ok so i have a 66 fury that had a 318 poly in it i took it out and put in a 383 with a 727 every works fine the 383 is stock other then a edelbrock performer rpm intake manifold hedman headers a new dual exhaust and a edelbrock 650 carb .............my rear end is a 8 3/4 and the gears are killing my car it has no get up and go to it what gears do you recomend for it ???? it will be drived often but not a daily driver and i want it to get up and go a bit .....i was thinking 3.55 gears but you guys tell me what you think ...thanks

 

You need to determine where you want the engine RPM at cruise, whatever speed that might be. In some parts of the country, that might be close to 80, and in some parts, and depending on your driving, might be closer to 60/65

Then either figure from your rear tire diameter, or whatever diameter you think you want to and eventually put on the car for rear tires.

(Google your tire size, or Google "tire size chart, etc)

Then figure what you have for a ratio now in the axle, and go from there.

Block the front wheels, jack up only ONE rear wheel and put the trans in neutral. See if you can turn the wheel. If so, you do not have a Suregrip (limited slip) axle.

So use the filler stem for a reference, and while counting driveshaft revolutions, turn the tire TWO full turns exactly. The shaft will turn the amount of the ratio, IE a 3.23 axle, the driveshaft will turn 3 1/4 turns, 3.55, just over 3 1/2 turns

Now if you can NOT turn the wheel, make absolutely sure the parking brake is off, and the trans in neutral. If you cannot turn the wheel, you have a SureGrip axle, and now you'll have to jack up BOTH rear tires.

This time, turn one of the tires only ONE turn, and count shaft turns. ONE turn of either wheel (they should turn together) will result in the same shaft count as described earlier.

Then just Google up one of hundreds of mph/ gear calculators and "calc" away.

 

i know i dont have sure grip and my gears are very low they are like 2. something i just need help picking gears for it i would also like to change it to suregrip as well i just dont know what gears use

 

You probably have a 2.91 a 3.55 is a good choice between a performance & street
gear.

 

The 3.91 truck with overdrive auto trans was nice, now with the three speed no overdrive always feels like it needs one more gear. My 3.23 car with 3000 stall always felt like it needed something more out of the hole but sure pulled nice from 60-100mph. We are changing the truck to a 3.55 to keep some low end umph for towing.

I agree the 3.55 is a great all around street performance gear. If you do your speed calculation, a 2" tire size change can make quite a difference.

 

A 383 should have plenty of "get up and go" in it regardless of the gearing unless it's some weird combo with 2.76 and big tires. Exactly what do you mean by no get up and go?

I think 3.23 is the best compromise for a streetable C-bod car running stock sized tires. The older ones like your 66 are the lightest, so you should not be having this issue.