How does AUTO 4WD work/what does it do?

[mohemipar]

The best way to shift into low range is to have the truck at a very slow roll and in neutral to minimize the gears slamming. But you still use the button on there. Not sure what he was getting at?

I actually dont even know if the electronics will let you shift into low while stopped. I never tried it though.

Also remember, your engine is going to run at a much higher RPM in low.

 

[Machria]

The best way to shift into low range is to have the truck at a very slow roll and in neutral to minimize the gears slamming. But you still use the button on there. Not sure what he was getting at?

I actually dont even know if the electronics will let you shift into low while stopped. I never tried it though.

Also remember, your engine is going to run at a much higher RPM in low.

It lets you shift into 4 low when stopped, if your not in neutral, you just get a message it wont shift until you shift into neutral.

 

[Rader]

Just one question before this is put to bed, I hope. I just bought my 2017 Big Horn with Hemi/ 8 speed two weeks ago and my salesman told me I could only shift into 4 lock on the fly. I'm thinking he has to be wrong. I could see where I couldn't shift into 4 low on the fly but the other two, 4 auto and 4 lock would be fine to shift on the fly. I read through the manual and either I missed that part or they didn't mention it. And after reading all these informative posts in this thread I'm sure I'm right, I just don't want to go back to this salesman because he seemed well informed, but I'm sure he's wrong. If it sounds like a stupid question, maybe it is. I'm just not informed.

You CAN shift into 2WD, 4 auto and 4 lock on the fly or when stopped at a stop light.

 

[Machria]

Actually, you can shift the knob into 4wd Lock at anytime, going 100 mph! It's just not going to put it into 4wd lock until you are going slower and put it in neutral.

 

[Rader]

Actually, you can shift the knob into 4wd Lock at anytime, going 100 mph! It's just not going to put it into 4wd lock until you are going slower and put it in neutral.

Sorry you are wrong, I believe you are confusing 4WD lock with 4 low (range). You only have to put the transmission in neutral and stop or slow to a very slow crawl to shift into low range because it is an actual mechanical gear ratio change in the T case. Not that it ever would be necessary but for the sake of conversation....You can shift from 4WD auto to 4WD lock at the legal speed limit even in my state where the speed limit is 80 MPH.

 

[Wilytrash]

Thanks for the response. I just didn't want to wreck a brand new truck. So whatever everybody is saying is that it's fool proof and no matter what I do I won't wreck anything, it just that the transfer case won't do anything until it's safe to do it. I can shift from 2wd to 4 auto or 4 lock at any reasonable speed. If I shift to 4 low it won't anything till I'm close to a crawl.

 

[Machria]

Sorry you are wrong, I believe you are confusing 4WD lock with 4 low (range). You only have to put the transmission in neutral and stop or slow to a very slow crawl to shift into low range because it is an actual mechanical gear ratio change in the T case. Not that it ever would be necessary but for the sake of conversation....You can shift from 4WD auto to 4WD lock at the legal speed limit even in my state where the speed limit is 80 MPH.

Not sure what you are even saying? Sounds like you are saying the same thing I said, no? You can shift into 4wd Auto or 4wd Low at anytime, meaning you can TURN THE KNOB". BUT, the truck will not actually shift the tranny and/or Tcase until you are in N for lock.

 

[Rader]

Not sure what you are even saying? Sounds like you are saying the same thing I said, no? You can shift into 4wd Auto or 4wd Low at anytime, meaning you can TURN THE KNOB". BUT, the truck will not actually shift the tranny and/or Tcase until you are in N for lock.

No we were/are not saying the same thing. My reply was specific to your post #104 copied below.

Quote=Machria "Actually, you can shift the knob into 4wd Lock at anytime, going 100 mph! It's just not going to put it into 4wd lock until you are going slower and put it in neutral".

That was what I replied to as incorrect. As I said, you may have been and apparently may still be confusing or associating the term 4WD lock which works at any speed with 4WD Lo that requires the Transmission to be in N and the truck virtually stopped.

Again for clarity...In practice when driving at street or highway speed with the transmission in D and with the T case in 2WD or in 4WD Auto mode if you press the 4WD lock button in a split second the clutch in the T case is in the 4WD LOCK mode. The detail that confuses some is lock in a 44-44 just makes the clutch behave differently, it is accomplished electrically, nothing mechanical shifts so it is not speed sensitive.

 

[Machria]

No we were/are not saying the same thing. My reply was specific to your post #104 copied below.

Quote=Machria "Actually, you can shift the knob into 4wd Lock at anytime, going 100 mph! It's just not going to put it into 4wd lock until you are going slower and put it in neutral".

That was what I replied to as incorrect. As I said, you may have been and apparently may still be confusing or associating the term 4WD lock which works at any speed with 4WD Lo that requires the Transmission to be in N and the truck virtually stopped.

Again for clarity...In practice when driving at street or highway speed with the transmission in D and with the T case in 2WD or in 4WD Auto mode if you press the 4WD lock button in a split second the clutch in the T case is in the 4WD LOCK mode. The detail that confuses some is lock in a 44-44 just makes the clutch behave differently, it is accomplished electrically, nothing mechanical shifts so it is not speed sensitive.

Well sorry, that is NOT how mine works. I can put the selector on 2wd, 4wd Auto, 4wd Lock, or 4wd Lo at any speed. I'm not saying it shifts, I'm saying you can hit th4e buttons, the light blinks and the display in front of me says the truck will not shift until I put it in Neutral for 4wd Lo, or slow enough (I believe it is 35mph) for 4wd Lock, and it always switches for 4wd Auto. I understand the part about the clutches, and the electronic semi-lock not "really" locking as other trucks do. But I can click any of the buttons/selectors at any time, they just don't shift until all the parameters are met in the software....

I can add, it is the same for the Raise / lower buttons for the airbags.

 

[Wilytrash]

So if I'm understanding this right I can go back and forth from 2wd to 4auto on the fly. If I go to 2wd to what they call 4lock I have to slow down to 35mph to really make the switch. 4low I must be in neutral and either stopped or at a crawl to make the switch from 2wd, 4auto or 4lock. And I assume vice versa.

 

[nick84]

So if I'm understanding this right I can go back and forth from 2wd to 4auto on the fly. Correct.

If I go to 2wd to what they call 4lock I have to slow down to 35mph to really make the switch. Partially correct. 4 Lock is a program difference from 4 Auto, with no change in mechanical parts, simply a different control for the clutch inside the T case. Possible to do I believe, but not advised to drive at speed in 4 lock.

4low I must be in neutral and either stopped or at a crawl to make the switch from 2wd, 4auto or 4lock. Correct.

And I assume vice versa.

 

[VA10]

2hi to 4hi/4lock - shift on the fly

2hi or 4hi/4lock TO 4lo - Stopped and in neutral shift OR very very slow crawl. I prefer complete stop to shift into 4lo.

Vice versa for getting out of 4lo.

 

[Machria]

2hi to 4hi/4lock - shift on the fly

2hi or 4hi/4lock TO 4lo - Stopped and in neutral shift OR very very slow crawl. I prefer complete stop to shift into 4lo.

Vice versa for getting out of 4lo.

Exactly. So basically the only thing you can't do on the fly is shift into, or out of "4wd Lo".

 

[Rader]

So if I'm understanding this right I can go back and forth from 2wd to 4auto on the fly. If I go to 2wd to what they call 4lock I have to slow down to 35mph to really make the switch. 4low I must be in neutral and either stopped or at a crawl to make the switch from 2wd, 4auto or 4lock. And I assume vice versa.

You do not need to slow down to 35MPH to shift into 4WD lock and have the lock mode complete, that is flat out rubbish, also the claim made prior to that, basically "the transmission must be in neutral when you shift into 4WD lock" is also rubbish.

Other than needing to stop or slow to crawl and put the T case in N to shift into 4WD low the only note on speed limit for 44-44 T cases has to do with top speed when driving in low range and what it says is "do not exceed 25MPH in low range". Their voiced concern is that over 25mph might over rev the engine, if you watch the tachometer you can take that warning with a grain of salt.

I live a few mile in on a steep dirt road that turns off in the middle of a Rocky Mountains pass at 6,200 ft elevation. At times it is impossible for me to go over the pass to town or get home without 4X4 so I have shifted my truck into 4WD lock at highway speed a thousand times and the indicator light virtually instantly goes solid show that 4WD lock is engaged and for proof if it was not engaged I would not make it up the pass LOL.

IMO If someones truck is not completing a mode change into 4WD lock at highway speed it possibly has an electrical problem with a speed sensor or something like that, or the front and rear tires are mismatched enough that the speed sensors think there is wheel slippage/spin so it will not shift.

Below is directly from the owners manual for my 2015 Bighorn EcoDiesel. Note in high range modes you can shift stopped or moving. There is NOT a mention of a top speed for shifting into 4WD lock or 4WD auto. Their is a note that if you are in 2WD and the rear wheels are spinning it will not shift into 4 auto or 4 lock until you stop spinning the wheels. If a person has ever tried to shift a conventional manual T case from 2WD into 4WD with the rears spinning you know exactly why they check front rear speed sync before shifting LOL.

8 SPEED TRANSMISSION

Five-Position Electronically Shifted Transfer Case
(Eight Speed Transmission Only)

2WD To 4WD AUTO Or 4WD LOCK

Push the desired position on the 4WD Control Switch to shift the transfer case. Shift between 2WD and 4WD AUTO and 4WD LOCK can be done with the vehicle stopped or in motion. With the vehicle in motion, the transfer case will engage/disengage faster if you momentarily release the accelerator pedal after selecting the desired position on the control switch. If the vehicle is stopped, the ignition switch must be in the ON position
with the engine either running or OFF. This shift cannot be completed if the ignition switch is in the ACC position.

NOTE: The four-wheel drive system will not allow shifts between 2WD and 4WD AUTO/4WD LOCK if the front and/or rear wheels are spinning (no traction). In this
situation, the selected position indicator light will flash and the original position indicator light will remain ON. At this time, reduce speed and stop spinning the wheels
to complete the shift.

 

[Machria]

Other than needing to stop or slow to crawl and put the T case in N to shift into 4WD low the only note on speed limit for 44-44 T cases has to do with top speed when driving in low range and what it says is "do not exceed 25MPH in low range". Their voiced concern is that over 25mph might over rev the engine, if you watch the tachometer you can take that warning with a grain of salt.

It's NOT a warning on my truck, it will not allow it to shift. The display simply says in the LCD display something like "Truck will not shift into 4wd Lo until below 5mph and in N".

I'll go out and take pictures for you....

 

[muddy12]

It's NOT a warning on my truck, it will not allow it to shift. The display simply says in the LCD display something like "Truck will not shift into 4wd Lo until below 5mph and in N".

I'll go out and take pictures for you....

Think you guys are saying the same thing [emoji106]
2wd to 4auto = turn dial at any speed.
4auto to 4lock = turn dial at any speed.
4lock to 4lo = stopped or rolling under 5mph with trans in neutral.


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[Rader]

It's NOT a warning on my truck, it will not allow it to shift. The display simply says in the LCD display something like "Truck will not shift into 4wd Lo until below 5mph and in N".

I'll go out and take pictures for you....

Please....Before taking issue read well and do your best to understand the conversation before replying to a post of mine then interpolating it to a topic that is not in question.

OF course your T case will not shift into 4WD lo with the automatic transmission in drive or with the truck rolling over a few MPH. That is not specific to this truck or this T case. The warning message we ALL have noticed on our trucks is just the modern equivalent of idiot lights. The message is for people that are not thinking or are aware of the inner working of T cases with low range. Just in case some reading this other than you have not given this though and wonder why an automatic transmission MUST be in N before shifting to low range this is why.

When the transmission is NOT in neutral the transmission output shaft is powered, the shaft is turning at the engine speed minus reduction equal to the gear it is in. So the transmission is trying to spin the T case input and it will spin it up as soon as the T case is between gears. Because of that any attempt to shift the low range sliding gear that is not turning or slowly turning into another gear that is powered and spinning at hundreds of RPM will be extremely loud and possibly not end well for the T case or some parts downstream.

 

[LouM]

Ah, for the days of one or two sticks coming up from the floor for the t-case and then another one for most trannies.

 

[madweazl]

... Because of that any attempt to shift the low range sliding gear that is not turning or slowly turning into another gear that is powered and spinning at hundreds of RPM will be extremely loud and possibly not end well for the T case or some parts downstream.

Wouldn't this preclude it from shifting into 4Lo while rolling as well?

 

[muddy12]

Wouldn't this preclude it from shifting into 4Lo while rolling as well?

While this is mostly true, the gears in a t-case are typically not synchronized. Because of this, some rotation is needed to get the gears to mesh properly. Rolling slowly (less than 5mph) provides the rotation for a smooth mesh, and putting the trans in neutral takes strain off of the system.


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