Jump to content

4wd operation information

marine6680

By marine6680
in Engines & Drivetrain

Recommended Posts

marine6680 New Member

marine6680

Posted
Posted

Looking for some technical information regarding the 4wd system in my '16 LTZ Z71.

I like knowing what the truck is doing when the system is engaged.

 

So far, I think I have a bit figured out.

 

Being an electronic system, the transfer case uses clutch packs to engage 4wd modes rather than meshing gears. This is how they accomplish a smooth shift on the go 4wd, and what allows the auto mode to work smoothly.

The rear diff is auto locking, and will lock up when slip is encountered. (left to right) Normally it acts more like an open diff.

In "auto" mode, the transfer case is sending power to the rear diff, and when it senses slip, it activates the (I'm guessing electrically controlled) clutch inside the transfer case to send power to the front diff.

The front diff has an "actuator" that engages the diff somehow... not 100% sure the technical details, but I get the sense that the front diff is decoupled left to right, its not even acting like a simple open diff, the left and right axles are independent unless the actuator is engaged... Is that right?

This front diff actuator must engage for 4wd use. In auto mode, it is engaged full time, but the transfer case is not sending any power to the front diff until needed. During normal 4wd mode, the actuator is engaged full time, with power being fed from the transfer case.

 

I am not sure what kind of diff the front is... Is it an open or some type of limited slip, or auto locking... A limited slip or auto locking seems most useful and likely to be what it is... but I could be wrong, I have seen trucks with an open front diff, and my truck could be no different.

 

To me, having the front wheels receiving power, but only the front wheel without traction getting that power seems like you might as well not even have 4wd. If you have a front tire and rear tire on ice while stopped, seems a 4wd system without a limited slip diff in the rear and front, or auto locking or manual locking, would just sit and spin... Or what if only one front tire had any traction... same thing.

My main question about the technical details mostly fall around the front diff, what type it is, and what the actuator does... But if I have any of the other details wrong, let me know.

 

Thanks

HondaHawkGT Senior Enthusiast

HondaHawkGT

Posted
Posted

Looking for some technical information regarding the 4wd system in my '16 LTZ Z71.

I like knowing what the truck is doing when the system is engaged.

 

 

So far, I think I have a bit figured out.

 

Being an electronic system, the transfer case uses clutch packs to engage 4wd modes rather than meshing gears. This is how they accomplish a smooth shift on the go 4wd, and what allows the auto mode to work smoothly.

The rear diff is auto locking, and will lock up when slip is encountered. (left to right) Normally it acts more like an open diff.

In "auto" mode, the transfer case is sending power to the rear diff, and when it senses slip, it activates the (I'm guessing electrically controlled) clutch inside the transfer case to send power to the front diff.

The front diff has an "actuator" that engages the diff somehow... not 100% sure the technical details, but I get the sense that the front diff is decoupled left to right, its not even acting like a simple open diff, the left and right axles are independent unless the actuator is engaged... Is that right?

This front diff actuator must engage for 4wd use. In auto mode, it is engaged full time, but the transfer case is not sending any power to the front diff until needed. During normal 4wd mode, the actuator is engaged full time, with power being fed from the transfer case.

 

I am not sure what kind of diff the front is... Is it an open or some type of limited slip, or auto locking... A limited slip or auto locking seems most useful and likely to be what it is... but I could be wrong, I have seen trucks with an open front diff, and my truck could be no different.

 

To me, having the front wheels receiving power, but only the front wheel without traction getting that power seems like you might as well not even have 4wd. If you have a front tire and rear tire on ice while stopped, seems a 4wd system without a limited slip diff in the rear and front, or auto locking or manual locking, would just sit and spin... Or what if only one front tire had any traction... same thing.

 

My main question about the technical details mostly fall around the front diff, what type it is, and what the actuator does... But if I have any of the other details wrong, let me know.

 

Thanks

Auto 4WD - Transfer case sends a little power to the front all the time (approx 10% is the most common claim I have read). Reacts extremely fast to send more power to the front when the wheel speed of the two wheels is less than the equivalent speed of the output shaft sending power to rear axle.

4WD HI/LOW- Transfer case is locked in and power is split 50/50 like a standard 4WD system.

 

The front diff is an open diff all the time. Rear diff is a locking diff that engages automatically via a governor mechanism. It engages when there is a 100 RPM differences between the left and right rear tires. It will unlock when you reach roughly 30 MPH or stop and move in reverse for a short distance.

slee3247 Enthusiast

slee3247

Posted
Posted

If these trucks are the same as the earlier ones, there's a solenoid that acts as a front axle disconnect. Basically, it's a solenoid that pushes a synchroniser assembly onto the axle which has matching teeth. This locks the axle to the differential. However, the front differentials are open style on these trucks.

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.

  • Forum Statistics

    250.6k
    Total Topics
    2.7m
    Total Posts

  • Member Statistics

    342,993
    Total Members
    8,960
    Most Online
    President Roberto
    Newest Member
    President Roberto
    Joined

  • Who's Online   0 Members, 0 Anonymous, 209 Guests (See full list)

    • There are no registered users currently online

  • Latest Articles

  • Posts

    • bwiese
      upgrading speakers on 2026 std cab WT...

      By bwiese · Posted

      I don't wanna do major surgery/upgrades, behind-the-dash work, add amps, change radio etc. on my '26 std cab WT. On the WT, it has the base 7" IOR infotainment setup, and only two speakers (doors). Since I listen to classical, looked around for speakers that do well and dug thru reviews. Two-way speakers were found to be better than 3-way. So I've ordered a pair of  Infinity Reference REF-9632IX 2 way speakers.  [These may  or may not have been discontinued / succeeded by the 3-way ...9633 ones.]    These speakers are lauded for 3 ohm and 94db sensitivity spec so they'll work well for ordinary base car radios without amps and offer better performance (quality,  strength) than  default base paper-cone speakers. They'll be installed in a few days and I'll let y'all know what I think. Bill W San Jose      
    • RyanbabZ71
      RyanbabZ71's 2019 High Country

      By RyanbabZ71 · Posted

      Thanks!   Changed out the rear shocks today to Bilstein 5100s.  So far feel much better. The stock Rancho were wore out.  Lots of heavy hauling (2 moves, home renovations, etc).  Next up is new BFG tires Monday.  Cant wait the current tires have little to no wet traction and are super loud (hum)    
    • Snowcamo
      No high speed fans...

      By Snowcamo · Posted

      Ok, I got the all the codes. What do you all think would be a place to start?
    • Chuck FB
      Correct way to service 2024 l8t allison trans?

      By Chuck FB · Posted

      How about I just point to the factory pans stand pipe little drain plug and claim its a pan with a real drain plug !. I just couldn't swallow the fact that a Dorman pan which at this point is probably the only pan out there that fits the gas version truck cost that much up here in Canada so I decided initially anyway to skip it and see what I thought of pulling the pan method and down the road if I felt inclined enough then I would either install a drain plug kit in the factory pan if there is enough room for it, or have a bung welded onto it, or put an aftermarket pan on. The thing is if the pan is not pulled then the magnets in the pan can't be inspected and cleaned or if wanting to change out the filter. However of course it certainly would make the job easier to be able to drop the oil first before having to handle the pan if dropping the pan that go around was the goal.    I knew a guy locally that was doing custom field spraying years ago with a pickup pulling a ground driven sprayer, I believe it was a GM pickup with an automatic trans. He had a drain plug in his pan and would drop the oil out of it once a week and top it back up through the dipstick tube to keep refreshing a portion of the oil often and that made the transmission last far longer than had he done nothing. Soft fields pulling 500 gallons of water at the start of each mixed up sprayer tank batch and in low range sucking along. I imagine he got some tips from other custom sprayer outfits doing the same thing at the time and learning from their blown up tranny mistakes. Transmissions then had no lock up converter so would cook the crap out of the fluid slipping that much and it would not have been synthetic fluid either. 
    • KARNUT
      Gas Prices

      By KARNUT · Posted

      3.39 Kroger’s in Montgomery Texas. 

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...