The QR25 gen4 Altimas mostly didn't have heat exchangers in the radiator (the VQ35's did), so they overheat easily when the fluid gets raunchy. You can tell easily if your ride has an exchanger, if the "beehive" cooler on the tranny has four tubes then it has one, if it has two tubes then the tranny has no cooling. To add a cooler to a 2-port trans you need to replace the beehive with a 4-port version. That isn't a big deal, there are tons of aftermarket 4-ports on eBay and Amazon in the $35~50 range and a good Hayden cooler can be had for around $50. The real question is whether your tranny can be saved if it has been overheating. The fluid has to be in really sad shape if it's going into protection on a constant basis. That's another thing CVTz50 can help you with, it can read the CVT-A/CVT-B values stored in the TCM, which are basically an overheat record. On a healthy trans they should both be zero, any positive number indicates the number of times the fluid has cooked. If you see big numbers then chances are the tranny is shot, if you see numbers less than about 15~20 then it's worth trying to save it with fresh fluid.