1999 Chevy Astro front transfer case

I am going to try to help you to the best knowledge of my ability. To answer your question, you can't.

I have had 2 AWD Astro's. I asked a dealer service tech one time, "just what does AWD mean?"

It was explained to me like this: During normal driving conditions, you have 80% pull power to the rear wheels and 20% to the front. If the rear wheel ABS sensors detect a slippage of a rear wheel, then 80% of the pull power is shifted to the front wheels. This can happen several times a second.

Now I can tell you that my AWD Astro would climb through 25 inch snow banks, uphill, with no problem and that if dozens of people were in line to un-successfully try to climb an icy hugh hill, I could just run around them like nothing.

I think you would get a check engine light if some part of the AWD failed.

By the way. I wanted to check out how good this Anti-Lock Braking system was. I took the van out on flat ground in the country with smooth shoulders on both sides. I didn't care if I ran off the road. I ran it up to 60mph and just mashed and buried the brake pedal. It
only shifted 6 inches to the right in nearly an eighth mile. I was VERY impressed,

Just trying to be helpful.

Ken