If your car was wrecked then repossessed can you use the insurance check to fix the truck or do you have to give it to the finance company?

Most likely the check will be made out to you AND the LENDER.

The insurance check will most likely have the lender name on the check. therefore, the lender will either use the check for the original intent, to have the repairs made, or keep the check and salvage the vehicle holding you responsible for any shortage in the original loan value. by the same token you should be refunded any money if the check exceed the balance of the outstanding loan.