What gears would you choose?

Discussion in 'Drivetrain' started by Witzy0070, Feb 3, 2016.

  1. Witzy0070

    Witzy0070 Active Member

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    So here's where I am at with the Cobra. I had 3.73s in the back with about 400RWHP which was a tad lacking. So I installed some 4.30 gears in the back (1996 Cobra 4V). Was all fun and games until we added more boost, methanol, and a 100 shot of nitrous. Now I have no gear to run at all, it's over almost faster than I can shift with a shot of nitrous and almost 200 more RWHP. I want to be able to run the nitrous and other new mods more effectively, but I don't want to bog down. I've got a set of 3.55s and 3.73s in my garage, what do you recommend to get the most utilization of power?

    PS Nitrous gets you in the powerband fast.
     
  2. Rob04Mach1

    Rob04Mach1 New Member

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    I found 4.1's to much with my 99 Procharged GT with a T45. Ran 3.7's in my 717 RWHP Terminator but that was a reverse manual 4 speed auto with a brake and the perfect gear for me on the street. Had the stock 3.2's in my 96 Cobra with T45 and man was that sluggish. Got 3.5's in my current Procharged Mach 1 and I feel it's the perfect gear for my set up (All Alum 4.6 DOHC with a D1 Supercharger and a 4r70W Level 10 Trans & Converter). I would say go with the 3.7's
     
  3. Witzy0070

    Witzy0070 Active Member

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    Gotcha, well I am leaning more towards the 3.55s because I don't want to not take enough out. I have 285-35-18 tires through a T-45.

    Man I just am not sure.

    Thank you for your input.
     
  4. 96blak54

    96blak54 Legend

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    Oh yea! 3.55's mid 3rd gear pull will feel awesome!
     
  5. Sinned83

    Sinned83 Well-Known Member

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    3.55's is the best gear with power adders IMO
     
  6. evilcw311

    evilcw311 Most Evil Mod! Staff Member Staff

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    3.55 is what's goin in mine but my car is turbo.

    Friends I have that live around me with blowers both have 3.55 and love it.


    This message courtesy of crapatalk!
     
  7. Witzy0070

    Witzy0070 Active Member

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    Ok, thanks for the replies so far, any of you running the high revving 4.6?
     
  8. Sinned83

    Sinned83 Well-Known Member

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    I got 4.10's in the Mach
     
  9. Witzy0070

    Witzy0070 Active Member

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    Auto or stick, what size wheels, are you running a blower/meth/nitrous? Thanks.
     
  10. Sinned83

    Sinned83 Well-Known Member

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    5 speed, I got 18's and No boost or nitrous
     
  11. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    The real answer to your question, I think, is what does your power band look like? The whole point of gears is to adapt the car to the available power band, such that you make the most out of it. I apologize in advance if this obvious to everyone. Depending on where your power band starts and tops out, you could run, for example, 2.37's and that would be perfectly fine (read: fast). I'm not suggesting you do this, I am merely trying to point out that the gear selection has a lot of variables. Do you drag race? Do you care about top end speed? Without going into the reasons (I will be happy to if you would like), I would think 3.55's would be good - you have tons of power. Granted I am not super familiar with the 96 Cobra's, so there's my disclaimer. But at your original WHP, you were putting about 5000 WTQ (give or take) to the ground in 1st gear. Granted, not for very long, but I'm not sure how you didn't boil your tires (unless the Cobra is really heavy or something?). Even with 3.55's, you will be putting about 4300 WTQ down (give or take). That's still quite a lot. If you have a problem with tire slip from a start, go with higher gears. If you are gripping like a sumabeech with no tire slip, keep your current lower gears. Personally, I think 4.1 (and maybe even 3.73) is too much gear, but again I have no experience with this car. And also the rest of the internet says stuff like "4.1, 4.56, don't fear the gear, blah blah." I don't know. In the end, you are making the same power either way. Your car will be fast either way. Drag racers use gear to minimize shifts before the 1/4 mile marker. You drive your car in the real world. I would think having to shift all the time would be annoying. (Unless you drag race it?)

    Another way to think about it: 4.1's mean you won't hit 60 mph in 2nd gear, it will require you shifting to 3rd. 3.73's will let you get to 60 (and just a bit past) in 2nd gear. Which do think is faster? The car that has the extra shift, or the one that doesn't? (Hint: usually it's the one that doesn't. Ask me how I know.)

    Remember, the Torque you get from lower gears isn't free - it means the engine has to spin more. Which means you don't get as many revolutions of the tire in that particular gear. Which means you don't go quite as far (which is also why your mph is lower). Now, you have more Torque to help you go, but you still move through the rpm's very fast. If your car has a nice flat power band that's decently wide, then you would be better off with lower gears to take advantage of the average power your engine produces. If your car is peaky and has a very narrow power band, especially up top, then you are better off with higher gears to help you get there quicker. Also, the butt dyno will tell you that lower gear is faster because you feel the g's more. But keep in mind your butt dyno can be deceived. Just because a car feels faster doesn't mean it actually is.

    Lastly, a good analogy is this: lower gears (4.1) are like sprinters. Quick of the line, but die very soon. Higher gears (3.27) are like endurance runners. Not the fastest in a sprint but will go a lot longer. "Middle of the road" gears (3.55) are just that. They are a compromise. One could argue they are good at neither, or one could argue that they exhibit some of the better qualities of the two without the extreme downsides. Ultimately, it's up to you and how you want your car to drive. If you felt 4.1 was too much, try 3.55. If that's not enough, then it looks like 3.73's are the ticket ;)

    Edit: I forgot to add: if your goal is to get the fastest possible car and don't care about redline or top end speed, go with the lowest gear you can stand (and that will grip).
     
  12. evilcw311

    evilcw311 Most Evil Mod! Staff Member Staff

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    ^that about sums it up!!!! Lol


    This message courtesy of crapatalk!
     
  13. Witzy0070

    Witzy0070 Active Member

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    I am not good at responding to a lot of points so forgive me if my break down is tedious due to the large amount of good information in this post.

    My power band is different than the SOHC and OHV engines, the car doesn't really come alive until about 4k to 6k RPM. My build makes power until 6900 RPM but I don't like how the shift light melts my retinas after 6500 and I enjoy engine longevity.

    I don't bring the car to the strip, that's for my Neon. lol. The Cobra is a street warrior. I've done over 150 in the Cobra, that was fun, don't need to experience that again, so top end isn't a big deal. My torque is near 400 ft lbs, with nitrous not dynoed but significantly higher. I have good tires, torque bar, welded subframe, coilovers, and a Torsen diff, so traction is pretty good. Granted with my 4.30 gears now 1st gear is truly useless and 2nd gear lasts about as long as a virgin.

    As for your analogy I have been pulled on cars with less horsepower/etc just due to having to shift so frequently.

    And finally for your last line that was my school of thought, however I was talking to a friend of mine who used to run an old Camaro that ran a 9.7, when he built it originally he made the engine set up for nitrous on a 250 shot. He ran a 4.11 ish gear at first (can't remember the exact ratio) and ran a 10.5, when he swapped to a higher gear a 3.55 (again an estimate) he lowered his time to the 9.7 with the nitrous shot. From what I've read and heard nitrous likes a steeper ratio such as a 3.55 as opposed to a 4.30, can anyone confirm this?

    Plus the 3.55s would make the freeway not so bad again... Anyway, thanks for the help, I really do appreciate it! I'd buy you a beer.
     
  14. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    No sweat dude, it's my pleasure, glad it ended up being helpful! :D

    Even with your power band where it is higher in the RPMs, I think you'd still benefit from taller gears like 3.55's. I'm assuming you have a really good amount of torque down low, and with you in the car it probably weighs around 3500 lbs or so. I can't imagine you'd need help from lower gears to get you going, I think you have plenty of torque. If you are driving a Honda S2000, for example, then it's a different story.

    It's the difference between a peaky car vs a broad car. If you have a broad power curve (larger displacement engines, FI adders, tend to be broader curves due to the nature of the engine/FI) then you want to spend more time in the RPMS there because you will be putting down, overall, more average power. Peaky cars (Civics, S2000's, RX-8's) tend to have dickall for down low torque, thus the lower final drive gear to get them moving. Neither is better or worse, just different characteristics for different cars. Since nitrous (and FI) is essentially amplifying the available power over the broad band, you should use a gear that stays in that band longer. Your car will end up being faster.

    Another example: trucks, like 18-wheelers. They have a very small power band. Like 1800 to 2000 RPM (I don't know exactly). After like 2000 RPM, the party is over. They make literally metric asstons of torque, but hardly any HP. Because the band is so small (peaky), they all have like 20 gears so the driver can keep the engine in the power band. And I'm willing to bet that their 1st gear ratio/final drive is something astronomical. But then again, they are super heavy so that's what they need.

    Edit: oh and the hint from the previous post, when I was looking at buying a WRX vs. STI, one of things I saw a lot was that the WRX was actually just a tad quicker 0-60 than the STI. Which is a head-scratcher initially as the STI has more HP and TQ (and they weigh about the same). The reason: WRX was a 5 speed, STI 6 speed. The WRX had one less shift 0-60. Which car is faster though? Obviously the STI - unless one lives their life driving 0-60 at a time. Then I guess the WRX is for those folks.
     
  15. Thomas_W

    Thomas_W Well-Known Member

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    Based on what your saying, i'd go with 3.55's

    I had a 96 supercharged 4.6 2v with 4.10's, it was a blast to drive but first gear was worthless. When I went turbo, i dropped to 3.55's and doubled the HP of that car. First gear when the boost hit was amazing tire spin (315 series 17's in the back) when it hit 3500 (and 21psi), but the tire spin continued all the way into third gear. You could go into 3rd gear on the interstate from a roll and get it to spin the tires. Absolute blast of a car. But, it was just as fun around town out of the boost. It wasn't gutless like the stock 2.73 gears, but it gave you enough pedal room to still be able to get a good enough amount of street hook to piss off the old man in the Vette. lol This was with a T45 btw.

    3.55's are IMO the best gear for any Forced Induction power adder. For straight nitrous, 4.10's are perfect for 1/8 mile cars, 1/4 mile i'd go with 3.73's.
     
  16. Witzy0070

    Witzy0070 Active Member

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    Thanks guys, based on your input I am going with 3.55s. Dropped her off a few hours ago. Can't wait to get her back and run a 125 shot!
     
  17. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Let us know how it turns out!
     
  18. RichV

    RichV Well-Known Member

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    I know I'm late to the party, but here's my 2 cents.

    I had 3:73 gears in the road racer for a couple of seasons. Stock 94 T5 gearing, GT40 top end with a E303, about 260rwhp. On track, didn't matter which one, I was shifting a lot. Plus the stupid OD 5th was like dropping a boat anchor when I shifted into it, which was roughly above 100mph. So I did the calculations and went with 3:27, it's night and day. The car is faster at any track, less shifting, and I have essentially a usable 4 speed rather than a unusable 5 speed.

    So if you need the launch or don't have power, higher gears are great. But you have plenty of power and could go with much less gear. The 3:55 won't be drastically different than the 3:73. I had a 86 Saleen with a HCI procharged 5.0, I could spin drag radials with a downshift to 3rd gear at 60mph, it only had 3:08 but man the pull on the highway was awesome.
     
  19. 96blak54

    96blak54 Legend

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    Im running 2.73's. The 3rd gear feels awesome with 350tq to an engine that runs out of breath at 4krpm. Come to think of it.... Ive never been out of 3rd gear when hammering on it. Probably cause it could do 150mph...lol! 2nd gear tops almost 90mph....this is to funny!