A 2013 Infiniti JX35 transmission replacement costs will vary depending on the mechanic you use, the area you live in, the quality of the replacement parts, and a dozen or so other minor factors. Speaking broadly, though, you should expect the job to cost between $6,500 and $7,000 for parts and labor.
With a big job like that, it’s always a good idea to compare quotes from multiple auto shops before deciding on one—that way you can be sure that you’re getting the best available price.