is the 7.25 diff sturdy enough for track use in a A body with built slant ?found a site that has sure trac / posi units for these, or would I be better off searching out a 8.25?
https://www.drivetrain.com/


also is the 7.25 like the 8.25 in that there is a carrier size for gears above
2.71 and a carrier for gears below that size?


thanks

I certainly wouldn't use a 7 1/4 with a manual trans at the drag strip with a modified engine. Shock loading kills parts and hitting those little spider gears with a harsh clutch engagement breaks them. The older Power Lock style Sure-Grip has 4 spider gears and is much harder to break.

It costs almost the same to build a 7 1/4 as an 8 1/4 or 8 3/4 as most all the individual parts like bearings and gears are very close in cost. Only the cost of admission is different. If you are starting from scratch and would like to be able to change gears via relatively quick and easy 3rd member swaps the 8 3/4 or a Ford 8/9" is the way to go.

My Valiant has a 3.21 geared 8 1/4. This is my compromise gear. It comes off the line reasonably well and I can stand it on the highway when I drive 100s of miles to slant six bracket races. My '72 Dart has a Ford 8" out of a Granada as it was cheap and bolted right in with a conversion U-joint. My departed '66 Dart had an A-body 8 3/4 with cut down C-body wagon axles. FYI, using big car or pickup axles in the A-body 8 3/4 housing makes the rear end about 3/4" wider overall. My '66 Barracuda will get a narrowed to stock A-body dimensions. I want to be able to swap gears in the Barracuda as I will be using the car in a few different venues and I have an investment in 8 3/4 3rd members.

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Joshua

8 3/4 would be nice,, but they are expensive,
there are lots of 8 1/4 around here at the pull a parts in D-150's and rwd vans, that are affordable

to get a D-150 8 1/4 cut down to A body size,,I can visualize shortening the axels, having the splines re-machined in,, but what about the axel body itself,, is that a simular process? would one section out a length the axel carrier on each side ,then re-weld it together? That what I am not understanding,, the housing seems to critical to be re-working.

8 3/4s for A-bodies are expensive, but others aren't that bad especially if you get one from a C-body or other less popular car or even a van or pickup. 8 3/4s don't have C-clips like 8 1/4s and late 7 1/4s do. The axle bearings in an 8 3/4 are also better. It costs the same to shorten an 8 1/4 axle as an 8 3/4 axle and the axle has to be thick enough to be cut down and resplined. For an A-body width axle the only suitable axle donors are late C-body wagons and pickups. If you have to get custom axles the expense goes way up.

Take a look at this web site to get a handle on the operations necessary and the costs associated with narrowing a rear end. http://www.dutchmanaxles.com/ You'll quickly see why I chose to bolt a Ford rear end under my Dart.

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Joshua