a lot more like you're crawling over obstacles versus spinning and you know high revs and in most off-road situations you really don't want any wheel slippage um once a wheel starts to slide the coefficient of friction actually goes down the highest coefficient of friction is a static movement so basically when the wheel is not spinning you have the highest coefficient of friction and that is why you get the most traction with four wheel drive low and in general you really don't want to spin your wheels too much when you're off-road because you know there could be sharp rocks a river crossing last thing you want is to be spinning those wheels on those slippery rocks and losing traction so four wheel drive low is just really good for those types of situations however now that we're on that topic there are some situations where you do want some wheel speed snow is one of those situations because well snow is very slippery so yes four wheel drive low is going to give you some added torque however that torque can't really be delivered on such a slippery surface like snow so the wheels are more likely going to slide in four wheel drive low in theory so in situations like that it may be more beneficial to have that um higher wheel speed and stay in four wheel drive high and just kind of power through the snow a similar argument could be made for sand or mud but once again i think that would depend on the situation in general four-wheel drive low is going to give you the best traction and the best chance and the best off-road experience in most situations all right now the fun part we're going to talk about some four-wheel drive low myths so i do see a few comments every now and again talking about uh four-wheel drive low so i thought i would highlight some myths that i've heard over the years so myth number one all of my wheels lock up when i'm in four-wheel drive low unfortunately that is just not the case like we've mentioned this video four wheel drive low is just a speed range um it has nothing to do with how the drive line actually delivers power to your wheels that happens downstream from the transfer case all the transfer case does is it just splits the engine power 50 50 between the front axle and the rear axle after that it's up to your differentials to decide which wheels get power so if all four wheels don't lock up in four wheel drive high they're also not going to lock up in four wheel drive low and we'll use our beautiful service truck for an example here all right so the rear end is fully off the ground unfortunately there's actually a pause in this truck which who would have guessed so both wheels are going to have to be off the ground this front wheel is off the ground however our front passenger side is on the ground so we'll start in four wheel drive high those three wheels should all spin and in four wheel drive low only those three wheels should spin because the drive line is not going to lock up all four wheels in four wheel drive low we are in four wheel drive let's see what happens so just as i predicted one two [Music] and three wheels are spinning because we have the posi back there but our fourth wheel is just stationary so sorry it's pretty dark here we will shift to four-wheel drive low four-wheel drive low engaged and we will see if we're gonna fall off the jacks here and there we go we have not fallen off the jacks yet now as you guys can see we got one two three and four our fourth wheel is not spinning whatsoever because four wheel drive low does not lock up the drive line completely so as you guys saw not all four wheels lock up in four wheel drive low the same amount of wheels spun in four wheel drive high and four wheel drive low all right myth number two that i hear quite often is that in four wheel drive low my front axle my front differential locks up and again that is just not true i imagine most trucks that people own these days are pretty much all electronically actuated um or activated four-wheel drive systems and when you electronically activate four-wheel drive low that goes to your transfer case there's no wiring connection to your differentials so this is my transfer case and you guys can see the wires going into it so those wires are going to tell the transfer case whether it be in four wheel drive low forward drive high and so on um and that makes sense however if you don't have wires going to your differentials which is a completely mechanical system there's just no magical component that all of a sudden locks it in four-wheel drive low versus four-wheel drive high like we've kind of mentioned earlier in the video um four-wheel drive low stops in the transfer case it has no input what happens down this drive shaft or what happens down this drive shaft and how the power is split between the two wheels that is purely a mechanical differential operation has nothing to do with the transfer case or what range you're in now this truck being a power wagon has the awesome thing of a front differential locker and as you guys can see there is the wire going into the differential to electronically lock it now some trucks will have what's called a center axle disconnect right here and that just simply disconnects the axle from the passenger side wheel it has nothing to do with differential so don't be mistaken when you see wires going to your center axle disconnect coming to my rear differential we have a locker in this differential as well and as you guys can see that is the wire going into the differential to tell it to lock so if we think of power going downstream you start with the engine goes to the transmission comes to your transfer case that's when four wheel drive low is selected and then the power goes down these two drive shafts so if you have an open differential downstream from where four wheel drive low affects the drive line if you have an open differential it's going to stay in open differential and four-wheel drive low so in terms of your front differential locking up in four-wheel drive low that's just simply not the case and unfortunately it's very rare for a truck to come with a front locking differential like i mentioned the power wagon does because well it's just a very off-road focus truck in fact if you have a 3rd gen or 4th gen ram 1500 not a single one of those trucks came from factory with a locking differential wasn't even an option so unless you've installed a front locker yourself or someone else has you're just not going to have a front locking differential unfortunately so i'll do the same thing with my power wagon i'll put the wheels up in the air i'll put it in four-wheel drive low and you'll see that the front differential when it's unlocked never never locks in four wheel drive low so we will put this in four wheel drive high there we go we are in four wheel drive high right now let's put her into drive as you guys can see we are in four wheel drive high that wheel and that wheel are spinning this wheel is spinning however this wheel is not so let's see what happens with four wheel drive low all right so we are in four wheel drive low [Music] so we can see in four wheel drive low once again one two wheel spinning this wheel is spinning but not a big surprise this wheel is not spinning in four wheel drive low so there you go guys four wheel drive low does not lock up the front axle no matter what and i hope that makes sense i hope that shines a light on four-wheel drive low how it works and kind of how to use it it is definitely better off-road maybe that's where some of these myths come into play where uh people think all four wheels lock up just because it is going to give you better traction maybe it feels like all four wheels are locking up because you get better traction however it's just really not the case and there's really nothing that magical about four wheel drive low it's simply just another speed range and at the end of the day all it does is just increase your final drive ratio which slows your wheels and delivers more torque at the same time so i'm going to get to rotating my tires as this truck's pretty much jacked up should be pretty easy but as always if you like the video don't forget to leave that thumbs up and if you like cool stuff like this don't forget to subscribe we'd love to have you guys on board but enough of me we'll see the next freaking video

Channel: The Getty Adventures

Views: 1,136,793

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Id: TlLJYkbPBdA

Length: 14min 37sec (877 seconds)

Published: Fri Jul 01 2022