Assuming automatic transmission... first/ easiest step is always check your fluid level: Engine running in park. Is the check engine light or Service 4WD light on? Good chance it is transfer case or t-case control module issues: For some reason it could be shifting itself into neutral.
1996 gmc sierra truck, 4wdr. 4.3l. Won't go into no gears...
No lights on dash just abs light
It kinda of slips in 2 gear, then nothing
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