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

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


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68Dart500

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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.
 
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.
 
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.
 
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.
 
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
 
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.

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.
 
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.
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.
 
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 *** 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.
 
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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.
 
What RPM would people suggest launching at with that combo?

Just as high as you are willing to go that will still allow the rear tires to hook. ;-)
 
Stock flywheel, I would not trust that.
I would spend money on a quality SFI one before gears.
 
Stock flywheel, I would not trust that.

I would spend money on a quality SFI one before gears.

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.
 
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.
I run that one also and love it.
 
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.
 
Use a 27" tall tire (275 60 15) and a 4.30 gear. You'll never look back.
 
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 !
 
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.
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
 
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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


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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