Just for information, one of the first MBs to utilize the 5spd A/T was in 1992 in the 300SE. The final drive ratio of that car was a
3.69 just to get that mass of nearly 4800lbs moving, but once moving it would cruise effortlessly and got good gas mileage. And that is with tires larger than yours probably as they were 225/60-16s. A 2.82 would be fine with the 4 spd A/T without the overdrive high gear but with the 5 spd with an o/d fifth it seems it would like something lower like a 3.27.

Tobias MB
4 MBs