Does Chase use TransUnion?
It appears Chase reports authorized users to all three major credit bureaus (Experian, Equifax and TransUnion especially).
Does Amex look at TransUnion?
American Express uses all three major credit bureaus (TransUnion, Equifax and Experian) in order to assess your creditworthiness.
Do credit card companies look at TransUnion or Equifax?
In any case, the card issuer can pull your credit report with any of the three major credit bureaus — or even all of them. This means that your credit report could come from Equifax, Experian and TransUnion or any combination of these bureaus.