I am driving Grand Cherokee 3.0 CRD and it has Mercedes W5A800 transmission. The engine is Mercedes' new and lovely 3.0 diesel unit which has 218 hp. I feel that the car can go more than its top speed (125 mph) but because of the ratios I reach the kill. Did anybody try to change the 5th gear ratio (somewhere between 0,68-0,72)? I want to beat BMW X5's with my diesel

 

Have you considered changing the differential ratios instead, which would be considerably easier?

Charles