Ok, so I allready have the gears sitting here. They will go in a 97 bolt on car with an FLP Stage 4 and 2800 converter. Car currently has 3.42's. How much MPG am I gonna lose, and is there going to be a huge/noticeable difference going from 3.23 to 3.73? The car is my DD, mostly in town driving with about a 150 mile round trip drive about once a mont.

 

You'll notice the upgrade. MPG wise it should lose i'm guessing around 1-2 depending on how heavy your foot is.

 

Ok so does the car have 3.42's or 3.23's? You said both. If it has 3.42's, I wouldn't swap em. The difference or improvement you may see if at all will be so minimal, it won't be worth it. If it has 3.23's I say go for it. You will definately see a nice improvement. Gas mileage(aside from higher speed highway travel) will probably only suffer because your right foot will become heavier from the fun. The car actually works easier to get itself moving when around town, so as long as you stay off the throttle you'll be just fine. And highway gas mileage isn't really that bad as long as you stay around or under the 70-75mph range. Any more and you'll just watch the gas gauge move.

 

What he said. I am currently waiting for my 3.42 rearend to have problems so I can upragade to axels and go to 4.10s......I wouldnt even think o0f 3.73s not worth the money for the change. Gas mileage wont change much at all if you dont push it all the time.......I try to stay in 5th at 30 MPH

 

dadgummit, The car has 3.23's, got confused with my '94 i suppose.