8.25 or 8.75

Magnum77 · Dec 21, 2020

Have a few questions. Have a 73 Dodge Coronet with the factory 8.25 rear. I would like to put a suregrip in it and run 3.90 gears. My question is will this rear live behind a 400-450 horse 360? Or should I just replace it with a 8.75 rear? If I were to replace it with the 8.75 rear would it be a direct swap? No welding etc.... I know I would probably have to get the drive shaft taken care of. I would rather run what’s in the car the 8.25 but need some opinions on if it will last. Car will be running a automatic. Thanks

F4R/T · Dec 21, 2020

The 8&1/4 is a pretty tough little son of a gun, if you stay away from slicks you’ll be fine with those numbers, slicks = you better cover your tail IMO.

Outlawd · Dec 21, 2020

8.25 behind 400 to 450 hp will just fine IF your running street legal tires and not going crazy with traction. Whenever you hook up....somethings gotta give. If money or time is not an issue change it out to 8.75 then the door is open for performance upgrades down the road, but these setups are getting expensive now a days.

318willrun · Dec 21, 2020

If you wanted to swap, I believe the 8.75 rear ends that fit are not that expensive and not too difficult to find. You can use your 8.25 backing plates/brakes and shock mounts and that even makes the swap easier. Most of the time the drive shaft will work too, the 8.75 is a little longer in the pinion so you'd want to make sure the drive shaft will work.

Badvert65 · Dec 21, 2020

You will run into fitment issues swapping rears if your Coronet has the isolated suspension, The one that has a box and rubber pads around the rear springs for the axle to mount to. This setup uses an axle mounting pad that has a large centering hole compared to 'normal' mounts. You would do yourself a favor, if your car has this, to eliminate it-even if you stick with the 8 1/4 rear. I had an 8 1/4 behind a big block 74 Plymouth and it lasted until I swapped for an 8 3/4 (because I wanted the option to change gearsets when I went racing.)
jus sayin....

Darter6 · Dec 21, 2020

I did a 8 3/4 swap on a 75 Charger with the ISO rubber rear suspension.
Got everything from a 71 Road runner. Used the spring pads and housing,rear shocks from the 71.Eliminating the ISO.
Driveshaft was the 75. Used the 11'' rear brakes from the 75. Easy swap IF you can find a 71/72 housing.
That said I wouldn't be afraid of using the 8 1/4. Chrysler put plenty of them behind 360 Dusters and Dart Sports.Had one in a 73 Duster with a 380 HP crate Mopar Performance Magnum swap and a 4 speed.

slepr1 · Dec 21, 2020

I'll put money on it that you'll be eventually getting a 8.75 rear sooner or later anyway. We all have good intentions of doing this or that to make it better, stronger and faster. Just prioritise your upgrades and don't do anything half *** or you'll be doing it twice.

8.25 or 8.75

Magnum77

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F4R/T

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Outlawd

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318willrun

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Badvert65

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Darter6

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slepr1

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