I think the axle ratio is 3.46:1.

The problem you have is a nearly 4000 pound car with a 3L engine that produces about 175 lb-ft of torque at 4000 RPM.

If you regear, it will probably be a slug, even with first gear starts, and the cost would be very high relative to the value of the car.

You're better off just driving it into the ground or selling it and getting a V-8 S-class.

Most of the M103 engine cars with automatics are turning 3000 or more revs at 70 except for the later 300Es with 2.87:1 axles.

The manual transmission versions are much more relaxed with their overdrive fifth gear.

Duke