Need some clarification on 4WD Auto Mode

[mbarber84]

How does Ram achieve this setting? Are they using a front axle disconnect like the HD’s or do they have some sort of partial engagement of the transfer case? I would assume they have the driveline prepared to transfer power when the transfer case clutches engage once wheel slip is detected? Anyone happen to have the technical manual and can post a picture of the theory of operation for this system?

 

[HSKR R/T]

How does Ram achieve this setting? Are they using a front axle disconnect like the HD’s or do they have some sort of partial engagement of the transfer case? I would assume they have the driveline prepared to transfer power when the transfer case clutches engage once wheel slip is detected? Anyone happen to have the technical manual and can post a picture of the theory of operation for this system?

Front diff locked in. Clutches in transfer case that will transfer power to front axle when rear wheel spin is detected.

 

[mbarber84]

Front diff locked in. Clutches in transfer case that will transfer power to front axle when rear wheel spin is detected.

So there is indeed a disconnect in the front axle that engages when in 4WD auto and disengages in 2WD mode?

 

[HSKR R/T]

So there is indeed a disconnect in the front axle that engages when in 4WD auto and disengages in 2WD mode?

Yes, and it's a somewhat common failure item if you are getting service 4wd lights and it won't shift into 4wd. I replaced axle lock actuator earlier this year.

 

[mbarber84]

Yes, and it's a somewhat common failure item if you are getting service 4wd lights and it won't shift into 4wd. I replaced axle lock actuator earlier this year.

Thanks that made sense in my head, but I had a bunch of idiots trying to convince me that running it in 4WD auto was “the same as 2WD unless it detects wheel slip” and I knew that couldn’t be right. Has to have an axle disconnect or something. I appreciate the confirmation. That connection being engaged would probably be sufficient enough drag to slightly decrease fuel mileage.

 

[HSKR R/T]

Thanks that made sense in my head, but I had a bunch of idiots trying to convince me that running it in 4WD auto was “the same as 2WD unless it detects wheel slip” and I knew that couldn’t be right. Has to have an axle disconnect or something. I appreciate the confirmation. That connection being engaged would probably be sufficient enough drag to slightly decrease fuel mileage.

Yes, on my truck it's about a 1.5mpg hit.