A thorough study of SSZ-39 formation, a next generation deNOx catalyst, is presented. The presence of the trans isomer is beneficial to the growth kinetics leading to enhancements in the growth rate, in some cases of over 40%. The formation of SSZ-39 is also sensitive to the composition of the faujasite used as an aluminum source as gels with identical compositions but different faujasites do not lead to SSZ-39 formation. Once SSZ-39 begins to form, its growth rate is linear and appears to equal the rate of faujasite dissolution. Finally, the Si/Al ratio of the material is influenced by the cis/trans ratio of the SDA. These results provide new insights into the formation of this industrially relevant catalyst.