8.8 REAR VS 9"

Discussion in 'Classic Mustang Specific Tech' started by brianproctorla, Jul 3, 2007.

  1. I am looking to swap a ford 9" into my 65 mustang.
    Ideally I would like a POSI.
    It seems to me that the ford 8.8 rear is cheaper, lighter, more likely to have a traction-lock center, and offers more disc brake options.
    Is the major problem with these rears the pinion offset?
    If I have to relocate the perches and narrow the housing, it seems like this shouldn't be that big of an issue.
    Can these axles be shortened? In know 31 spline axles can be resplined, but am unsure of 8.8's.
    Is it cheaper to shorten a 31 spine 9" axle or order a new axle?
  2. Pinion offset can be a hassle, depending on year

    Depends on what year you have - I believe there is a thread if you use the search that explains how the modern Mustang 8.8 and Explorer fit in a '65-66 or a '67-70. I basically determined for my '70 that 9" was the way to go, not because of durability issues with 8.8, but that the rear diff I want (torque sensing, Torsen or Black Gold) seems mostly available in 9", and the housings are easier to find with the correct offset for a '67-70.
    If you're junkyard Explorer or Mustang cannibalizing on a budget, it can be done with an 8.8 without too much effort from what I gather. A lot of guys don't like the c-clip design of some of these rears, though, but it really depends on how much power you're putting into it.

    good luck!
  3. 9" is the way to go. But, the correct width is the fun part. Didn't 9" housings from late 1950's fords fit?

    But, on the 8.8 you can put on rear discs.....
  4. Who says there are more brake options for an 8.8 than a 9"? The 9" sets the standard, and if a kit is made for anything, it will be made for the 9" first.
  5. Thanks Guys

    I have a 65 Coupe.
    I was planning on putting a 67 ford 8" into the rear, but a 9 or 8.8 would be "top of the line"
    I have thought about various engine combinations.
    Right now, I'm considering putting in a 250 6 cyl , with the new classic inline aluminum heads, with an AOD transmission. I'm in the process of swapping out the entire suspension and braking system.
    I would like to have the option of going in the opposite direction and putting a 351w in there as well.

    Did 8.8's come with 31 spline
  6. I think it might be easier to locate a used disc setup or big rear drum setup for an 8.8.
    Plus the posi units for 8.8'S seem to be quite plentiful
  7. Any one know the dimensions of the 8.8 rear ends? Width?

    EDIT: If I were to swap out my 8" rear for an 8.8 I could get one with disk brakes already on it, and save myself the dough I'm wanting to drop on the SN95 disk brake kit. Course my roommate's got a set of rotors off his 05GT he ain't using no more. It would also allow me to get a posi rearend in the stang at the same time.
  8. 8.8 did not come with 31 splines. I pretty sure they are 28's.
  9. If the 8.8 axles are all 28 spline,
    that means that they can not be shortened, which could be a drawback.
    I imagine that it is cheaper to shorten an axle than it is to buy new ones, correct?
  10. off hand, the housings that will fit directly into a 67 stang and have the same perch spacing would be:

    67-70 mustang
    67-70 cougar
    57-59 big ford car
    most fairlane and torino from 66-72 but they are gnerally wider than a stang unit
    71-73 mustang: same as torino and fairlane
    75-80 granada, monarch and versailles some of which cam with disc brakes but not all of them are disc some have 9" with bigger drums.

    IIRC 66-77 bronco have about the right width but the perch spacing is different
  11. ford explorer 8.8s were all 31 spline. None of the 8.8 axles can be shortened and resplined due to case hardening. What you want for your 67 is an 86-93 fox mustang axle. it is just about the right width and you don't have to shorten it. downside is you need to scrounge 2 axles from the same side of an aerostar or ranger with drums to convert to 5 lug. if you aren't making over 400 hp the 28 spline axles are more than adequate to use as-is.

    P.S. be careful and do your research, alot of people are quick to comment on 8.8 tech when they don't know the full facts. i was in your shoes a little while ago and i got told alot of incorrect info. so ask me how i know :)
  12. If you want a 9" for a 65 the best rear to use is one out of a 57 thru 59 Ford. The width is the same and the spring perches are the same width. It's a simple swap. I gave $100.00 for mine but it's not likely that I could do it again. They usually have low gears but I've never seen one with a locking rear.
  13. Anyone know what the actual length of the 8.8 inch rear is?

  14. The '57-'59 Ford big car 9-inch rears have the very same 52¼" (bare) housing width as the '65/'66 Mustang rears.

    The 9-inch rears were also (optionally) available in the '75-'80 Granadas and Mercury Monarchs. These also had the 52¼" (bare) housing width. Some were drum brake equipped, and some had disc brakes --same rear end as the '77-'80 Lincoln Versailles.

    You can also put disc brakes on 9-inch rear end. This is a 9-inch (used to be drum brake equipped) rear I got from an '80 Mercury Monarch. I fabricated the brackets to mount '94-'04 Cobra rear discs onto the 9-inch Monarch housing. This rear end assembly will be going under my '68 notchback; http://www.ultrastang.com/images/2006/cobrabrakehosemount0243cf_2.jpg

  15. the 8.8 rear is slightly more efficient than a 9 inch but i'll take the 9 inch over the 8.8 anyday. i hate c-clips and i really like the dropout center section of the 9 inch. there is a reason why a very high percentage of racers use the 9 inch and that is durability and longevity and of course the plethora of available gear ratios.
  16. It costs the same to narrow either one. If you can get an Explorer 8.8 with Trac-loc, and 3.73's for a good price, that's a starting point. All the Explorer/Mountaineer and F & E150 8.8's have 31 spline axles. The Stang and Rangers are 28. It really comes down to which rear you can get easiest and cheaper. The Explorer/Mountaineer 8.8 came in three ratios and two brake configueations. Gear ratios were 3.08 (drums) 3.73 (discs) and 4.11 (these are the hardest to find but I don't know which brakes they had) At one local yard I went hunting for one and out of 6 rears, four had 3.08's with drums and two had 3.73/trac-loc and discs) I was looking for a 4.11 geared unit. Went to another yard and fell into an 81 Bronco 9 with 3.50's 31 splines and trac loc for $200. If you're going to narrow an 8.8, you may as well also convert it with 9" style bearing ends to eliminate the "C" clips, the only extra cost there is the bearing housings, axles cost the same for either style. I narrowed an Explorer 8.8 for my Ranger and total cost with 9" ends and Strange axles was about $800. Rear discs for an 8" or a Stang 9" ? look for 90's Crown Vic or a Marquis. from what I've heard it's all a bolt on swap.
  17. I had a 2001 ranger that I rebuilt after it was wrecked and the rear end housing tube was warped slightly. It is a 4.10 31 spline drum rear. The ranger was an edge...I thought about trying to use this in my 68 coupe but by the time I rebuild the brakes and straighten the tube I would probably be in more money than if I gt an 8.8 out of a Mustang...also I plan on running my car lowered and the offset pinion would make the drive shaft hit my floor...
  18. Wrong...
    The 8.8" is actually heavier than a 9"
    8.8" disc brakes will bolt to either small or Torino bearing 9" housings.
    You just have to get Vic discs for small, or Exploder discs for Torino.

    Do you have an 8" now? (5 lug)
    They are the same axles as a 28 spline 9"...
    Do what Ford (and Shelby) did in 65-66:
    Cut the axle tubes off your 8" housing center, then weld a 9" housing center in it's place.
    Now you have a small bearing, 28 spline 9" in the correct length and pinion angle to bolt right back into your car.
    This method is much cheaper than narrowing any rear and cutting the axles.
    Just make sure you use a common 9" housing for the center donor...
    There are 2 teirs of 9" housing values:
    Expensive and dirt cheap.
    Any narrow car housing is expensive.
    The rest are abundant and cheap (even free).

    After doing this mod, throw a set of Crown Vic 8.8" discs.
    Use a 28 spline chunk.
  19. There are a heck of a lot of threads on this subject