99 astro awd system not working properly

i am having problems with my awd. drove through a lot of snow, next morning went to leave and the front left wheel was froze up. finally got it freed up and the awd does not work, the t-case motor is good the t-case modual is good. with the t-case motor off , can take a 6 inch wrench and move about 1 to 1 1/2 inches. to engage the clutches. i have 2 codes but they are in the history, awd light only comes on when excessive spin of tires. codes are co310, co374. does the awd system use the abs sensor in the hub to engage the awd system?

....does the awd system use the abs sensor in the hub to engage the awd system?

Yes. The TCCM uses the vehicle speed sensor and wheel speed sensors to determine if there are any differences in wheel speeds before engaging AWD.

thanks any idea about the codes or where i can find the definitions? and how about a manual on the awd systems?

C0310 indicates a circuit problem for the encoder motor, (mounted on the transfer case). Here's the link to the diagnostic flow chart: http://www.justanswer.com/uploads/MCVGreg/2007-07-25_202958_1999-Tahoe-C0310-Debug.pdf

C0374 is "General System Malfunction" which was most likely the second DTC you retrieved. Repairing the C0310 will probably clear the C0374.

As for a manual, don't fool around with aftermarket books, go to the GM website and order the Shop Manual for your vehicle. http://www.helminc.com/helm/product2.asp?class%5F2=CHV&mk=Chevrolet+%26+Geo&yr=1999&md=Astro&dt=Shop%2FService+Information&module=&from=result&Style=W49ZX0CHESLB971&Sku=GMT99ML&itemtype=N&mscsid=U2SAEFASBE178KNC41149445U72X9ME3