4WD Disengagement Issue

[bmborum]

2012 CCSB ST, 4WD in the floor. 115k miles.

Ran into some odd issues where when you put it in 4H I got a real low hum (not a grinding sound) from the transfer case that would sortve progressively get louder to a point then just kind of stay there. Once this started it wouldn't easily come out of 4H back to 2H unless it was in neutral for an extended period, were off the throttle for an extended period, or you put it in reverse. Noticed a leak in the pinion seal in the front diff. Drained the transfer case, fluid looks okay and had no metal in it. Front diff fluid looked okay and had to excess metal in it. Visually inspected the gears and they looked normal. Top it off with fluid and it made a modicum of difference but then it backslides and now just sounds unhealthy. When in 2H at a real low speed like approaching a stop sign you can hear almost like the front end isn't fully disengaged....

The only thing I haven't done is remove the front drive shaft and put it into 4WD to see if it's a diff problem or a transfer case issue

I am sure something is shot to hell at this poi t and didnt know if the knowledge of this forum might be able to point me in a direction before I take it to someone.

 

[jhenderson]

Naturally, I can't say anything about a noise I can't hear, but transfer case disengagement sounds normal. Not knowing where you live or how often you use 4wd it's hard to say. If you use it every day, the case works pretty easy. Every month or less,not so much. The drivetrain has to be completely unloaded for it to come out of 4wd. That means off the throttle but no deceleration loads. Possibly full stop then reverse. Transfer cases are pretty stout and don't usually have problems as long as they have lube. If the front end lube looked good I'd be looking at the Cardin joint in the front shaft.

 

[kthaxton]

Forgive me for asking....but what kind of surface were you driving on when this occurred?

 

[DonFitzwater]

My 2016 makes a noticeable whirring noise in 4x4 that drives me crazy (dealer says normal so will run it until something grenades and or falls off and they can fix it). It also won’t come out of 4x4 unless driven for some distance or if I put it in reverse, it will come out immediately. This is normal behavior compared to my past 2015, 2014 and 2010 transfer cases.

 

[bmborum]

I’m aware the driveline has to be unloaded but traditionally it’s been let off the throttle for a split second and it completely disengages. Now, we are like let off the throttle and coast for 200-300 yards before it disengages OR pop it into neutral.

I have a notion it’s this Cardin joint in the front drive shaft....

 

[bmborum]

Loose to packed snow on pavement

 

[bmborum]

This is beyond a normal noise...

It’s not a grinding noise....it’s just a very loud hummmm but beyond what’s normal. It’s most obvious when it’s engaged and then barely obvious when it’s disengaged