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Thread: 7.5 trac lock question

  1. #1
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    Default 7.5 trac lock question

    My oldest sons 88 sport bird has an aod & 7.5 in 2:73 rear trac lock rear.

    He is in discussion with an 87 stang owner that has a 5 speed & 7.5in 3:73 track lock rear.

    the stang owner wants to go AOD with a fuel economy rear gear.

    My son wants to make his bird a 5spd and move to 3:73


    question
    can both parties simply trade rear end internal rotating parts?,,,,


    the total plan here is they trade transmissions & rear gear internals.

    what we dont have for the bird is pedals..gotta research if stang pedals go into ours or not.

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    Last I was aware, an 87 Mustang with a 5.0 would have an 8.8 rear end. Maybe some research to verify. removing and installing a pinion gear is sort of an ordeal, and setup is extremely sensitive to proper pinion depth and ring gear backspacing. I'm an ASE Master, and even I don't want to do it. It's a pain in the ass, and I can count on one hand how many I've ever set up. I don't own the measuring tools, anytime I did one the tools for it belonged to the shop.
    I'm not sure I'd put the time and money into a 7.5 that you're probably still going to break eventually (assuming mods and power adders). Go 8.8
    1988 Thunderbird 5.0
    GT40P, TFS-1, KB domes, 30#, MAF conversion, Explorer GT40 Upper/Lower, Smog delete, Wide Ratio AOD Mod, Unlocked Speedo, 3G Charging System Upgrade, Hi-Torque Mini Starter, 3.73 LSD, BBK 1 5/8 unequal headers, H-Pipe.

    88 Thunderbird/Cougar EVTM
    (Thanks to Trinom for hosting)

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    Stang pedals work fine....I have 88 mustang pedals in 87 TC.

    I may be mistaken but the rear in the Stang should be an 8.8 unless it's a 4cyl which would not be a trac-lock unit. If it is truly a 7.5 track-loc yes you could swap internals but it likely be easier to swap the whole rear over. Personally.....I would look for an 8.8 rear.

    John

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    My understanding is the Stang pedals fit fine. I would also agree, I think it would be easier to swap the whole rear ends.
    Mike

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    Quote Originally Posted by TheFoeYouKnow View Post
    I'm not sure I'd put the time and money into a 7.5 that you're probably still going to break eventually (assuming mods and power adders). Go 8.8
    +1. I broke the crap out of the 3.73 geared 7.5" rear in my car. Spun the pinion bearing causing the pinion gear to move back and forth, banging off the carrier. Caused a hell of a noise/vibration. Went with a 3.73 geared 88 XR7 8.8" as a replacement. See below for noise

    https://www.youtube.com/watch?v=4xzkctodX0E
    '88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, Edelbrock 70mm TB, 76mm C&L MAF, 30lb injectors, 2.5" exhaust, AOD with 2800 PI converter, 8.8 with 3.73 gears, 31 spline Traction-Lok, 31 spline Moser axles, 04 Cobra front arms, Maximum Motorsports extreme duty rear arms, subframes.
    '11 Focus, '12 Mustang 3.7, '17 Accord EX-L V6

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    Only 7.5 rear with 3.73 gears I know of is behind a 2.3 n/a stang. Aid wouldn't swap.

    To swap the rear, I'd swap the whole rear end then swap the brakes /axles over. Otherwise you would have to get new crush slaves and reset both rear ends.
    Quote Originally Posted by jcassity
    I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
    Hooligans!
    1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
    1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
    1986 cougar.
    lilsammywasapunkrocker@yahoo.com

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    Quote Originally Posted by Haystack View Post
    Only 7.5 rear with 3.73 gears I know of is behind a 2.3 n/a stang. Aid wouldn't swap.

    To swap the rear, I'd swap the whole rear end then swap the brakes /axles over. Otherwise you would have to get new crush slaves and reset both rear ends.
    Agreed, all 5.0 Stangs from '86 used the 8.8" rear... From factory lowest ratio 8.8" was 3.27 and those were automatic only...

    I junked a '89 Stang half motor that had the 7.5" 3.73...






    My other rides (that actually do run & drive)

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    Find you a V8 '94-'98 Stang, do a full 5 lug, complete rear swap, AND gain discs. More work upfront, but......

    Your other 8.8 option with deeper gears is a TC rear. Still disc, gonna be the same work to convert to rear discs for the car, to me the downside is 4 lug. So much more of a selection of wheels with 5 lug rather than 4. The one plus is that if the TC rear is from a stick car, it's 3.55 and if it's from an auto TC, you'll have a 3.73.

    Myself, I'd find a wrecked '95-95 V8 Stang, pirate all the suspension shit, rebuild as needed and pop in. The pedals from any stick Stang (Fox, SN95 up to '99) will work, though there's a couple minor differences with regards to 2.3 vs 5.0 pedals. Both will work however.

    Whatever you do, pay attention to clutch cables..there's threads here that spell out which ones are junk, and which ones are better. I think Lou had some issues a time or two, IIRC.
    '87 Mustang notch; 5 lug, PBR calipers, 3.55 gears, SFC's, mild 5.0 with '40P's, Cobra intake, E cam, BBK headers and X pipe, Flowmaster exhaust.
    "still slower than your grandma's scooter"..

  9. #9
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    We are already 5 lug swapped on Mason's 88bird and rear disc with upgraded front disc

    not sure what motor is in the stang we are talking about but,, the cover tag says 3 73 and both rear wheels off the ground turn one the other turns the same direction... and its a 7.5.

    I am going to likely talk him out of it though,, he has some dcent motor mods and likley just enough to break the rear when he plays around.

    i can imagine he might enjoy 3 73 a little too much and break it... i can also respect the advice,, i knew 8.8 would be better but they are not easy to find around here.


    he lives in charlottsville va so its not like i can help unless he comes over here to home which is where the work would be done.

    thanks!

  10. #10
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    If he's not drag racing at a 1/4 mile track the 7.5 should last street driving. I broke mine after a couple violent track launches.
    '88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, Edelbrock 70mm TB, 76mm C&L MAF, 30lb injectors, 2.5" exhaust, AOD with 2800 PI converter, 8.8 with 3.73 gears, 31 spline Traction-Lok, 31 spline Moser axles, 04 Cobra front arms, Maximum Motorsports extreme duty rear arms, subframes.
    '11 Focus, '12 Mustang 3.7, '17 Accord EX-L V6

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