You have the 4L60E, electronic version of the Old 700R-4. Many places should have what you need, even ebay. https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2057872.m570.l1313.TR1.TRC0.A0.H0.X2004+GMC+Envoy+transmission.TRS0&_nkw=2004+GMC+Envoy+transmission&_sacat=0
Buy transmission or get one rebuilt
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