2006 Silverado 4.8 4x4 not engaging.

[sven perschmann]

There's probably already answers in here but I haven't found the same symptoms yet.

Recently my 4x4 stopped working.

Dash light still shows it coming on, actuator seems to be working - i haven't pulled it off but when switching from 2wd to 4hi vibrates and sounds like it's moving.

4Lo goes into low gears but no power to front wheels either.

There does seem to be a leak on the passenger side Axle shaft seal though.

If I identify that right? The spot where the half shaft is bolted to to the transfer case.

Any ideas and suggestions appreciated!

I'll likely take it to a garage this week anyways but would like to go in with an understanding of what's potentially going on.

Thanks in advance!

[davester]

Put the truck in 4wd while moving a little (so everything can go through the motions), then stop and lift up one of the front wheels.

 

Reach under the truck and verify that you can't rotate the front driveshaft (if you can rotate it, the TC either didn't shift into 4wd or it's broken (say, a broken chain or the mode fork is worn out).

 

Next, try rotating the wheel you lifted.  You shouldn't be able to.  If you can, then the front axle either didn't lock or it's busted.  Pull out the actuator and verify it's extended.  If it is extended, then, most likely, either the passenger side stub axle or the locking gear (this is the bit that the actuator moves to lock the axle) is broken (other bits could be broken, but these two things more commonly fail).  And make sure the actuator comes out far enough.

 

You can either unbolt the passenger side of the diff (it splits on that side, you unbolt it at the split, at the mount on the passenger frame, and the cv axle, and figure out what's wrong, or you can remove the whole diff, then split it and see what's up.  Personally, I would remove the whole diff, but that's mainly because I prefer not working under the truck and it's a little easier for me to drop the whole diff vs the oem setup (I added 4wd to my truck, and the way I did it, I can drop the diff straight down, vs rotating it around the lower driver's side mount that you need to do with the oem setup).

 

And, while you are there, you can replace the seal and probably also the roller bearing (you'll need a puller to get the old one out).