I assume that by improve your credit, you mean improve your cedit score. The answer is no. FICO scoring is not based on loan terms, other than amount and type of the loan and existing monthly balance remaining on the loan. They dont give a hoot about legal responsibilities in the case of loan default. FICO is a measure of monthly payment risk, and not financial status.
And as has been said, you cannot "drop" a co-signer, for that was a legal condition upon which the loan was placed. To get the co-signer off, you will have to re-finance a new loan.
No creditor will see any advantage to simply agreeing to remove a co-signer, for it just reduces their ability to collect upon any default.