Best Gears For The Track?

Discussion in '1996 - 2004 SN95 Mustang -General/Talk-' started by Nightfire, Apr 11, 2014.

  1. I currently have 4.10's with a stalled 4R70W auto and 500rwhp. The 4.10's are no bueno at the track, Im running out of gear. My builder has both 3.55's and 3.73's that he'll trade me for the 4.10's.

    So, 3.55 or 3.73? Im leaning towards 3.55
  2. 1. How fast are you going to be trapping?
    2. What is the most RPM you want to turn?
    3. What size tire?
    4. Do you want room to go any faster?

    I'll wait till I hear those answers to say for sure, but I'm gonna give a preliminary suggestion of 3.73s. If I remember correctly from some math I did a few days ago, 3.73s, 6500 rpm, and a 26" tire will get you over 133 mph, which I doubt you'll even be close to.
  3. 1. I would guess 120-125ish
    2. Unknown (stock cams)
    3. Stock size (26?)
    4. Absolutely, but would change gears again if need be.

    Im looking for the best gear for my setup as it sits now. If your math is correct, 3.73's would be the best option.
  4. When I had PI cams, the ideal shift point was still way up there (6500+). So the limits of your shift point will likely just be your valvetrain limits and where you feel comfortable running it to. I suspect it'd be fine to up close to 6500 on all stock stuff.

    With stock size tires (25.66") and 3.73s, 120 mph would be 5863 rpm. 125 mph would be 6107 rpm. 130 mph would be 6352 rpm. So as long as you are ok with turning 6300-6400 rpm, and don't plan to go over 130 mph, the 3.73s are certainly ideal for the track. 3.90s might actually be more close to perfect if you're only going 120ish, but I personally wouldn't run a non-Ford gear, and you wouldn't have as much room to grow at that point (6500 rpm would only be 127 mph). And even if you did move up into the 130 range, it's probably be good to start looking into a taller tire anyway.
  5. I have upgraded springs/valves/guides/lifters/everything so my valvetrain will handle pretty much anything. The gears will be the limiting factor. 3.73's sound right for now.
  6. I think I would choose the 3.73's as well. It's easier to step down if needed and know you need the 3.55's vs going with 3.55's and wondering what if with the 3.73's.
  7. I would go 3.73 given what your potential trap speeds would be, and as said before you can always start looking into running the taller tire down the road. 3.55 just isn't enough on the big end, and 4.10 would be reserved for those spinning north of 7k RPM near the finish line.