Sn95 Rear Axle Swap Questions

Discussion in 'Fox 5.0 Mustang Tech' started by fivespeedsteed, Jun 3, 2014.

  1. have a 90 gt, with 94-95 front 5 lug setup (gt/v6 calipers and hoses and all) and ranger rear axles and drums.

    my rear axle has 2.73 gears, the trac loc dosent work, and its got a bolt broken off in the housing for one of the cover bolts. id like the width to match the front, and im planning on doing a pan hard bar soon, so here is my idea.

    i only want 3.27 gears, and disc rear brakes, so can i go to a junk yard and find a 94-99 mustang gt and pull the rear axle (complete with hoses and calipers), brake booster, and master cyl and swap all that into my car?

    i have a set of 3.27 gears if it has 3.08s in there, and im not too concerned about doing cobra brakes right now.

    will the sn95 booster and mc work?

    it would get new rotors and pads, that goes without saying, and i already have the front sn95 stuff so i feel like the pedal effort would be right.

    i know ill need probably the prop. valve, 3-2 line conversion, one of those plugs, and an adapter fitting or whatever for the rear hard lines, but am i on the right track? do sn95 booster/mc's fit on foxes?

    does the v6 94-98 have a different booster and master cyl?
    #1 fivespeedsteed, Jun 3, 2014
    Last edited: Jun 3, 2014
  2. A 1994 - 1998 rear will bolt right in, it will be slightly wider do to the brakes but its no big deal.
  3. Your model will be a 94-95 Mustang GT or V6, so those are the parts you want to target
    For rear ends, ONLY 94-98. Do not get a 99+ rear as they are physically wider.

    You'll need to change the brake lines on the 96-98 rear to match the 94-95 Mustang line setup.
    Up front, 94-95 GT/V6 MC is the only one to consider here. Bore size is unique to the SN95 rear calipers and the front 66mm single piston calipers.

    Booster...1993 Cobra booster is a slightly easier install, but you can use a 94-95 booster or a 99-04 V6 booster. Do not use a 96-98 booster.

    Of course you'll need the typical 3-2 conversion, adjustable prop valve and the Sn95/fox hybrid e-brake parts (which are becoming hard to find)

    Later on, if you wanted to do Cobra front 13" brakes, you'll need to swap the think about if you want to do this now or don't care at all.

    Another option is to just swap on 99=04 GT 2-piston calipers. You can get these cheap, and will work with a 1993 Cobra 1" Master cylinder.
    You're call
    #3 Mustang5L5, Jun 4, 2014
    Last edited: Jun 4, 2014
  4. WHen you say the rear end from a 99' is wider by how much and i guess it's too late cause I bought one already
  5. The housing is 1.25" wider than an 86-98 housing. Add on the extra .75" each side for the disk brakes and you are looking at your rear wheels being pushed out 1.25" wider on each side out back. You would need some DEEP offset wheels ot avoid hitting the fenders

    Other issues are that the LCA mounting holes are a different size. 86-98 Cars use 12mm mounting bolts, while the 99+ cars use 14mm bolts. You'll need to adjust for this when mounting the axle up which can get a bit tricky
  6. You bought the one you shouldn't have bought.
  7. so a 94-95 mustang v6 has an 8.8 in it? did they mostly have 3.08 gears? im assuming the v6 axles didnt have trac locs?

    so 94-95 gt's and v6's all have the same rear axle, brakes, mc and booster?
  8. Well no. If you want an 8.8, you need to get it from a V8 car.

    But the axles, brakes, MC, booster, e-brake cables, rotors, etc are the same on a 94-95 V6 and GT
  9. for the front too? thats what i was figuring would be easiest since i already have 94-95 v6 front calipers and all that, i may as well match up the back. im not concerned with doing cobra stuff right now.

    does the booster work okay out of a 94-95 car? is a 93 cobra one going to be easier to install? which will give better pedal effort
  10. front brakes are the same between v6 and gt, so youre good to go there.

    as for cylinder and booster, ive got 93 cobra stuff for both, the 94/95 will work, or iirc the 96+ v6 will also work (the v8 stuff after that point is hydroboost, but im about 90% sure the v6 is still vac). i went with the 93 stuff just cause it was easier to make fit, the sn booster has one or two studs in a different place in the back. as far as performance, theyll ALL be able to lock the brakes with ease, so its kind of a washup, but the setup i have feels good and works well (93 cobra master/booster, 04 cobra fronts, drum rears). i know 5l5 has done all the math comparing all the cylinders and boosters to the different brake combos and how it should feel compared to stock, but i dont know how much subjective difference there is between them. just dont do a HUGE mismatch, and you should be good.
  11. Technically they are all the same booster. The difference is the stud pattern and thread pitch. The 1993 Cobra booster has the same thread pitch and stud pattern as the fox mustang, while the SN95 mustangs went over to a metric pitch and 1 of the studs is offset slightly. But they are basically the same mechanical booster. I even think some guys have stated that when they bought 1993 cobra boosters form parts store, what they got were SN95 boosters with the stud cut and rewelded in the different location.

    By easier install, i mean that you won't need to slot the firewall as much for that stud that is out of place on the Sn95 booster. I installed an SN95 booster in my car and it wasn't a huge deal. Just slotted the holes to the passenger side and it pivoted in. Didn't even need to touch the fender.

    Make sure if you grab a boneyard booster, grab one thats' clean looking. A lot of times the MC will leak at the rear and into the booster and degrade the rubber. Usually rust and peeling paint on the front of the booster under the MC is a sign to move onto the next one
    jrichker likes this.
  12. So if I get all the parts from the V6 car, master cylinder, rear diff, all front end parts that pertain to suspension and breaking, the whole car is mine to take whatever I want out of it. It has not yet been started to be pulled apart so I should take everything and leave the body engine and trans behind?
  13. the v6 rear is a 7.5 not an 8.8.

    how much work is involved in changing a 96-98 8.8 brake lines to work on a fox
  14. i found this write up too on whats needed to convert my axle to sn95 length stuff. does this sound right

    94-98 gt/v6 axle shafts
    94-98 gt/v6 rotors
    94-98 gt/v6 rear calipers
    94-98 gt/v6 soft hoses
    94-98 gt/v6 pads
    94-98 gt/v6 caliper brackets
    e brake cables for a 94-98 gt/v6
    center ebrake cable 94-98 gt/v6
    the adapters for hard to soft lines

    is that whats needed to make my rear axle the same as an sn axle? i have the gears i want to run, and was going to buy new calipers/rotors/pads/e brake cables and hoses anyways
  15. What do you mean? Which brake lines?

  16. Off a 99+ V6?

    Need to be specific because some of the parts are different. On a V6, the rear is a 7.5" so you don't want that. The brakes however are the same as the GT so you can pull those all apart and just swap it over to your current 8.8. If you take parts from a 99+ however, the axles are useless to you. Too long.

    The rest of your question all depends on what year car you are stripping
  17. Made some changes to the above list. The brakes are identical out back for all 94-04 GT's and V6. The only difference since the 99+ housing is wider, the axles were longer in 99+. SO if you put 99-04 axles in an 86-98 rear end...they would stick WAAAAY out and not work at all.

    As for the soft hoses, in 1996 Ford transitions to a 4-channel ABS system and started running all the brake lines on the body. So 1996+ rear hoses jump from body to the calipers. You want 94-95 rear hoses as they are mounted to the axle just like a fox car.

    As for the e-brake system, the only way to use SN95 cables will involve removing the cable guide system from an Sn95 and tack welding it to the fox.

    For direct bolt on E-brake, on a 1990, you want three aftermarket cables, M-2010-A and M-2809A cables

    2 of these

    1 of these

    It doesn't come with a nut, but IIRC it's 8mm. I double nutted mine with a washer
  18. Also, just to throw another idea out there...

    That kit is for rear cobra brakes. You would need 94-98 axles and some Cobra calipers (or modified GT/V6) to have rear 11.65" disk brakes.

    Piston size is the same as the GT.V6 and you can dial down the pressure with the adjustable prop valve to prevent lockup. Just a good way to get NEW parts for pretty cheap.

    E-brake and soft line connections would be the same as GT/V6.

    Here's the M-2300-K instructions to read through. This is for cobra brakes, but the idea is pretty much the same
  19. So that 2300m kit and calipers and axles is all id need? That have antimoans in it? Do they have a kit for the front too to go to cobra stuff?
  20. provided you're going to stick with sn95 axle lengths, yeah, thats all youll need, including antimoans. its the same parts as an sn cobra though, and the gt/v6 stuff uses the same calipers (cobra calipers just have thinner pads to account for the thicker rotor). its probably much cheaper to just grab em from a yard.

    the front calipers usually come with brackets, and bolt to the same place on the spindle, so theres really nothing extra to buy there, just calipers and rotors, which can also be found in kit form as just the fronts, or fronts and rears together (or at least used to be, in all the different cobra/bullit/mach colors too).