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Thread: high HP rear end options

  1. #1

    Default high HP rear end options

    Hi everyone, got a question for y'all:

    I am probably pushing the limits of the stock rear in my 84 wagon. Only upgrades are 3.55 gears and a trac loc. Right now my wagon run the 1/4 mile deep into the 11's, makes an easy 700 hp and probably weighs more than when it rolled off the assembly line.

    I was thinking a minimum of 31 spline axles, carrier and posi plus I need axle retention and a 1350 pinion flange.

    I talked to my local fab guy and he said my rear has tapered tube ends so putting 9" housing ends for axle retention would narrow down my rear. Plus then I'd be looking for new brakes, unless mustang brakes will bolt up to the box axles, then those would work with the 9" housing ends designed for mustangs.

    I could look for a limo rear - sounds like that would be a bolt in affair then I'd just have to figure out the axle retention issue. are the 31 spline aero rears the same width?

    Thanks!
    1984 Mercury Colony Park Wagon - gone to the darkside. 5.3 LS Turbo Swap with 4L80E. 11.42 @ 121 so far, full weight, AC, no compromises!

  2. #2
    Wagon Addicted Tiggie's Avatar
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    4000lbs, 700 horse, and 11’s dang dude that’s impressive, even more so through the stock 8.8.

    My two cents: stud girdle the 8.8. You can get 31-spline axles made in the right length. And do the bolt on c-clip eliminators. Don’t mess the Uber rare limo rear unless one falls in your lap.

    I don’t think panthers went 31 spline until 04-05ish. Wider axles no good for you.
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  3. #3
    Beater gonna beat sly's Avatar
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    yeah... 31 spline was 05+ only. special order from Moser will get you 31 spline though. The 8.8 can handle the power, though a few mods are worth the time... welding the tubes to the pumpkin, diff girdle (cover with the bearing cap support), and the ADTR control arms to support that axle. You'll at least want to put energy suspension bushings in the stock arms and maybe even box the lower arms (outer). The C-Clip eliminators are actually frowned on in stock/street drag race classes. Not sure why. They do simplify maintenance and repair. 31 spline conversion should net you a safe margin to 950hp or so, with the added supporting mods mentioned here. Maybe even higher. I do know that Cleetus McFarland's CVPI (Neighbor) is still all stock rear axle with a supercharged GT500 modular under the hood pushing around that much HP out.

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  4. #4

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    Quote Originally Posted by sly View Post
    yeah... 31 spline was 05+ only. special order from Moser will get you 31 spline though. The 8.8 can handle the power, though a few mods are worth the time... welding the tubes to the pumpkin, diff girdle (cover with the bearing cap support), and the ADTR control arms to support that axle. You'll at least want to put energy suspension bushings in the stock arms and maybe even box the lower arms (outer). The C-Clip eliminators are actually frowned on in stock/street drag race classes. Not sure why. They do simplify maintenance and repair. 31 spline conversion should net you a safe margin to 950hp or so, with the added supporting mods mentioned here. Maybe even higher. I do know that Cleetus McFarland's CVPI (Neighbor) is still all stock rear axle with a supercharged GT500 modular under the hood pushing around that much HP out.
    That's good to know. I was thinking about a "budget" rear axle build and this list of parts would not be difficult or expensive. I would want some type of axle retention other than c clips so maybe just upgrading to rear disc brakes would work adding a little layer or safety. I wouldn't get the bigger axle bearings though. I'm not planning on launching super hard at the drags,no trans brake or anything but I would like some peace of mind.

    I also need to do a 1350 pinion flange since right now I'm running a 1350 to 1310 adapter since my driveshaft uses the 1350. The 1310 u joint is another stock weak point I'm sure.
    1984 Mercury Colony Park Wagon - gone to the darkside. 5.3 LS Turbo Swap with 4L80E. 11.42 @ 121 so far, full weight, AC, no compromises!

  5. #5
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    I'm almost positive my 1984 merc wagoo had a 8.5" under it. I swapped in a K-code 8.8 from a yard. It's in my barn, I'll look at the tag.

  6. #6

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    Quote Originally Posted by JeffBoudah View Post
    I'm almost positive my 1984 merc wagoo had a 8.5" under it. I swapped in a K-code 8.8 from a yard. It's in my barn, I'll look at the tag.
    Correct, Mine does too, but 8.8 parts will fit. From what I understand, the housings are the same just the size of the ring gear is different. I have 3.55 gears and posi from an 8.8 mustang rear and they work great and fit perfectly.
    1984 Mercury Colony Park Wagon - gone to the darkside. 5.3 LS Turbo Swap with 4L80E. 11.42 @ 121 so far, full weight, AC, no compromises!

  7. #7
    Hobbit
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    Check with Chris at ADTR. As I recall he put a 9 inch on the Rocket Couch.

  8. #8
    I'm an air-conditioned gypsy gadget73's Avatar
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    I was under the impression the 8.5 ended in 83, but whatever. They're effectively identical to the 8.8. Same carrier and housing, just 1/4" larger ring gear. You can stick an 8.8 gear set in an 8.5 housing. The traction lock in my black Mark VII actually came from an 82 8.5 car.

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  9. #9
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    drhill I suggest that you PM Pantera on what he would recomend on what gears to use for your aplacation he is quite knowegeable on that subject.

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