I have seen some posts about the transmissions on the ML 320 going out early. I had 30,000 of VERY easy driving mixed equally between city and highway and mine needed to be rebuilt at 30,000. On the other end of the spectrum I have also seen posts of MLs in the 100,000 + miles and still going strong. To get this many miles in a few years likely means highway miles, which are probably easier on the vehicle.

I also recall seeing somthing about the specs on the transmissions were different for the ML 320 vs. the ML 500.