Im pretty sure I have a 7 1/4 in my car, but how can I figure out what gear it is (probably 2.76s) and wether its a sure grip or not? How can I be sure if its a 7 1/4 or an 8 1/4? Whats better 2.76s or 3.23s, sure grip or no sure grip?

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'74 Duster 225 Super Six w/904
14" Cragar SS wheels

I will have a round cover and 10 bolts around the edge... if you have a 7 1/4".. it will have 9 bolts in the cover and be an odd shaped cover...

Make sure you crawl under and count... the 7 1/4" have 5 bolts on the bottom half of the cover and 4 on the top half...


-D.Idiot

Look here:

http://www.crankshaftcoalition.com/wiki ... er's_Guide

Jack up one rear wheel, transmission in neutral, wheels chocked, try to turn rear wheel by hand. If it turns with the other wheel on the ground you do not have sure grip. If the wheel dose not turn you have sure grip, jack up the other wheel so both are off the ground.

To determine rear end ratio, slowly rotate rear wheel two full turns (use valve stem as a reference point at six o'clock) while at the same time counting the quarter turns of the drive shaft by looking at the rear U joint. I count as the baring cap passes the floor, this way you can count a fractional quarter turn

Divide the number of quarter turns by 8 to get the ratio.

Example:

28 quarter turns divided 8= 3.5, so this sugars out to 3.55:1 or 3.54:1

23.5 turns / 8= 2.93 or 2.93:1

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Its a 7 1/4 then. I will have to determine the ratio and sure grip or not tomm. Thanks for the info guys!

Another question, what are the best gears for a car? Gas milage wise and performance wise?

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'74 Duster 225 Super Six w/904
14" Cragar SS wheels

In general numerically lower gear are better for fuel economy and higher numbered gears give better torque to the ground. Aside from that there is no easy answer to your question. It all depends on how your car is equipped and how you intend to drive it.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

to go fast to 60 higher numbers 3.55, 4.11 etc. For economy 2.91 , 2.76 etc.low numbers. Picking the right ratio for the right job.

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63 valiant v200 Wagon 9.5, Schneider cam, E.I. 22 mpg all day

It's a compromise, with lots of factors to consider.

I'm happy with a 2.94 gearset in a 7 1/4", with a near stock engine, pushbutton 904, and 205/60R15's. Daily in-town driver with occasional long highway trips.

Numerically higher gearing would be more fun off the line. A lower ratio like 2.76 might help highway fuel economy, but ... I'd rather stay close to 3 or a little over.

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

Its not a sure grip. Oh well... Im gonna have to find the gear out later, but im pretty sure its probably 2.76s What cars had the sure grip? I want one with probably 3.23s, but any sure grip would be an improvement. Could I just get another set of gears?

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'74 Duster 225 Super Six w/904
14" Cragar SS wheels

No on changing gears to get a suregrip. 3.23 was mostly found on stick shift cars. Some cop cars ,taxis,etc got suregrips.
Frank

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

How could I change my gears to a sure grip? Can I just buy a set and change them out?

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'74 Duster 225 Super Six w/904
14" Cragar SS wheels

You would have to buy a suregrip unit and gears. For a 7 1/4, they are rare and can get expensive. Might be better off getting an 8 1/4 with what you want in it or what i'm putting in my Valiant: 8 3/4 3.55 ratio Suregrip, can't wait!!! You can buy these items on the net or go search a junkyard for this stuff. Someone will probably chime in on what cars you can look for to pull off of....

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-1972 Valiant-

'72 Valiant

Get an 8 1/4 off of a 90s Dakota ( check for ratio and SGrip) have it narrowed and drive on.
Frank
PS Carparts.com is your friend

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

On the Dakota; stay between the years 87-90; 91+ had 6 lugs. A Cherokee (Not Grand) is another good swap candidate. Be sure you get the 8-1/4 and NOT the Dana 30/35 version. They put both in the Cherokees,

What about the SBP? Do the Dakota rears have the SBP? And about having it narrowed, how can that be done, and how much would that cost?

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'74 Duster 225 Super Six w/904
14" Cragar SS wheels

in A body talk a 87-90 will be BBP (big bolt pattern-5 on 4-1/2) as will the Cherokee;