Gear choice

[Cottonmouth45]

Hello, I am new to this group, this question is probably been asked 1000 times so I’m gonna ask it one more. I have a 1968 dart with a solid 318 four barrel. I have a A – 833OD transmission and currently I have 2.72 gears in the rear end. I wish to change the gears to make this car a lot more fun to drive. I do not care about gas mileage, and I do not care that much about long-distance driving. The most this car would ever see on the freeway is maybe an hour. I really just want a car that is fun to drive from stoplight to stoplight. I was thinking something along the lines of 3.73 gears that after reading a few articles, I’m thinking that might to much.

 

[Icetech]

I believe the OD ratio on that trans is .67.... i personally would go 3.91 or 4.10s... Can always use a RPM calculator to figure out your driving rpms.. I run 4.30s without a OD right now.

Spicer Engine RPM Calculator

Measure your engine’s RPM based on the ring gear and pinion gear ratio, speed, and tire height, with the Spicer Engine RPM Calculator.

spicerparts.com

 

[MMissile]

When in doubt, I always went with a 3.55 Tire height changes the final ratio, also.

 

[Cottonmouth45]

When in doubt, I always went with a 3.55 Tire height changes the final ratio, also.

215/70 14

 

[Icetech]

215/70 14

3.23 or 3.55.. you are going to have zero traction no matter what..

 

[Cottonmouth45]

I believe the OD ratio on that trans is .67.... i personally would go 3.91 or 4.10s... Can always use a RPM calculator to figure out your driving rpms.. I run 4.30s without a OD right now.

http://[URL][URL]https://spicerparts.com/calculators/engine-rpm-calculator

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Just want to have a good time with out redlining it at normal driving around town.

 

[Cottonmouth45]

3.23 or 3.55.. you are going to have zero traction no matter what..

I figured that. Can’t get a wider tire in there unless a get some custom rims made. The rear end is out of a 1976 Aspen station wagon and it was about a half an inch wider than the 7 1/4. I took out. There’s just enough room for those tires in there without scraping on the fender well. I can’t even get one finger in between the tire and the fender well

 

[Icetech]

The size wouldn't be too bad if you can find sticky tires, not sure if they make anything for 14s though.. Car would be great at burnouts

 

[mbaird]

3.55s… 3.91s might prove too deep with the 3.09 1st .
Personally while I like the OD if you don’t care about mileage or hiway driving I would swap to a normal 833 and run 3.91s .

 

[Cottonmouth45]

The size wouldn't be too bad if you can find sticky tires, not sure if they make anything for 14s though.. Car would be great at burnouts

I can not do a burn out to save my life right now. It’s like driving a tractor. I rarely use 3rd gear let alone the overdrive.

 

[Cottonmouth45]

3.55s… 3.91s might prove too deep with the 3.09 1st .
Personally while I like the OD if you don’t care about mileage or hiway driving I would swap to a normal 833 and run 3.91s .

I was gonna run 3.73 but started thinking that was too much.

 

[Darter6]

For me it's 3.73. We did several cars with O.D.'s Best of both worlds.

 

[Icetech]

I can not do a burn out to save my life right now. It’s like driving a tractor. I rarely use 3rd gear let alone the overdrive.

Yeah.. the 2.72 is great if you are on the highway all day

Go 3.73 and be happy... you can always get some 15" rims and stickier tires if you need to. Or cut the wheel opens and make a fake hemi dart

 

[moparlvr166]

Go with 3.91 and you can drive on freeway in 3rd gear and still accelerate if needed, if you used 4th for OD you would be just below your 2.72 for gas mileage if you want to take a longer road trip.

 

[Ottmundr]

You are locked in with your transmission and the OD helps.
You are kinda locked in with your exhaust, heads, compression ratio and cam.
You are less locked in with carb and intake manifold.

Build everything based off the cam. You pick your cam based on the performance you want from the engine. That is the computer program that determines everything else.

If you're unwilling to change your cam, then you need to figure out your torque curve and build your gearing around that and how well the heads feed in the air and fuel... You can't complain when you don't get what you really want.

Go on Amazon and look for the Automotive Engine Math book. I'm a retard and i am grateful that book exists.