Use of part time 4WD advice

[NorthEastRebel]

Hi All,

New to the forum and new owner of a 2019 Ram Rebel, my first full sized truck. As you may know, the only 4WD system available on the Rebel is the part-time system with 2WD, 4WD HI, and 4WD Low. My previous experience has been with SUVs that have full time AWD systems so I've never had to give much thought to using it. I am in the north east with plenty of lousy weather including snow. So AWD has been very useful. I understand that 2WD would be the primary drive mode. But I am concerned with how to appropriately use the part time system on the Rebel, specifically when and how I can use 4WD Hi. The owners documentation describes the process for switching out of 2WD into 4WD and I have done that without problem. It states you can switch to 4WD HI while underway but does not specify any maximum speed at which that can be done OR a maximum speed at which you can operate in 4WD HI. Is there one? I know for LOW you need to be essentially stopped to engage and not exceed 30mph. But there is no mention of any limitations for HI. My dealer was not very knowledgeable and suggested to keep in under 65mph but could not point me to any reference as to why. They also suggested that 4WD should not be operated on dry pavement, but again, could provide no reason or reference.

I ask because it would not be unusual to find myself on the highway with intermittent snow, etc or heavy rain where 4WD would make big difference in traction.

Can anybody fill me in on the appropriate use of 4WD HI or point me to manufacturer reference to recommendations or restrictions?

Thanks in advance.

 

[Brady_SS]

I'm not sure of the speed limit for 4-HI. When you do drive in any 4WD mode it is expected that you will have some wheel slip when turning otherwise the driveline will bind and you could cause damage to it. I've turned mine on a few times to make sure it would engage but only while driving in a straight line. Snow, sand, mud, etc would create the wheel slip expected, not sure wet pavement would.

Edit: I will add that Auto mode, which your Rebel doesn't have is closer to AWD and can be used without wheel slip. That's my choice when it rains heavily and my tires are fairly worn. AWD systems are designed to handle and compensate for the missing wheel slip by adjusting the torque split front to rear and sometimes left to right.

 

[TimG]

With these new shift-on-the-fly transfer cases, you are safe shifting into 4hi at any speed up to around 45mph. If you try to shift it, and you are outside of whatever parameters the computer thinks is safe, it will just flash and stay in 2wd, or give you a notice on the dash that says "action not available/permitted at this time" or something similar. As for top speed in 4hi, that's kind of subjective. I live in a snow covered hell as well (snowed today, actually), and I try to stay below 55-60 when in 4hi in snow. Usually isn't too hard to do because if traction is bad enough for 4wd, its bad enough for me to slow down.
I've never shifted into 4 for just rain. Usually just slow down out here on the prairie because rain like you are talking about usually has hail in it too, and that worries me more than traction lol.

 

[202snowman]

Hi All,

New to the forum and new owner of a 2019 Ram Rebel, my first full sized truck. As you may know, the only 4WD system available on the Rebel is the part-time system with 2WD, 4WD HI, and 4WD Low. My previous experience has been with SUVs that have full time AWD systems so I've never had to give much thought to using it. I am in the north east with plenty of lousy weather including snow. So AWD has been very useful. I understand that 2WD would be the primary drive mode. But I am concerned with how to appropriately use the part time system on the Rebel, specifically when and how I can use 4WD Hi. The owners documentation describes the process for switching out of 2WD into 4WD and I have done that without problem. It states you can switch to 4WD HI while underway but does not specify any maximum speed at which that can be done OR a maximum speed at which you can operate in 4WD HI. Is there one? I know for LOW you need to be essentially stopped to engage and not exceed 30mph. But there is no mention of any limitations for HI. My dealer was not very knowledgeable and suggested to keep in under 65mph but could not point me to any reference as to why. They also suggested that 4WD should not be operated on dry pavement, but again, could provide no reason or reference.

I ask because it would not be unusual to find myself on the highway with intermittent snow, etc or heavy rain where 4WD would make big difference in traction.

Can anybody fill me in on the appropriate use of 4WD HI or point me to manufacturer reference to recommendations or restrictions?

Thanks in advance.

This is from the manual. Take it for what its worth:

This electronically shifted transfer case is designed to be
driven in the two–wheel drive position (2WD) or fourwheel
drive position (4WD AUTO) for normal street and
highway conditions on dry hard surfaced roads). Driving
the vehicle in 2WD will have greater fuel economy benefits
as the front axle is not engaged in 2WD.

For variable driving conditions, the 4WD AUTO mode can
be used. In this mode, the front axle is engaged, but the
vehicle’s power is sent to the rear wheels. Four-wheel drive
will be automatically engaged when the vehicle senses a
loss of traction. Because the front axle is engaged, this
mode will result in lower fuel economy than the 2WD
mode.



The 4WD HIGH and 4WD LOW positions are designed for
loose, slippery road surfaces only. 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.


When operating your vehicle in 4WD LOW, the engine
speed is approximately three times that of the 2WD, 4WD
AUTO or 4WD HIGH positions at a given road speed. Take
care not to overspeed the engine and do not exceed 25 mph
(40 km/h).

 

[Rustydodge]

My previous truck had a similar shift on the fly part time transfer case. When driving down the highway or interstate, if i started to hit ice patches, i'd slightly let off the throttle and flip to 4-hi. always worked perfectly.

When traveling slower offroad and expected i'd need 4-hi, same process. Let off gas and switch to 4-hi.

When going into 4-lo, i always slowed down or stopped, switched from drive into neutral, then selected 4-lo.

 

[NorthEastRebel]

With these new shift-on-the-fly transfer cases, you are safe shifting into 4hi at any speed up to around 45mph. If you try to shift it, and you are outside of whatever parameters the computer thinks is safe, it will just flash and stay in 2wd, or give you a notice on the dash that says "action not available/permitted at this time" or something similar. As for top speed in 4hi, that's kind of subjective. I live in a snow covered hell as well (snowed today, actually), and I try to stay below 55-60 when in 4hi in snow. Usually isn't too hard to do because if traction is bad enough for 4wd, its bad enough for me to slow down.
I've never shifted into 4 for just rain. Usually just slow down out here on the prairie because rain like you are talking about usually has hail in it too, and that worries me more than traction lol.

I will try switching into 4HI at various speeds to see if this is the case. Nowhere in the owner support documentation for my vehicle does it list a maximum speed at which you can switch or at which you can drive once there. For practical purposes I agree that on a snowy road where you need 4WD, I would not normally be going 65+ MPH. But I'd still like to understand the parameters of the system.

 

[NorthEastRebel]

This is from the manual. Take it for what its worth:

This electronically shifted transfer case is designed to be
driven in the two–wheel drive position (2WD) or fourwheel
drive position (4WD AUTO) for normal street and
highway conditions on dry hard surfaced roads). Driving
the vehicle in 2WD will have greater fuel economy benefits
as the front axle is not engaged in 2WD.

For variable driving conditions, the 4WD AUTO mode can
be used. In this mode, the front axle is engaged, but the
vehicle’s power is sent to the rear wheels. Four-wheel drive
will be automatically engaged when the vehicle senses a
loss of traction. Because the front axle is engaged, this
mode will result in lower fuel economy than the 2WD
mode.



The 4WD HIGH and 4WD LOW positions are designed for
loose, slippery road surfaces only. 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.


When operating your vehicle in 4WD LOW, the engine
speed is approximately three times that of the 2WD, 4WD
AUTO or 4WD HIGH positions at a given road speed. Take
care not to overspeed the engine and do not exceed 25 mph
(40 km/h).

Thanks for this. While this info is interesting, this is NOT what is in my owners manual. My truck is equipped with the part-time transfer case and does not have a 4WD Auto mode. In my owners manual the section on 4WD HI makes NO reference to possible damage being caused by driving on dry roads. I imagine it could/would still be true if they work the same way. But supposedly the reason the Rebel only comes with the part time transfer case is that case is more heavy duty? Can't believe manufacturer didn't put clearer info in the owners materials about this.

 

[4sallypat]

This is good to know about the Rebel as I am looking for one.
Same as the OP, I have been used to Auto AWD/4WD so switching between the modes will keep me more alert.

At least it's better than the 1980's where we had to get out of the truck, rotate the center wheel cap to "4WD" on both front tires and then hop back in and engage the 4WD gear.
Then to switch back, hop out and rotate both front caps, hop back in, switch to 2WD, put it in reverse and drive backwards for 50 feet to unlock/unbind the front drive system....

 

[202snowman]

Thanks for this. While this info is interesting, this is NOT what is in my owners manual. My truck is equipped with the part-time transfer case and does not have a 4WD Auto mode. In my owners manual the section on 4WD HI makes NO reference to possible damage being caused by driving on dry roads. I imagine it could/would still be true if they work the same way. But supposedly the reason the Rebel only comes with the part time transfer case is that case is more heavy duty? Can't believe manufacturer didn't put clearer info in the owners materials about this.

Sorry, I forgot rebel didn't have the Auto 4WD, which I belive means its the Borg Warner 48-12 transfer case. Per FCA's media document:

Transfer cases get upgrades Buyers who equip their 2019 Ram 1500 with a four-wheel drive drivetrain can choose between two electronically controlled transfer cases: the BorgWarner 48-12 for part-time 4WD operation with Hi and Low ranges; and the BorgWarner 48-11 for on-demand 4WD. Both transfer cases engage via a push-button control mounted underneath the rotary gear selector on the instrument panel.

The transfer cases are upgraded internally for more robust performance in conjunction with the increased payload and towing capabilities of the new truck. Changes include a larger-diameter main shaft, relocation of the chain and sprocket for improved bearing support, and improved lubrication. Also, the on-demand system is enhanced for quicker response and higher front output torque capacity.

The 48-12 part-time transfer case provides three operating ranges 2Hi (2WD), 4Hi (4WD) and 4Lo (low-range reduction 4WD) plus a neutral position. 2Hi is designed for any road surface at any time, while 4Hi and 4Lo are for offroad use or slick surfaces. The driver can switch between 2Hi and 4Hi while the truck is in motion. To engage 4Lo, the transmission must be in neutral. The low-range reduction ratio (crawl ratio) for 4Lo is 2.64:1, which provides increased low-speed torque capability for pulling power and improved driver control in off-road conditions. The on-demand transfer case has 4Auto, 2Hi, 4Hi and 4Lo selections. 4Auto provides full-time 4WD, responding automatically to provide maximum traction in all road conditions. 2Hi, 4Hi and 4Lo function equally to the part-time transfer case.



http://media.fcanorthamerica.com/pdf.do?id=18758

 

[Hemiguy226]

I’m also new to trucks and I’m disappointed and confused as to why in 4 wheel and turning it hops and feels like damage can be done

 

[Richard320]

I’m also new to trucks and I’m disappointed and confused as to why in 4 wheel and turning it hops and feels like damage can be done

That is the nature of the beast. In 4WD hi or lo, the two driveshafts are locked. There is no differential action. So unless the front and rear axles are turning exactly the same speed, something is going to bind. Then either a wheel hops or you bust a u-joint or a CV joint. In a turn, the two rear tires travel different speeds, hence the need for a differential. The front ones are the same, but the radiuses they turn are tighter than the rear tires. So even with differentials in the axles, the two driveshafts are going to be going different speeds in a turn, But they can't, because they are locked together. If you see a vehicle with All-wheel Drive, they do have differential action in the transfer case.

Back in the 80s and 90s -- and maybe later -- New Process had a full-time transfer case that allowed all the wheels to be engaged on dry pavement, because it had a differential inside. They also had Hi-lock and Lo-lock, which locked the two driveshafts together. The difference? If you parked on ice or mud, it's quite possible that if three tires had traction but the fourth didn't, that one tire would spin and the car would just sit there. Put it in lock and two tires will turn. Have positraction or locking differentials, and you can have three or four turning the same speed, regardless of traction.

 

[devildodge]

The Full time 4wd on Mopar trucks was from 1972 to 1979. 1980 was the first year for part time 4wd and then didnt have a full time 4wd until the 4th Gen. I loved my Powerwagons, Ramchargers and Trailduster with the full time.

Was very nice for Pennsylvania where you get 4 seasons in the same afternoon sometimes.

The only problem with it was if you did get stuck and couldn't get into Hi loc or low loc...you ultimately only had one wheel drive.

Good times.

 

[Hemiguy226]

That is the nature of the beast. In 4WD hi or lo, the two driveshafts are locked. There is no differential action. So unless the front and rear axles are turning exactly the same speed, something is going to bind. Then either a wheel hops or you bust a u-joint or a CV joint. In a turn, the two rear tires travel different speeds, hence the need for a differential. The front ones are the same, but the radiuses they turn are tighter than the rear tires. So even with differentials in the axles, the two driveshafts are going to be going different speeds in a turn, But they can't, because they are locked together. If you see a vehicle with All-wheel Drive, they do have differential action in the transfer case.

Back in the 80s and 90s -- and maybe later -- New Process had a full-time transfer case that allowed all the wheels to be engaged on dry pavement, because it had a differential inside. They also had Hi-lock and Lo-lock, which locked the two driveshafts together. The difference? If you parked on ice or mud, it's quite possible that if three tires had traction but the fourth didn't, that one tire would spin and the car would just sit there. Put it in lock and two tires will turn. Have positraction or locking differentials, and you can have three or four turning the same speed, regardless of traction.

Thank you I do understand differentials I didn’t know this truck

 

[chris6563]

Just purchased a 2021 Ram 1500 Laramie 4x4. Is it good practice to engage the 4x4 periodically? Shouldn’t need it frequently, but want to make sure I’m taking the proper steps to keep it functioning properly.

 

[SpeedyV]

Just purchased a 2021 Ram 1500 Laramie 4x4. Is it good practice to engage the 4x4 periodically? Shouldn’t need it frequently, but want to make sure I’m taking the proper steps to keep it functioning properly.

I try to remember to do so every few months, at a minimum. Pick a rainy day and drive in Auto 4WD for a while...wait for a really bad weather day to do 4WD Hi for a while. I think I've only done 4WD Lo once or twice since purchasing the truck...now I have homework

 

[2020 RAM Rebel]

Hi. Just want to let people know. I have a 2020 RAM Rebel and I drive in 4 wheel HI allllllll the time, non stop! Every single day, one very single surface up to 160 km's/per hour here in Canada. Those are just the facts. So at one point BEFORE I did this I wondered if it is/was okay and if I should. Now I know it is okay for me and my truck at least and I have not had ANY problems at all. I live in a snowy climate and if I leave it in 2wd it has so much power that it just spins constantly. With 4wheel hi there is no spin. Its perfect. Don't know what else to say or type. I turn with it in 4 wheel hi all the time and I will say that turning really slowly there's something going on I think it has been defined up above in the earlier comments in this forum. It feels like the tires are gripping the road so well they just want to stay gripping in one place. So I find that I have to give it a little more gas to move it, it has such good traction. I can take a video and upload it here of my driving in 4 wheel hi anywhere and everywhere from fast to slow to turning to show anyone who truly is worried and wants to know if it can be done the proof lol.

 

[IvoryHemi]

I turn with it in 4 wheel hi all the time and I will say that turning really slowly there's something going on..... It feels like the tires are gripping the road so well they just want to stay gripping in one place. So I find that I have to give it a little more gas to move it.....”

Report back once your truck breaks

 

[Scram1500]

You only need 4wd to get moving, once in motion 2wd is fine unless you have a cinder block for a foot. My father's 1990 Cummins W350 was a widow maker in the snow, it loved to crab walk all over the place in 4wd, add standard front brakes and abs rear, a true white knuckle experience. 1000 lbs in the rear helped tremendously

 

[Scram1500]

Hi. Just want to let people know. I have a 2020 RAM Rebel and I drive in 4 wheel HI allllllll the time, non stop! Every single day, one very single surface up to 160 km's/per hour here in Canada. Those are just the facts. So at one point BEFORE I did this I wondered if it is/was okay and if I should. Now I know it is okay for me and my truck at least and I have not had ANY problems at all. I live in a snowy climate and if I leave it in 2wd it has so much power that it just spins constantly. With 4wheel hi there is no spin. Its perfect. Don't know what else to say or type. I turn with it in 4 wheel hi all the time and I will say that turning really slowly there's something going on I think it has been defined up above in the earlier comments in this forum. It feels like the tires are gripping the road so well they just want to stay gripping in one place. So I find that I have to give it a little more gas to move it, it has such good traction. I can take a video and upload it here of my driving in 4 wheel hi anywhere and everywhere from fast to slow to turning to show anyone who truly is worried and wants to know if it can be done the proof lol.

Anyone want to place bets on what gives out first?

 

[ferraiolo1]

I bet he gets even better mpg!


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