Looking at putting a 9 inch in the Duster and I'm a little overwhelmed with the choices so thought I ask for some help. Car is 3100 lbs with a 727 and no transbrake, 600 hp, 600 torque. So it isn't going to be super hard on a rear end but it does need to be beefed up from stock.

I'm leaning towards a Strange nodular case with S Trac differential. I think I could get by with 31 spline axles but 35 spline doesn't seem to be a huge cost adder. I'm going to use the Torino ends since they work with the disc brake kit that I'm planning on. I'm not sure about 28 or 35 spline on the pinion. So I guess it boils down to which spline count for the pinion and axles?

Seems like there are more gear choices in the 28 spline pinion while the 35 spline pinion is pro gears only. So maybe I should steer clear of the 35 spline pinion. I also see that there are different pinion shaft diameters with the 35 spline setup so that means the pinion supports are different. I can see how a person would get lost in this stuff!

I wouldn’t run anything less than 35spline axles. Torino ends are perfect, you’ll have tons of brake options.

You’ll need at least the 3.25” bore case and the 28spl pinion is fine. The nodular cases are strong, but heavy. I build a lot of the thru-bolt aluminum cases as the cost difference is negligible. With a 9” as well you can buy different length yokes so you might be able to keep your driveshaft with some playing.

Strange makes 2 different aluminum cases that are non thru bolt. One is a lightweight street type case that’s like $325. Those won’t hold up to drag racing. The other is the same they put in the Copo’s. Nice piece but obviously more pricey.

Something like this is 375.

I had a Strange Pro Iron case and it was very heavy. I switched to the Yukon bolt-through aluminum case and it makes gears changes much easier. I have two setups with different gears. I also use a Detroit locker. I had to remove a little material in the Yukon case with a die grinder to make it fit though.

Checkout Quick Performance in Iowa , they built me a custom narrowed 9" housing and 31 spline axles for my 65 . It was like $750 . shipped to my door within a week .

Thanks, that is exactly where I was going. From what I've seen so far the 35 spline axles, Torino ends, 28 spline pinion all seem to be good choices. I'll do more research on the bolt thru cases and front supports. I have a Strange 8 magnet setup on my Dana 60 so I need a pinion yoke that will accept that. I'll use a 1350 u joint. I have a Detroit Locker now and I'd rather switch to something else. I have a S Trac in my other car and I like it so I think I'll put an S Trac in the 9 inch as well.

Why are you wanting to move away from the Dana?

I've considered trying something different as well. Lockers have their drawbacks. I'm making more than 600 HP and just haven't found something that I trust to hold up, yet.

I have been building a parts list to go back to a 9" too. That Yukon through bolt case looks plenty strong and the 28 spline input is plenty strong on the pinion. My old 9 had 33 spline Moser axles and spool still making passes in a 9 second Camaro with a factory double rib iron carrier. I looked at the S-Trac for my future build but the $1000 price tag doesn't fit my budget but Cass could probably get you a better deal on that unit. I like the round back housing just because it looks like an 8 3/4. I ran the Italian made Summit brand 4.56 gears in mine and they are still going strong many hundreds of passes later. You should be able to find the yoke you need easily and the pinion support gives you plenty of options for mounting it to the housing.
Good luck with you new project I know you will like it

Gus

I'm planning on putting Weld S71 wheels on the rear to match the fronts. The offsets will be different so the axle lengths need to be changed. The gear ratio in the Dana is a 4.56 but I only need 4.10 for the way I'm using the car and I'm thinking of changing brakes as well as the differential. Rather than pull everything off the Dana 60 and try to sell a bunch of used parts I think it will be easier to just build a new rearend that drops into the car and then sell the S60 as a complete unit to someone who is building a drag race A body. I could also have a new S60 built with all the parts I want but I think the Ford housing will give me a little more room under the car. It looks like the Ford costs a little more money than the S60 but not a huge premium if I stay with bracket racer parts rather than pro parts.

While they have some drawbacks spools are predictable and reliable. About the only time I don't like the spool in my street car is in parking lots. Some people on here act like a spool will kill you in the rain, its not bad, and its predictable. A locker is more likely to come around on you when it transitions from ratcheting to locked. My Jeep has had a locker in it for 15 or so years and it wants to kill you in the rain, you just have to know when its going to make its move lol.

I don't think anyone makes a 35-spl TracLok, only a 35-spl Detroit Locker. If there is a 35-spl T-Lok, I'm interested to know who makes it.

Strange stuff is first class. The iron pro series or S series should be fine for what you are doing. They don't want the race axles used on the street. That doesn't mean guys don't do it. I would just go straight to 35 spline alloy stuff in a car that would be primarily be used on the street. 35 spline (funny car) pinions are typically used in big power race applications and are pro gear only. 28 spline is fine for most stuff below Top Sportsman level performance.

Anything you can get from Strange in a package vs. individual pieces saves a bunch of money.

I have some MW stuff that came out of my Drag Pak. But it's a spool. (You probably don't want that.) And it would probably not have the right length axles or we could make a good deal.

Had about every type rear posi you can have. The only one i hated was a Detroit Locker.

Why not a spool? I've ran one for the last eight or nine years with no issues.

Just remember a cheaply built 9 inch is no better than an 8 3/4.

There is no way I would spend money on a nine inch rear end, no matter who made the parts.
I would spend money on a 10 inch rear end with a drop out third member as long as it had over 1000 HP with a high traction chassis
I remember when the Chrisman family was developing the Ford nine inch rear end for drag racing, they used the Dunn and Reath funny car as their test mule. Joe Reath told me that they had over $2300.00 in it back in 1972 or 1973, he also said they would take it out of the car and put the Dana 60 back in it when they where racing the car in Salt Lake City, UT I didn't think to ask why they would change it for racing it up there

Lmao. Ohhhhh ok 👍

Is this a drag race or street/strip car? I use Speedway Engineering housings, but thats more suited to circle/road race. If your going custom 9", I'd go full floater. Multiple advantages such as the axle shaft doesn't carry any vehicle weight, brake pad knock back is eliminated, etc... 31 spline would be more than enough for your power level, but I'd opt for 35 to have some cushion, albeit at a weight penalty over the 31. As far as center sections, I use the iron Strange pro case (big bore for 35 spline). Aluminum cases move around a lot and eat up gears on road race/circle track applications. Same for the pinion support, iron Daytona. Differential wise, the Strange unit is almost identical to the Wavetrac, except the Wavetrac has a lifetime warranty. I chose the Wavetrac, in part due to warranty.

The S-Trac has a lifetime warranty too.
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