Guess on gears in a '74 318 Duster with 8-1/4 rear

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DusterDaddy

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If you had to guess, what gears are in the bone stock rear in my 74 Duster?

The car is a factory 318/904 car with a fresh mild build 318 and a stock 904 cleaned up with a shift kit in it.

Sadly there was nonfender tag and the mice shredded the build sheet under the back seat.

Trans has the stock Mopar high stall converter in it. Have not really driven the car on the street other than a spin around the block yet but I am getting close to that point. I'm wondering how it will behave...
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If you still have it on the lift, just mark the inside of right rear tire and a point on the pinion yoke, rotate tire exactly once and count revolutions of yoke.
 
If you still have it on the lift, just mark the inside of right rear tire and a point on the pinion yoke, rotate tire exactly once and count revolutions of yoke.

A friend advised I do the same. She is home now, but easy enough to jack her up. i could just put the trans in neutral and count the yoke revs with on full turn of the wheel right?

There are many mysteries within this nice little 318 I bought carb to pan. The builder is unknown but it has a purple cam with a .480 lift. That all I know about the cam. The motor lopes really nice at idle. The seller of the motor suggested I stay with the stock "high stall" torque converter so I did.

The seller was a speed shop owner who acquired the motor, which was not fired until it was in my car, when he swapped it out of a Demon that one of his clients bought from a divorce situation. His shop kept the 318 as part of the compensation.

It has Keith Black pistons and the interesting thing is the heads are stock 74 318 heads but they have the 360 1.88/1.60 valves in them and they are very nicely gasket matched and blended.
It has a performer
Intake and a 600 cam Holley street avenger on with with 340 hi-po exhaust manifolds and straight 2-1/2 duals.

I look at it this way. I like that my car left the factory a 318/904 car and it still is a 318/904 car. It just has some
Performance enhancements.

My 69 318 bone stock 2 bbl barracuda would blow the doors off most anything off the line. So this thing should be a hoot to cruise around in....
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I'd guess 2.94 but if you might be super lucky and have 3.21's. 3.23 gears came in the 8 3/4, never in the 8 1/4.
 
I've had two A body 8.25s and they were both 2.45s. Maybe I was just unlucky.
 
Had a 73 Dart Sport 318 904 I bought for he 8 1/4 from a local junkman, I wanted it to have 2.71 but to
my surprise it was 3.21.
 
I think you can mark the driveshaft with chalk and count how many times it "goes around" to one turn of the tire or vice versa.
 
I think you can mark the driveshaft with chalk and count how many times it "goes around" to one turn of the tire or vice versa.
This is friggin bizarre!
Jacked up the rear, car in neutral, rotated right rear wheel 1 full revolution. Driveshaft turned 1-1/8 full rotation.
WTF?
 
This is friggin bizarre!
Jacked up the rear, car in neutral, rotated right rear wheel 1 full revolution. Driveshaft turned 1-1/8 full rotation.
WTF?
That is because your rear end is a open differential. That method works on SG rears. What you are encountering is the spider gears turning.
 
I find new ways to embarrass myself each day...
Well over the winter we will need to get us some gears...
 
Ummm.... you could just pop the back cover off and read it.... :)
 
Ummm.... you could just pop the back cover off and read it.... :)
It stays as is for now. I'll take the cover off in January. lol
My car needs plenty of other things done before I take a perfectly working resr and give it a makeover.
 
Taller gears ain't all bad either if you have the torque to pull em.
You're not the first guy to say that Trailbeast.
The whole project has been an adventure.
The last major thing left is to reset timing after discovering a leaky brake booster then I'll drive it a bit and go from there.
Ignorance, desire and determination are a productive combination, although I'm at this thing for nearly six years....
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You're not the first guy to say that Trailbeast.
The whole project has been an adventure.
The last major thing left is to reset timing after discovering a leaky brake booster then I'll drive it a bit and go from there.
Ignorance, desire and determination are a productive combination, although I'm at this thing for nearly six years....
View attachment 1715091348 View attachment 1715091349

I hear ya, as my car was almost in that condition when I bought it and drove it home 150 miles without knowing anything about it.
I did notice it shifted from 1st straight to third right away, and that almost literally everything was either loose or broken.
Heck after I got the car home I found out all the spark plugs were only finger tight.:D
 
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