4X4 Drivetrain Question

[RainDodger]

Howdy... I have a question regarding the functionality of the 4X4 drivetrain. 2019 1500 Classic, Bighorn. I've got the 8-speed tranny.

One of the selections for my 4X4 system is "4WD-Auto". I understand what it is, but the manual doesn't tell me exactly what's going on. Can anybody tell me what's actually rotating in the 4WD-Auto mode? Is the front driveshaft rotating and the front wheels are just unlocked unless there's some traction slippage, or is the front driveshaft not rotating and powering the front diff unless there's a traction problem.

I'd just like to know what I'm putting stress on when I select 4WD-Auto... as in, what portion of the front drivetrain is powered up when there's wheel slippage?

Thanks, guys.

Roger

 

[Toddbigboytruck]

Great question I will stay tune for more.

I have a similar truck. I drive 2wd 98% of the time 4x4auto when the roads are covered. 4x4hi. Haven’t needed it 4x4low used 5 times in backing the trailer in to hard places

 

[Ridgerunner665]

The front end is always engaged, as in the hubs are locked...always.

In 4 auto the clutch in the transfer case doesn't engage to send power to the front end until the sensors detect rear wheel spin.

In 4 lock the clutch in the transfer case is electronically engaged, but may take a little rear wheel spin to get everything lined up and locked.

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[Brandon-w]

So I Beleive you have the Borg warner 44-44 t case which is clutch activated. 4 auto basically let's the rear tires rotate x amount of times before electronically activating the clutches. Once no rear slip is detected it unlocks the clutches and off you go again. In any 4x4 selection the front diff is actuated.

The problem is in what they call "4lock" it doesn't really lock. It acts like 4 auto but your tires say rotate once or twice and then it activates and then unlocks again.

https://www.ramforum.com/threads/transfercase-diagram.55161/
Here's some more reading.

 

[MRFREEZE57]

it is sort of engaged but in 2wd the right front axle is disconnected by a solenoid from the differential where as the left front is still turning the spider gears but not the carrier. I was concerned about the extra drag caused by this and locking hubs are not much available however another guy on the forum explained it good with a schematic showing there is minimal parasitic drag in 2wd. I think in 4w auto the right axle is engaged and would cause more drag. I wish that there were sources for hubs so the front wheels would just be free spinning when in 2wd so not turning the cv joints or the spider gears.

 

[Brandon-w]

it is sort of engaged but in 2wd the right front axle is disconnected by a solenoid from the differential where as the left front is still turning the spider gears but not the carrier. I was concerned about the extra drag caused by this and locking hubs are not much available however another guy on the forum explained it good with a schematic showing there is minimal parasitic drag in 2wd. I think in 4w auto the right axle is engaged and would cause more drag. I wish that there were sources for hubs so the front wheels would just be free spinning when in 2wd so not turning the cv joints or the spider gears.

If I could find a good hub kit I'd have someone build a spool for the zf215 front end and have it locked solid when I needed it. [emoji16]

 

[Ridgerunner665]

Mine doesn't unlock in 4 lock or 4 low... wheel spin or not.... once it locks its locked until I take it out of 4 lock or 4 low....or turn the ignition off.

I played with this extensively this past weekend in a muddy field.

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[Brandon-w]

Mine doesn't unlock in 4 lock or 4 low... wheel spin or not.... once it locks its locked until I take it out of 4 lock or 4 low....or turn the ignition off.

I played with this extensively this past weekend in a muddy field.

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You likely have the Borg warner 44-45 I'm guessing you don't have the auto option only 4 and 4low right?

 

[Ridgerunner665]

Nope...its a 44-44....4wd auto.

2018 1500 Big Horn, 5.7 Hemi, 3.92 limited slip.

It behaves as you describe in 4 auto... unlocks when the rear gets traction... but not in 4 lock or 4 low, it stays locked once it locks, it can take a little spin to get it lined up and locked... but once it locks it stays until I take it out of 4 lock or 4 low, or turn the ignition off which kills the power to the clutch actuator.

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[MRFREEZE57]

If I could find a good hub kit I'd have someone build a spool for the zf215 front end and have it locked solid when I needed it. [emoji16]

that would be the set up I would want as I never plan on using the 4auto and it is so easy to engage a set of hubs when needed and free spin for when in 2wd.

 

[Ridgerunner665]

I had a full time 4wd 1979 Chevy half ton, I bought it used for $800, it had been used for nothing but a farm truck for years before I bought it....I replaced the bearing in the back of the right front spindle and that outer axle, rebuilt the engine.... and drove it every day for 14 years after that with nothing more than routine maintenance... and I wasn't easy on it either (18 years old when I bought it)... the drive train was still solid when I sold it, but the body was falling apart.

The front end being locked will cost some MPG.... but I don't believe there is any extra wear and tear to be worried about.

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[MRFREEZE57]

I had a full time 4wd 1979 Chevy half ton, I bought it used for $800, it had been used for nothing but a farm truck for years before I bought it....I replaced the bearing in the back of the right front spindle and that outer axle, rebuilt the engine.... and drove it every day for 14 years after that with nothing more than routine maintenance... and I wasn't easy on it either (18 years old when I bought it)... the drive train was still solid when I sold it, but the body was falling apart.

The front end being locked will cost some MPG.... but I don't believe there is any extra wear and tear to be worried about.

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the only thing is you are turning all of that drive train when not needed, that will also cause faster front tire wear.

 

[Ridgerunner665]

Yes...it is harder on the tires on a true full time system like was in the Chevy.

Those were always in 4wd.... these new ones though being unlocked like they are don't suffer from that.

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[MRFREEZE57]

Yes...it is harder on the tires on a true full time system like was in the Chevy.

Those were always in 4wd.... these new ones though being unlocked like they are don't suffer from that.

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had my front end jacked up the other day and spun the wheels, they actually do spin quite easily and feel very minimal drag.

 

[Tim Garceau]

Everything is easily replaceable, just drive the ******* thing. Especially under warranty, too many panties in a bunch.

 

[Wild one]

If you lower or lift your 4X4 the CV drag increases noticeably.My little lowered 4X4 gained close to 2/10's at the dragstrip by pulling the front axles .The CV's don't turn for free and if you put them into a bind situation by lowering or lifting your 4X4 they start to rob horsepower.The CV axles are 40lbs of rotating weight and it takes power to turn rotating weight,it'd be nice if they did have the option to unlock them via an unlockable hub,it'd also save wear and tear on them.

 

[James OBrien]

I love learning about this stuff, one area I don't completely understand and appreciate the info. However the 4x4 works, the 4 Auto is perfect for me in the snow but you have to know how to goose it just right to kick things in and power through. The 4 lock does seem to lock MUCh quicker and then not disengage until you shift out.

 

[RainDodger]

Going back to the earlier part of this thread, the 8-speed tranny is made by ZF (Germany)…. which probably has no bearing on what the front driveline is doing.

 

[Wild one]

Going back to the earlier part of this thread, the 8-speed tranny is made by ZF (Germany)…. which probably has no bearing on what the front driveline is doing.

ZF also builds the front and rear diffs,they quit using AAM diffs in 2011.

 

[2019RamInSC]

I had a full time 4wd 1979 Chevy half ton, I bought it used for $800, it had been used for nothing but a farm truck for years before I bought it....I replaced the bearing in the back of the right front spindle and that outer axle, rebuilt the engine.... and drove it every day for 14 years after that with nothing more than routine maintenance... and I wasn't easy on it either (18 years old when I bought it)... the drive train was still solid when I sold it, but the body was falling apart.

The front end being locked will cost some MPG.... but I don't believe there is any extra wear and tear to be worried about.

Sent from my SM-G960U using Tapatalk

I had the same truck in a 78 model. 400 ci small block. It was a terrific truck!