LCI models have issues with the transfer case actuator. If a little plastic gear fails, then no AWD. They make rebuild kits.

That said, if you can return those NAPA axles, I would. I'd rather reboot an OE junkyard axle than run any of the random aftermarket garbage. Most aftermarket axles fail VERY quickly in my experience.

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2011 M3
2006 Sierra 2500HD 4WD LBZ/Allison
2004 X5 3.0i 6MT
1995 M3 S50B32
1990 325is
1989 M3 S54B32

Hers:
1989 325iX
1996 911 Turbo