rear end

[craig akiyama]

here is my question, chevy rear end corpret 10 bolt 8.5 inch 2.73 ratio 41-15 teeth, want to go lower, BUT not to low to not be able to take some freeway trips, looking in jeg,s cat. 3.73 or 4.10 seem middle of the road.not somthing i do, really never did, so I could use some advice here THANK YOU.

[rspears]

Craig,
To get where you want to be you need to look at your final drive ratio in your tranny (OD ratio if you have OD) and your tire diameter in inches. A simple formula, using a "unit coordinator" number of 336 is Cruise RPM = (mph x Gear Ratio x 336 x OD Ratio)/Tire Diameter. Miles per hour, OD ratio 2.73, no OD (1.0 ratio) and rear tire diameter of say 29" would say that at 70mph you're cranking 2214RPM. Ideally you need to look at the torque curve for your engine, and ensure that you're cruising at a RPM that is at or near the point where your torque is coming up on the flat portion of the curve. That will ensure that you have some "punch" if you're loping along at 70mph and need to jump out to pass or get out of the way.