What gear ratio for a street car w/occasional track use?

Transmission and Drivetrain Tech

What Gear Ratio for Street with 3-4 time a year track use?

  1. 3.55- Keep what you have

    44.3%
  2. 3.73

    20.0%
  3. 3.91

    18.6%
  4. 4.10

    17.1%
  1. 68Dart500

    68Dart500 Well-Known Member

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    I've decided that I think I want to swap out my 3.55 gears in my 68 Dart 408 stroker. It's a 4 speed manual with the 2.44 (I believe that's what it was?) 1st gear. After this last tuning session its making roughly 500 hp and 540 ft/lbs torque. I'm running a 28x12.5-15 Bias ply wrinkle wall tire.

    I'm just not as happy with the 3.55's as I thought I would be. Thinking I should have gone 3.73 or 3.91's.

    It will spend 95% of its time on the street with spirited stoplight to stoplight driving and some highway to get to shows within a half hour or so. Probably 3-4 times a summer I'll take it to the track. Am I crazy wanting to change the gearing being its not a track car?

    Currently it cruises at about 3000 rpm at 70.
     
  2. Mopar Tim

    Mopar Tim FABO Gold Member FABO Gold Member

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    I swapped the gears in my 408 Dart to 3:23 from 3:55. It is not as quick out of the hole, but a 408 has tons of torque, so it recover quickly and is lots more fun to drive on the freeways of So Cal.
     
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    • 451Cuda

      451Cuda Well-Known Member

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      I like 3.91 for a street/strip 440, probably the same results for your 408.
       
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      • mbaird

        mbaird mbaird FABO Gold Member

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        since you mentioned the rpms at 70 I have to assume you have occasion to use it on the highway. You might grow tired of the 3.91s in short order. 3.55s are a sweet gear for Torque monster motors.
         
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        • mderoy340

          mderoy340 Well-Known Member

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          You have the data of highway rpm now, what can you live with? Go drive the highway in 3rd gear and do math to calc current final drive with the 3.55. More gear will drop et if your car hooks. I run a 3.91 but got lucky and picked up a used GVOD. Driving 50 miles to the track gets old and the GV knocked off 400 rpm at cruise.
          Are you disappointed in track performance? More to good et than horsepower. Post up your combo, more ways to get a car quicker than just gears. Do you have a baseline time slip you can post.
           
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          • Alaskan_TA

            Alaskan_TA Well-Known Member

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            The center sections are easy to swap in & out, so buy a second set in your ratio of choice & install it for your race season.

            3.55s with 15" tires is optimal for street use to me.

            With lots of highway, I like a 3.23
             
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            • 68Dart500

              68Dart500 Well-Known Member

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              You're right, the highway driving is good right now so maybe I just live with it. I could always get a 2nd set of rims/tires with some 26 or 27's for the track. Just run the 28's on the street.

              I am actually going to be racing (for fun) at the Mopar Nationals for the first time with this combo in 2 weeks so that I've got a baseline. Currently I'm running new XHD Mopar leaf springs, adjustable pinion snubber, springs moved into frame and mini tubbed with custom 15x10 steel dog dish rims with 28x12.5-15 Mickey Thompson Sportsman Pro Bias ply tires. 23 Spline 4 speed with a centerforce dual friction clutch. Chromoly driveshaft w/1350 joints. 489 case w/crush sleeve eliminator, 3.55 Yukon Gears, Auburn Pro LSD, Moser Axles. Subframe connectors and a full interior with all steel body. Also has a Quicktime bellhousing, steel stock flywheel, and driveshaft loop also so I'm sure its fairly heavy.

              Speaking of track performance. What RPM would people suggest launching at with that combo? Obviously this is a for fun car so I'm not looking to blow stuff up with a 6k rpm launch. On the street it seems to spin minimally if I only rev to 3k rpm. But 3500 or 4k it will spin for 20-30 feet. I realize the track will be much stickier so I'm just trying to not have it bog but also not break stuff.
               
            • mderoy340

              mderoy340 Well-Known Member

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              I could always get a 2nd set of rims/tires with some 26 or 27's for the track.
              IMO this is the way to go. 26" Launch rpm is test at several rpms. Get up and stage the car and don't worry about RT. Make sure you are at 1500, 2000, etc and see what is best.
               
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              • MOPAROFFICIAL

                MOPAROFFICIAL Well-Known Member

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                For me...3.55 gears just don't have it for the strip... And 391 gears ,though still mild, are too much for the highway for most people.

                Imo 3.73's are it when it comes to a REAL dual purpose car with a 1+1 final drive.

                I ran a 340 with 3.23, 3.55, 3.91, 3.73 and out of all of them the 3.73 was the most versatile gear. 3.91 hauled ass 3.55 was slouchy in the midrange and low. 3.23 was a dog...till you got to 70 mph.

                Doesnt seem like much diff between the 3.55 & 3.73... but there is.
                 
                Last edited: Jul 27, 2018
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                • yellow rose

                  yellow rose Doctor of Thinkology.

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                  You didn't have an option for 4.56 gears.

                  That's what I'd use.
                   
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                  • mbaird

                    mbaird mbaird FABO Gold Member

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                    Well hell... you have enough in driveline components to support a wheelstander !

                    launch it at 6k...lol

                    But really your rpms will be dictated by your engine build / gears and chassis setup.
                     
                  • Alaskan_TA

                    Alaskan_TA Well-Known Member

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                    Just as high as you are willing to go that will still allow the rear tires to hook. ;-)
                     
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                    • sireland67

                      sireland67 Well-Known Member

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                      Stock flywheel, I would not trust that.
                      I would spend money on a quality SFI one before gears.
                       
                    • mbaird

                      mbaird mbaird FABO Gold Member

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                      That occured to me as well ...

                      I am using a 20 lb Mcleod SFI flywheel for my stroker... a little less weight (10 lbs) for quick revving and peace of mind for around 299.00

                      with all the trick driveline stuff you have it seems ashame to run a factory iron unit.
                       
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                      • abodyjoe

                        abodyjoe Well-Known Member

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                        Shit 95% street I’d go to a 3.23. :)
                         
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                        • Abodybomber

                          Abodybomber Breaking street machines , since 1983.....:) Legendary Member

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                          Rear and front suspension setup?....
                           
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                          • cpearce

                            cpearce Well-Known Member

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                            I run that one also and love it.
                             
                          • mbaird

                            mbaird mbaird FABO Gold Member

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                            my car is still in build mode. how does that fly wheel feel on street ? quick revving but doesnt stall out from stoplights I hope ....
                             
                          • 68Dart500

                            68Dart500 Well-Known Member

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                            I went with the quicktime explosion proof bellhousing so I was protected from a clutch explosion too. If it's a good idea I'll get the flywheel too I guess. What causes a flywheel to blow typically?

                            I think I'll start off with a 2500 launch at the track. Then go up 500 rpm at a time.
                             
                          • RustyRatRod

                            RustyRatRod Weenie idiot loser. FABO Gold Member

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                            Use a 27" tall tire (275 60 15) and a 4.30 gear. You'll never look back.
                             
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                            • fishmens67

                              fishmens67 Well-Known Member

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                              Street? Strip? 4.10 a true grocery getter with a 26" tire. 4.56 if ya can get 28" under it.
                              My car hasn't seen the highway in decades. it's idling along or full 1/8 or 1/4 mile blasts.
                              I prefer our Taurus for all highway driving. comfy !
                               
                            • 68383GTS

                              68383GTS Well-Known Member

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                              I have a 489 410 with a locker that I would trade for a 355 suregrip or locker....
                               
                            • mopardude318

                              mopardude318 Well-Known Member

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                              I'd say 3.73 gears!
                               
                            • AJ/FormS

                              AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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                              With what 28" street tires? I want those!!
                              If I had a 408, and that's all it would do with a starter gear of 3.55x2.44= 8.66, on street tires, I'd be disappointed too.

                              That 2.44 only came in the Hemi-boX. If you have a 1x23 input then you have either a 2.66low, or the waaaay less common 2.47low, T/A box. There was a third box, in the first-gen Barracudas with a 3.09 low. You shouldn't be needing that one,lol.
                              The 2.66 box has a 9% better low gear and slightly wider ratios than the 2.47.. And the 3.09 box has a 16% better low gear than he 2.66, and the rest are the same. Here are the ratios;
                              2.47-1.77-1.34-1.00 and splits of .72-.76-.75 Close ratio 70 T/A
                              2.66-1.91-1.39-1.00 and splits of .72-.73-.72 Common
                              3.09-1.92-1.40-1.00 and splits of .62-.73-.71 1st-gen Barracuda deep-low
                               
                              Last edited: Jul 28, 2018
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                              • yellow rose

                                yellow rose Doctor of Thinkology.

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                                I thought after 1970 all 4 speeds were the 2.47 low gear? My 72 Demon was a 2.47 low, interlocking lever side cover box.
                                 
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