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I am about to change my gear ratio and I figure while I'm in there, perhaps its time to change to a locking differential. What effect, if any, will be noticed?

My car is a '66 coupe that has a recently rebuilt 289 motor (heads surfaced, valves ported, 1.6 exhaust, 1.94 intake, roller rockers, cylinders bored .03, 3/4 race cam, 4bl Edelbrock with intake, GT exhaust manifolds and various other things ...). It has a C4 transmission and grandma's rear end (factory 8" with 2.8 gear ratio and conventional differential). I will be putting in 3.8:1 gear ratio. The wheels are factory but will soon be 15x7 Torq D's.

Appreciate your opinions.
 

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I have Detroit Lockers in two of my cars. In the 60's, 70's, 80's the Detroit locker got a bad name because they popped, snapped, tires would scrub (I loved it). All that has been changed (not eliminated) from these units, they are now quiet and smoother. Avalable for 9", not sure for 8" Very tough and dependable!

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What type of locker are you considering? Traction Loc, Detroit Locker, Limited Slip? Any of these would work fine for street driving. The way I see it is if you're gonna go through the hassle of installing new gears, why not? Besides with the gear you're going to pull it may be necessary to keep both wheels planted firmly on the ground.

Every day is a holiday if you love your job.

Current projects: 65 Fastback, 68 Coupe Oval Track Racer, 64 Galaxie 500 XL, 54 F-100 Pickup
 

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With a 3.8 gear, if you don't put something back there you will spin that poor
right tire down to the cord before you get to the store! I have a Detroit locker
and love it. Get one, you won't be sorry!
 

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I love detroit lockers!
I wouldn't take mine out for anything else.

U-turns are a little different because of the clicking, and sometimes the gears will "pop" into place making a loud sound that will probably scare the crap out of you the first time you experience it. Once you get used to it, it just brings a smile...

[color:red]1966</font color=red> [color:blue]V8</font color=blue> [color:red]Coupe</font color=red>
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5 speed, 4.11s, 10.13 in the quarter mile.
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IMHO if you're going to add 3.80 gears a posi rear becomes a necessity, not an option. With gears that tall is will be really hard to keep traction on hard acceleration.
Are you set on the 3.80's ? I only ask because without some sort of overdrive tranny you're going to have a hard time taking your car on the highway. Great gears for off the line, though.
I opted to add a 3.25 4-spider t-lock to my 8" rear. I considered in 3.50, but in looking at the numbers on a desktop dyno it did not seem to make appreciable difference for my occasional street use.
You might also consider looking into the Auburn limited slip systems. They are not as expensive as lockers or limited slips. However, I hear they won't last as long under hard use.
Good luck - Dickson

1965 GT fastback
There's a fine line between "hobby" and "mental illness" - Dave Barry
 
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Discussion Starter #7
There is also a new company called powertrax that makes these gears - there's a writeup on them in this months Mustangs and Fords; supposedly they are silent in turns unlike lockers.

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