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Ford 8 Inch Rear With Posi

Discussion in 'The Hokey Ass Message Board' started by MUNCIE, Jan 27, 2010.

    Joined: Jan 24, 2006
    Posts: 2,116


    Ok I tried the search option and nothing specifically came up on this.Plenty out there on 9 inch rears but whatabout the 8's ? It seems it could hold up to some abuse on a low hp application.
    I was checking around and was wondering if anyone out there might be running this type of rear and if so do you have a posi installed? Also what about buying the whole 3rd member new how much would it set me back? I had a rear that I picked up out of a 67 stang but after opening up the pumpkin.The gear ring semmed to have rust on about half the teeth so I'm just going hold onto it for now.It seems it may have ben sitting in some water or something.

    So I got another rear from a 65 mustang and Im going to use the same axles and housing but want to replace the whole pumpkin with new guts.I am going to try any swap meets that are coming up maybe I can find a used one in fairly good condtion to save me a few fahzoolas.:cool:
    Probably isn't much 8 inch enthusiasts out there but if so any input or knowlledge would be appreciated.
  2. cracker head
    Joined: Oct 7, 2007
    Posts: 918

    cracker head

    I got a new one off ebay, Yukon gear makes them. Supposed to be pretty decent unit, have not installed mine yet.
  3. carcrazyjohn
    Joined: Apr 16, 2008
    Posts: 4,846

    from trevose pa

    Im using 8's also Ill be following this thread ,I want to jump up in the 3,50's gear ratio also .
    Joined: Jan 24, 2006
    Posts: 2,116


    Cool I mlooking tat some 3.25's right now.Want to be able to hit the highways a bit and not over rev the engine.I'll post up some pics of the break down and hopefully the build up if I can find the parts for the right price.Got qouted a little under a grand for just the whole new 3rd member with the posi,gear and case ready for install.Not sure of the gear brand though ?
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  5. actually , i think there are a lot....8" rears are common in hot rods , i have one in my `36, but not with what i believe ford called Trac-Loc? there wasn't a lot of them produced with one. the only one i have seen in person was in a car that i bought new in the 70s

    as it seams you have discovered, they can bring big $$$
  6. cracker head
    Joined: Oct 7, 2007
    Posts: 918

    cracker head

    My car has 3.50 gears, 6.70 15s and a c4 trans. I dont have a tach in it, but its not twisting too much, in my opinion.
  7. cracker head
    Joined: Oct 7, 2007
    Posts: 918

    cracker head

    I think I paid around $325 for a new posi unit.
  8. Jalopy Jim
    Joined: Aug 3, 2005
    Posts: 1,868

    Jalopy Jim

    I have an 8" for my Falcon project. 3.05 gears. I lookibg at about 350HP / 350FT lbs with a T5WC infront of it. And 215/60 tires on the back.
    I do have a concern if it will hold up.

    jim h
  9. mikeco
    Joined: Nov 3, 2008
    Posts: 393

    from virginia

    I've had several with no problems. Seems like everyone wants a 9" around here. I have an open 8" pumpkin with 3:00 gears & can't give it away.
  10. BLAKE
    Joined: Aug 10, 2002
    Posts: 2,688


    We put a 3.55 Trac-Loc into the 8-inch in Joyce's pickup... bought the center section from a trusted seller on eBay. No complaints here.

  11. Hotrodbuilderny
    Joined: Mar 20, 2009
    Posts: 1,649


    I had one in my 67 nova back in the 70's, had a 337 4speed, car went 11.80,
    never had a problem,the only aftermarket gears at that time were 4.63 and 3.50 I don't know what gears are available now I have been building rears for 38 yrs I may have been asked to do maybe 3, 8 inch rears in a light vehicle should handle moderate abuse v8 axles are the same as 9 inch 28 spline good luck
  12. FONZI
    Joined: Mar 5, 2001
    Posts: 1,530


    It has always been my understanding that the 8" is a "descent" rear end and a pretty inexpensive option in stock form. However, if you are going to put any real power to it you may as well step up to a 9" cuz you will end up spending the same if not more beefing up your 8"
  13. waldo39
    Joined: Sep 8, 2007
    Posts: 41

    from Illinois

    Been running an 8" at Bonneville with 530 hp with no problems. Trac-loks are expensive now. You can get bearing kits, gears and all from Summit in Ohio. I'm using 8" ones in my next 2 projects.
  14. Hnstray
    Joined: Aug 23, 2009
    Posts: 8,349

    from Quincy, IL

    It seems 8" Ford rears have been the "ugly stepsister" of the 9"........but there is not much basis for the disrespect. What makes a 9" so strong, the third bearing at the rear of the pinion, is also present in the 8". Hence it is stronger than the typical rear end from other makes with similar size gears. Also, the axles in 28 spline 8" are mostly the same as many 9". What I like best about the Ford stuff is the axle bearings that DO NOT use the axle shaft as a bearing race and save axles for another go round if the bearing fails. And, the drop out 'pumpkin' sure makes diff work much easier. The only complaint I have with 8" is trying to find used 3rd members with the gear ratios I would most like to have.....i.e. 3.25/3.50 and up.

  15. Drive Em
    Joined: Aug 25, 2006
    Posts: 1,742

    Drive Em

    The 8" housings are the weak link. Get a car with some HP, sticky tires and a good launch and you can rip the spring mounts off the housings.
    Joined: Feb 9, 2003
    Posts: 682


    What he said!
    I cant find anything in my area, and when you do ur gonna pay for it.
    On the other hand tho.... I like them, stock 8" can be had for $30 to $40 bucks.
    Ive used them in lotsa things..... A-Models etc.
  17. solid
    Joined: May 20, 2007
    Posts: 1,459


    I bought an 8'' for a 66 mustang(not a trac-loc) at a yard sale this fall for $25, he threw in the driveshaft. It is already cleaned up nice, with new brakes. It was going in street rod, but the guy building the car for him "suggested" he use a 9''.
  18. 65COMET
    Joined: Apr 10, 2007
    Posts: 3,086


    I drag raced with an 8" for years.What finally broke was the third member all around the pinion support,a base 9" will do the same.A base 28 spline 9"and a same width 8",use the same brakes and axles.The 8" will put up with alot until you put sticky tires on and drop the hammer at the track.I mention all this thru actual experiance,not hearsay. ROY
  19. newfalconowner
    Joined: Jul 26, 2009
    Posts: 810

    from NS Canada

  20. Algoma56
    Joined: Jan 18, 2006
    Posts: 880


    Unfortunately, the one I took out and used in my 47 coupe with Granada rear, was a 3.00 open. Mustang !! had a 302 automatic in it. Still was a step up from the 2.79 ratio.
  21. Von Rigg Fink
    Joined: Jun 11, 2007
    Posts: 13,431

    Von Rigg Fink
    from Garage

    got one under my current 28 a tudor project..

    completely re brakes, new seals, new gear set..cant wait to see how well it acts.

  22. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 18,286

    Jalopy Joker

    Ya, if you are into big HP and monster burnouts go for a 9". otherwise a 8" will do the job. currently have one behind a 355 HP 350 with 10" rims and 50 series tires. nothing broken with a once in a while burn out. you could always run an open till you find a trac-lock. put ad in wanted her, on craigslist, etc. I found one I have thru an ad in Hemmings. it will cost some bucks for a shop built one or from a place like currie. $250 on up for good trac-lock.
  23. Southfork
    Joined: Dec 15, 2001
    Posts: 1,459


    Some of the Mustange II's etc came with 4 lug wheels didn't they? Any of them have tracklock?
  24. thirty7slammed
    Joined: Sep 1, 2007
    Posts: 887

    from earth

    Im using a 8" maverick in my 37, it's a good honest 300 h.p., 3.55 gear, auburn posi pro, worked great for a couple years, now both wheels don't always lock up, with that said im not a big fan of Auburn posi tracs. But I think 8" rears have their advantages , the mavericks fit well in fat fender cars, are fairly common, and you can usually pick one up for $100.00 bucks, and unless you got 400 + h.p. and hammer on it all the time should hold up well. Don't get me wrong, Id rather run a 9", but most of my stuff is on the cheap, not that I believe in sacrificing safety, but I will use a more economical part if it is compatiable with my other running gear. Im also running a 8" in my 40, but it's a single trac 3.25, just one mans opinion.
  25. holeshot
    Joined: Sep 18, 2009
    Posts: 1,520

    from Waxahachie

    MUNCIE...yea most dragcars run the 9 inch for a good reason. 3 teeth on the pinion are ingaged at all time. but the 8 inch only has 2. so unless your drag racing ever week, you'll be fine...POP.
  26. clays diff
    Joined: Feb 3, 2006
    Posts: 44

    clays diff

    20 years ago my friend at us gear sent me a print on how to take a 9" traction lock and make it a 8" the left side of the case is the same. the right side is different you have to turn the bearing journal back .750 and turn the fins down till it looks like the 8" very simple to do i have done a ton of then in the last 20 years also you use 102949 bearing and 102910 race hope this helps you guys out

    Clay >>>>>>>>>
  27. MUNCIE
    Joined: Jan 24, 2006
    Posts: 2,116


    Wow glad to see the topic being discussed!! Thanks everyone on here for all of your input and suggestions.I had a little time this afternoon before I headed out to work so I pulled my axles and the whole 3rd member out.I took some pics and will post them tomorrow because I was in a rush and like a dummy left the camera at home.

    After I clean the housing up real nice I am going take the axles to get the bearings pressed on and knock out the seals and get the whole bearing kit so I can have the new ones pressed on.Then I got to wait a few weeks to come up with the all the cash for the brand new setup 3.25 with posi us gears.After that assembly time then on to the brakes.I will be posting pics on here of the build so you guys can check it out.

    I don't think my engine will be creating any serious horsepower but it is a solid built 289 built to 302 specs.No serious head work done yet but maybe later on in the future, I might add a slightly larger cam than the stock one that is in it right now.Just want to try and get it on the road and upgrade as needed.

    Thanks once again everyone,
  28. MUNCIE
    Joined: Jan 24, 2006
    Posts: 2,116


    Here is a shot of my axels.Not sure if the one in the lower part of the picture is good.Has a slight blueish discoloration about an inch over from the bearing.The housing just a shell now got the seals knocked out and the backing plates cleaned up.Time for the car wash to clean it up.

  29. slepe67
    Joined: Jan 22, 2008
    Posts: 1,146

    from NW MT

    INFO NOTE: This month's Rod and Custom has a build up of an 8 inch

    I had a 9 inch in my 67 Mustang/built 351C/FMX, and I ran 12's with it. Just rebuild it, and toss in a mini-spool. If ya don't mind clunking when you turn sharp corners :)
  30. The Shocker
    Joined: Dec 30, 2004
    Posts: 3,540

    The Shocker

    8 inch rears are fine for a streetrod ,but not the best in a drag car. Heres what happened to mine a few years ago with a mild 302 Ford (proly 350 horses), a 4spd Toploader ,and a 6700 powershift into 2nd on a sticky dragstrip ,in a 2600 lb Falcon with plain street tires .The left side bearing cap broke off while the bolts remained .The left axle snapped off as well .It had a minispool in it with a hardened pin ,and when it let go i nearly hit the wall as it turned hard to the right.Ruined a brand new set of 4.10 Richmond gears in the process ,and knocked a huge dent in the rear of the housing when the cap broke and shoved the ring gear back.Moved up to a 9 inch after that ,but never got a chance to race the car again before i sold it...

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