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How much will a Ford 8" rear Hold ?

Discussion in 'The Hokey Ass Message Board' started by Retro Jim, Feb 26, 2012.

  1. Retro Jim
    Joined: May 27, 2007
    Posts: 3,860

    Retro Jim
    Member

    I have a Ford 9" rear with 28 spine axles . I am just curious how my HP & torque they will hold . It's from a early Mustang . I am building a 429 to about 450 to 500 HP . Will have a 4 speed toploader and 4.88 gears and going into a 50 Ford . If I do go to 31 spine axles anyone got an idea on that cost ?
    Thanks .

    Retro Jim
     
  2. 8" or 9" ????
    Ford used an 8 in the economy version and a 9" in the high performance line.

    Couple gallons if you fill it all the way up standing on end.
     
  3. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 25,068

    Jalopy Joker
    Member

    need to verify exactly what rearend you have first. guess you are going racing. need to contact a rearend building shop in your part of the world and get an estimate, will not be cheap.
     
  4. Larry T
    Joined: Nov 24, 2004
    Posts: 7,680

    Larry T
    Member

    With 500 hp and a standard, I'd want a 9" with an aftermarket nodular housing and Daytona pinion support (which calls for a different pinion yoke). And that makes 9" a little more expensive.

    "Speed costs money. How fast do you wanna go?"
     
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  5. I' ve heard a 8 in will stand up to about 400 hp. I think a ground pounder with a 4 spd needs a 9 in. Nodular at that.
     
  6. BIG-JIM
    Joined: Jun 13, 2009
    Posts: 1,369

    BIG-JIM
    Member
    from CT

  7. Step up to 31 spline axles if you will be having slicks and a traction device in it. If ur into now is the best time to get a centersection out of a later truck thats 31 spline, call up strange or who ever ur fancy is and get new axles.

    I think a strange kit is 300 ish the last time I looked. I know they are the same price as mooser but had axle bearings and studs and mooser didnt.

    It looks like ur going to be beating the snot out of it so build it once and build it right.
     
  8. Deuce Roadster
    Joined: Sep 8, 2002
    Posts: 9,519

    Deuce Roadster
    Member Emeritus

    [​IMG]

    IF you need a wrench ( not a socket ) to remove the nuts marked in the above photo ... it is a 9 inch. :D

    Opinions vary :eek: but whenever FOMOCO installed engines over 250 HP or so ... FOMOCO installed the 9 inch. Whenever the HP or torque got serious, they installed the 31 spline stuff.

    I would go ahead and go to the 31 spline 9 inch stuff ... NOW ... because if the 429 is only halfway decent ... you will be NEEDING it ... after you break the 28 spline stuff. After Market sources offer 33 and 40 spline 9 inch Ford parts and pieces for the serious drag racer.



    [​IMG]
     
  9. studedudeus
    Joined: Jun 11, 2008
    Posts: 141

    studedudeus
    Member

    Lots of 8" rears being used in race cars at Bonneville. Why? It's a poor man's quick change. Gears all set up so you can change pumpkins when you want to. Also many 8"ers have untapered axle shafts, so even with 28 spline, they are quite strong.

    Engine HP doesn't matter much to the rear end unless you are really hooking up. What tires will be on the car, and are you really going to race it? If only using street tires, even wide ones, you aren't likely to break an 8" rear end. With slicks, you can probably go to about 400 hp on a well built 8".

    Of course, everybody will be more impressed if you tell them you have a Ford 9" rear in it.
     
  10. Deuce Roadster
    Joined: Sep 8, 2002
    Posts: 9,519

    Deuce Roadster
    Member Emeritus

    The 8 inch has less parasitic drag. It takes less hp to turn.
    A 9 inch is just as user friendly ... and has a better selection of gear ratios.

    But @ Bonneville ... traction is not the issue. Traction and decent HP is what breaks most rear ends.
     
  11. tommyd
    Joined: Dec 10, 2010
    Posts: 11,395

    tommyd
    Member
    from South Indy

    I have run an 8" for about twenty years in my Fairlane. Had a 4500 converter,4.11's and a decent 302 with small slicks. never broke anything and that was a lot of heavy summer racing running 12:60's. Whatever horsepower it takes to do that..maybe 375? I would still rather have a 9' because it just looks right. I would say a heavy car with 400hp would trash an 8" on a regular basis.
     
  12. 62RagtopNova
    Joined: Feb 5, 2012
    Posts: 117

    62RagtopNova
    Member

    Bingo.

    I had a 9" Currie custom built for my Nova and they do a great job. John or Ray will hook you up.
     
  13. Hotrodbuilderny
    Joined: Mar 20, 2009
    Posts: 1,646

    Hotrodbuilderny
    Member

    I had an 8 inch in a 67 Nova with a small block 4 speed about 35 yrs ago, 4:63 gears,car went 11.60's never broke in the time I ran it, that being said If you are starting from scratch go for a nine inch. A 28 spline rear with aftermarket axles, if you already have a posi should be good,if you are going to be shopping then I would use 31 spline,a lot of trucks and Bronco's came with 31 spline 3.50's good starting point for a carrier.
     
  14. Retro Jim
    Joined: May 27, 2007
    Posts: 3,860

    Retro Jim
    Member

    Thanks for all the opinions and help . YES it will be doing some street & track time for sure ! Going to be building an Old Skool 1950 Ford Gasser the old way with parts you would have found in them back in 1972 . I am building it on a shoestring budget and so far is going very well . I have a new Lakewood blow shield , new sfi flywheel and newly rebuilt 4 speed toploader close ratio trans . I have a 1970 Ford 429 with dove heads I am going to be building , myself since that is what I do . I am buying a 3rd member with 4.88 gears from a friends car he has . They only have about 500 street miles on them .
    I figured I would ask the question but kind of knew the answer already . I just wanted to make sure before I traded for the rear ! I have a chance to get a complete 9" rear with 28 spline axles for $150 with garbage gears . He was going to trade me for my Xbox 360 with 4 games I really don't use . I was hoping the axles would be 31 spine but not lucky enough . The 3rd member I am buying is a 4.88 posi but 31 spline . So I needed the Mustang narrow rear housing for my 50 Ford .
    Well since I am going to have to buy new axles anyway . So I just as well buy the Mustang narrow housing from a friend for $50 and just buy the axles and be done with it . That way I know the rear will hold up for a good while .
    I was going to buy Moser axles but I want to thank "shocker998md" that told me about Strange axles that come with new bearings ! That will save me some money ! I will be checking with them to make sure along with Currie .
    Thanks to everyone for the help !

    Retro Jim
     
  15. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    falcongeorge
    Member
    from BC

    An 8" behind a healthy 429 and toploader with 4.88s and slicks? Your kidding, right?
     
  16. wisdonm
    Joined: Jun 20, 2011
    Posts: 436

    wisdonm
    Member

    With a 429, you better get the 9". I run a 8" with about 400hp, but it's 302 and the car weighs only 2,500lbs.

    Do you have an 8" limited slip that you'd part with?
     
  17. metal man
    Joined: Dec 4, 2005
    Posts: 2,948

    metal man
    Member

    My guess is about 3 1/2 gallons.
     
  18. No problem man, I was looking at building a 9 inch in the future for my F100 and found out about stranges pricing. Thats what ill be using.

    You have a locker for it yet? Since ur doing 31 spline look at the used NASCAR lincoln lockers, there priced pretty good!
     
  19. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    falcongeorge
    Member
    from BC

    ^^good tip. Thanks.
     
  20. Von Rigg Fink
    Joined: Jun 11, 2007
    Posts: 13,428

    Von Rigg Fink
    Member
    from Garage

    I read somewhere 300 HP.
    and it all depends on if you can make it hook up or not.

    a light car with 300 or 350 HP..and it cant hook up..if the 8" is built right it will take it.
    abuse the shit out of it? pay as you go
     
  21. Tom S. in Tn.
    Joined: Jan 16, 2011
    Posts: 1,108

    Tom S. in Tn.
    Member

    Used to narrow up 8" Ford to use in jr/fuelers. Light weight and minimal drag, and used spider gears with resplined stock axles. Some had the carrier cross drilled at 90deg for a second pin and used 4 spider gears.
    Limited ratio choices, but an 8" is great in a light car. Tom S. n Tn.

    Let me add this; in my experience, I believe an 8" is tougher than a 12 bolt.
     
  22. Tom S. in Tn.
    Joined: Jan 16, 2011
    Posts: 1,108

    Tom S. in Tn.
    Member

    One more funny thing about Ford differentials; the fill plug can be in the carrier housing or the axle housing. Take note. It's possible to put together a combination that you won't be able to fill with grease when you get through.
    Don't ask how I know this........ Tom S. in Tn.
     
  23. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    falcongeorge
    Member
    from BC

    Light cars and minimal shock loadings. 8 3/4 Mopars were used in diggers alot too, but I have made them spew in stick street cars with sticky tires.
    But then again, I have broken a few 12-bolts too.
     
  24. rustang
    Joined: Sep 10, 2009
    Posts: 710

    rustang
    Member

    I run an 8" with 28 spline axles behind my 375-400 horse smallblock and toploader, with drag radials... the 8" is more expensive (for centersections) than the 9", and the 8" will be good to about 400-425 HP.....

    Behind a big block I would use a 9", preferrably with a nodular case and 31 spline axles.....look for a 60's-70's pickup for a good core... they are out there.
    Tom
     
  25. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    falcongeorge
    Member
    from BC

    I am honestly surprised that the 8" will live behind that. Do you race it much? How many hits on the ring & pinion?
     
  26. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,375

    gimpyshotrods
    ALLIANCE MEMBER

    I know exactly how you know this. It is exactly how I know this.:eek:
     
  27. Uptown83
    Joined: Apr 23, 2007
    Posts: 722

    Uptown83
    Member

    I run an 8" in my 33. Dyno'd at 550 HP. I've ran it hard a couple of times and no problems. I was worried when I first built the car but never think about it now.
     
  28. koolkat269
    Joined: Jun 5, 2011
    Posts: 172

    koolkat269
    Member

    Let me guess, like trying to get oil in a small block chevy with old style valve covers and a newer style intake? :rolleyes:
     
  29. Tom S. in Tn.
    Joined: Jan 16, 2011
    Posts: 1,108

    Tom S. in Tn.
    Member


    ........... you to, huh :)
    Tom S.
     
  30. greaser
    Joined: Apr 30, 2006
    Posts: 838

    greaser
    ALLIANCE MEMBER

    I appreciate all the input on this thread! I personally value the opinions of those having real experience using the 8".
    Is the successful use of an 8" with less than 400 HP based on using a Trac Lok Posi unit, or non posi? Kinda sounds like a strange question, I know, but I'm trying to realize the overall effects including minimal "hook-up". These hot rods we build are pretty light in the ass end.
     
    Last edited: Feb 29, 2012

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