Should I narrow a nice 8 3/4 rear for my FED or get a new fabricated housing thats a 9 inch for my FED project. Its early hemi running in the low 10's so I don't thing it woul be too much for the 8 3/4. mainly looking at price which would to more affordable and which woul be lighter
If you are reffering to a 8.8 as an 8 3/4 then yes it is plenty strong. The on factor is car weight, and they sell alot of struts and houseing covers to bolster them more, But rail is light so you should be fine. I have a short 9 inch housing here, that was an extra for a fed back in the 70's....It was never used, has surface rust, let me know fi your at all intrested.... I run an 8.8 in my Mustang, with strange 33 spine axles, c-clip elim kit and spool. My car weighs around 2000 lbs with me in it. I have turned low 10's, with out ever an issue......
The Mopar 8 3/4 rear is excellent. They're all 30-spline, and the pinion bearings on the -489 case are the same size as the Ford high-dollar Daytona pinion bearing... and the Dayton bearing is only one of the two... the inner bearing is smaller, and then there's the real small third bearing. The casting that holds that 3rd pinion support bearing is often a weakness, not a strength. Half of that casting is just hanging out there in space, and it's not uncommon for them to break off, sending chunks into the ring gear. Also, depending on how hard it hooks, I've seen the whole pinion support area on the drop-out section break on a 9-inch. Finally, if you're going to run a posi unit, the factory difs frequently break between the ring gear bolts. None of that is a factor on the Mopar 8 3/4. A little more info: In stock form, a Mopar 8 3/4 is a good bit stronger than the Ford 9-inch. In aftermarket form, a Ford 9-inch will handle a lot more power than a Mopar 8 3/4... but it's going to take a lot of high-dollar aftermarket pieces to do that. At which point, it will be cheaper to build a Dana 60, which won't ever break. Yes, I know I'm in the minority, but I believe there really isn't a need for the Ford 9-inch... Build a Mopar 8 3/4, and when the ring gear teeth strip, go with a Dana. -Brad
I had housing problems on the 8.75 489-series rear in my backhalved car, but the centersection never gave me any trouble. Once you narrow one down far enough to fit a FED, there's not enough housing width left to give you any trouble. Backbrace is a good idea.
The Mopar rear has slightly less internal power loss, too, due to a higher pinion. Less "scrub" between the ring and pinion. It ain't much, but it's there!
Mine has an 8 3/4. Plenty strong for anything you throw at it with the right axles. 35pline should get you past 700hp with ease. They are lighter than a 9inch and do have a different pinion height. This is important if you are installing it in an existing chassis as it will alter the height. 9inch parts are cheaper and more plentiful used, but if you are buying new there is not much difference. And way more traditional. Go with the Olds houseng ends and bigger bearings.
I can get a 8 3/4 bare housing to narrow for $50 opposed to an already narrowed fabricated 9 inch for 500 so I think I am going to pick up the 8 3/4 and go from there. Thanks guys
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