246 transfer case no power to front wheels 4x4 slip?

[W8MCC]

1998 suburban 1500 4x4 5.7 4l60e np246 push button 4x4 2/4hi/4lo/auto

 

I need some help here. Suddenly my 4x4 quit working on my truck, details above.  I have diagnosed everything I can. There are no codes or lights.

 

The issue is no power to the front wheels while in any of the 4x4 positions. The front axle actuator is working, checked with a new one.  The encoder motor is new, just installed oem motor.

 

When the truck is on stands the front wheels roll in 4x4 but on the ground they have no torque.  I put the front on the ground and jacked up the rear axle, the rear tires spin in drive, the fronts have no pull what so ever.

 

With the truck in the air, 4x4 hi engaged, engine off, truck in neutral, I can roll the front drive shaft by hand and see movement in the rear shaft.  Again, when it's in the air everything works, only on the ground it acts like it's still in 2wd.

 

Does the 246 have slipping issues? Is that even possible? I've never had one apart but if there's discs to engage them possibly they are worn?

 

My next step is a xfer case but I don't want to throw any more money away.

 

I should mention I have this problem in auto mode too.

 

Thanks

[W8MCC]

2 hours ago, mjm-1957 said:

Take the rubber plug out on the tail housing and get a mirror and a light and see if the snap ring that holds the rear output bearing is still in one piece. That snap ring can break and let everything move rearward and possibly cause the issue you are having.

Plug out, snap ring normal

[mjm-1957]

Guess your going inside.....

[carkhz316]

7 hours ago, mjm-1957 said:

The oil pump is only there to provide lube oil. The clutch pack only is used in auto 4wd.

You are correct on the oil pump, though the clutches are used for all front output. For 4H/ 4L, the shift fork just fully applies the clutch pack ignoring front output speed, whereas in Auto, it modulates the apply pressure to vary the output speed as conditions/ slippage demand. There is no direct mechanical coupling like the synchro and gear assembly in the 261/263 variants.

 

 

So to OP, having one of the ranges work but not the others would indicate it's NOT a issue with the clutches. 

Edited January 19, 2019 by carkhz316

[W8MCC]

8 hours ago, carkhz316 said:

You are correct on the oil pump, though the clutches are used for all front output. For 4H/ 4L, the shift fork just fully applies the clutch pack ignoring front output speed, whereas in Auto, it modulates the apply pressure to vary the output speed as conditions/ slippage demand. There is no direct mechanical coupling like the synchro and gear assembly in the 261/263 variants.

 

 

So to OP, having one of the ranges work but not the others would indicate it's NOT a issue with the clutches. 

All of the front wheel assist ranges do not work. I'm swapping the xfer this morning.

[W8MCC]

17 hours ago, mjm-1957 said:

Guess your going inside.....

Case is out. Something obviously busted internal. Ratchet sound from inside case in neutral on the bench. When selector turned past 4 hi clockwise into the spring tension zone of the fork, selector cocks into case at an angle. New one going in. Post pictures of internals later after I get it wrapped up.

[4321]

final outcome? i have the same issue as we speak.

[jjordan9773]

How is it working now? Mine is doing the same thing. 263hd transfer case but the exact same issue you were having. 

[subu1500]

SOLVED



Had the same issue as (OP) W8MCC. 
My encoder motor gears where stripped. (cheap aftermarket encoder).
It was stripped because the needle bearing in the Tcase was bad. That bearing holds the splined shaft for the encoder motor.  Bad bearing = play. Play = crooked engagement and stripped gears under load. Split T case apart, changed bearing. ( Can probably change the bearing without splitting the Tcase next time.) Got a used GM encoder, bolted back up. Works like new.