I am trying to figure out what would be the best gears for my Duster. I want improved acceleration and decent cruising ability. Would 3.23s be my thing? What about 3.55s, is that too low? It has 2.76s now and they suck unless you run over 75 MPH all the time. It has 215(I think)/70/14 tires and a 904. Some people say that I want feel any difference with 3.23s and others say that 3.55s are too low? Any good personal experiences?

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

You will almost certainly hate 3.55s after about a day and a half of having fun with how easy it'll be to squeal the tires away from a stop. The car will be obnoxiously loud and thirsty above about 50mph.

2.76s are indeed highway flyers. The guys telling you that you won't feel a difference with 3.23s are smoking drugs or something. 3.23s work very well for multi-purpose usage as long as you've got decently-sized tires such as the ones you describe having.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks Dan. I guess it is 3.21 gears for me. I have already found a good rebuilder for my A body 8 1/4.

Might sound kind of silly, but will I be able to spin the tires with 3.23s? I have a stock slant with a super six and no emmisions equipment.

I just wondering if I would need to spend the money for a posi or not.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

If you do much freeway driving, 3.23's are the most I would go. In my 71 duster with 3.23's I was pushing 3500 rpm and climbing at 70+mph.

Swap a 8 3/4" in and start collecting center sections from yards, you can then experiment with ratios without to much hassle swapping between them.

No to the posi for a stock or warmed slant not worth the money the 7 1/4 is strong enough as it is let alone a bigger rear.

Smoking tires has lots of factors to it not just rear gears. Just remember the more time you spend spinning tires standing still is the less time you spend accelerating.

Thanks Pierre. Down here A-body 8 3/4s are ridiculously expensive and they are the wrong bolt pattern. I saw a complete one sell for $650 last week. I have a free A-body 8 1/4 in my backyard and it will be more than adequate for my application.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

I had a '76 Aspen with the A833 OD, 3.23 gears and it would blow off the tires. In my opinion a stock 225 automatic is ok with 2.76 gears and shorter tires. With your size tires 2.94 gears work out to be nearly the same RPM as the 2.76s with a 185/80R13 like some of the guys with older cars still roll. 3.21 is a decent compromise.

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Joshua

Jeb - I know what you mean about 8 3/4 - I was lucky to find an A-body 8 3/4 so I wouldn't have to mess with bolt pattern. Whats in the currently 8 1/4" you found?

fyi, for perspective - when I had 2.76's out back I was turning ~ 2500rpm vs 3500rpm with 3.23's this is with 205/70r14 tires - 904 tranny.

That can't be right. If you're turning 2500 RPM with 2.76s you'd have to step to 3.86 to get 3500 RPM. 2500 RPM with 2.76s calculates to 2925 RPM with 3.23s.

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Joshua

Hmph... it was a few years ago so that 2500 figure may be off, with different converter so comparison may not be completely accurate. But I recall the spread being closer to 1k which surprised me too. Or perhpas one was at 60mph vs 75 or something... Ok fine ignore the figures if you choose to then

Is converter slippage consistent throughout rpm range?

If you want something to toy with.... http://www.moparts.com/Tech/tech/img/AUTOMATICchart.xls

No, percentage wise there's more slip at lower rpms, with a much greater percent if you're below the converter stall speed.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

The speed/rpm/tire size calculator is fun. Thanks Pierre.