Automatic transmissions and myself have always had a strained relationship. I loved having my 5 speed tiburon for 10 years but when it suddenly died, I didn't have time to shop around for a manual trans Soul, so I opted for the 6 speed auto. I bought it at 37,100 miles. At 39,500 miles, I decided to install an aftermarket transmission cooler after the stock unit to reduce the temps some. Supposedly the optimum temperature our trannys like is around 120-140'F. I recently purchased an UltraGauge and have been monitoring the temps, and our transmissions run hot! In city driving, it can easily get up to 210'F and in highway driving it'll stabilize around 195'F.



Now remember our transmission is a "sealed" unit and is "lifetime" fluid. The lifetime is as long as the warranty is, in our case 100,000 miles. Attached is the transmission oil analysis from Blackstone labs. I took a sample of the fluid when I installed the external cooler. Blackstone commented that the fluid is breaking down already, which would make to think that the fluid would slowly destroy the transmission right around when the warranty would expire. So it would be prudent to change your transmission fluid every 40-50,000 miles and an external cooler is very beneficial for our beloved Soul's.