3.54 Final Drive Swap Review

track370

hey KusoSama,

what do you mean "less work to do more gearing"?

Changing final drive won't change your engine HP or Torque numbers, it only has an effect on what is after the final drive and that is what is important to most people or drivers because that is what you feel. Final drive has an enormous effect on wheel horsepower and acceleration ("pull"), not sure if your comment was referring to the former or latter.

By going from a 3.69 to a 3.54 drive you have simply just decreased your wheel torque by about 4% across your entire powerband. Since horsepower is simply a function of engine rpm and torque, you have decreased that as well. In terms of pull, as you mentioned, it is torque that is doing the work to accelerate you, so since you have decreased that, with all other variables aside you will accelerate or "pull" 4% slower than a car with 3.69 gears at a given rpm (as long as you are not in a powerband where you are traction limited, because then you will obviously be accelerating at the same rate which is limited by your tire). However with that effect you gain longer gear ratios and higher top speed.

It all depends on personal preference, if you don't mind losing acceleration for having to shift less then you did the right thing. Or like you said if you plan on doing FI and boosting to a point where the amount of added torque makes daily driving difficult or increases torque beyond your traction limit, then you went the right way. However, if you want more acceleration and can afford to, then you would want to go the opposite way. Its all personal preference which may be greatly effected by what you use the car for (DD, track, drag, etc).

I personally would go the other way if anything, not being traction limited for the majority of 2nd gear, I would appreciate a bit more acceleration at the sacrifice of shifting slightly sooner Especially because that additional torque will be apparent in every gear after that also, and I won't be doing any performance mods that will significantly increase my torque curve. But then again I DD my z so i wouldn't go drastically higher due to the effect on fuel economy, shifting, etc.

-Matt