I got the wife a new 2018 surburban a few weeks back and was driving today and the transmission temps seemed a little high. Truck is the 5.3 with 3.42s included with the tow package. Ambient air temp was 55* and the trans was 189* while cruising down the highway at 72-75mph. Just seemed high since I normally expect to see +100* over ambient as the norm. Does anyone know anything about these transmissions? Is this the norm? Currently has 600 miles on it so I’d rather catch it early if there is a problem.