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  1. #1

    Default 2.3 Turbo and 6.75 rear end ?

    Hi,

    I've found a 2.3L Turbo engine that could replace the very tired 2.3L in my notchback.

    But would the small 6.75 rear end be strong enough to handle 132hp ?

    Thanks !

  2. #2
    FEP Power Member ccurtin's Avatar
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    Quote Originally Posted by SuperDuty455 View Post
    Hi,

    I've found a 2.3L Turbo engine that could replace the very tired 2.3L in my notchback.

    But would the small 6.75 rear end be strong enough to handle 132hp ?

    Thanks !
    What year is your car? I thought 80+ were all 7.5's and they were stock in the SVO so you should be fine.
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  3. #3

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    For sure a 7.5.

  4. #4

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    Mine is a '79, and it has a 6.75. Same for my '79 V6 Ghia, which has a 6.75 as well. Both are 3.08 open.

  5. #5

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    I say run it 'till (if ever) it pops, then replace.

    As long as you don't have issue with the uncertainty.

    A large part of how any part "holds up" is how it is driven.

    Just planning to drive it on normal streets? Probably never have an issue.

    Plan on dropping the clutch at high RPM?

    Something will let go sooner or later....
    Last edited by great white; 12-08-2016 at 02:15 PM.

  6. #6

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    I never heard of a 6.5........thought it was 7.5 and 8.8. Huh........thanks for the lesson.

  7. #7

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    Allright, it won't be raced or driven hard. But a bit more power easily is always good. But the guy wants 600€ for the engine, not sure it's a good deal. I'd rather try to find a later SVO/Turbo Thunderbird engine for that price.

    The 6.75 is easy to spot as it has an octogonal shape with 8 bolts :

  8. #8
    FEP Power Member 81coupe's Avatar
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    I wouldn't trust it much. I've Popped a few of them in the past. It didn't take much to do it either. The 6.75 was in 79-81, 2.3L, NA Foxes I believe. The Car I have now, 81 mustang was originally 2.3L, NA, 88HP and came with the 6.75 Rear axle Housing.
    1981 Mustang Coupe: Rebuilt 91/306, Ported E7's, TF Spring kit, E-303 Cam, RPM Intake, Eddy 1406 Carb, FMS Dual Roller Timing set, March UD pulleys, Summit LT Headers, Summit 2-1/2" Chambered Mufflers w/ 2-1/2" FlowTech H-Pipe/ Flowtubes & 2-1/2" LMR SS Tailpipes. C4 trans with 8.8/ 2.73 Rear.

  9. #9

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    I would run it until it lets go, and when it goes you can say I saw that coming rather than planning on it living and being bummed when she goes. But who knows it might survive more than you think. I'm running my 80 with the 7.5 and it's been thru 5k+ launches on the street and the track on the bottle, and now my heavily modified turbo motor. I told myself years ago when it goes I'll upgrade. Even have done some clutch dumps in reverse which is probably a bad idea. I know people with 8.8s who have asked a lot less from them and they blow. if you have access to one switch it out and get a better gear ratio if the funds or availablity isn't there than run it and see what happens. I probably just jinxed myself by saying that!
    80 Capri built 5.0 single turbo manual trans
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  10. #10
    FEP Power Member 81coupe's Avatar
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    Quote Originally Posted by 80Merccapri View Post
    I would run it until it lets go, and when it goes you can say I saw that coming rather than planning on it living and being bummed when she goes. But who knows it might survive more than you think. I'm running my 80 with the 7.5 and it's been thru 5k+ launches on the street and the track on the bottle, and now my heavily modified turbo motor. I told myself years ago when it goes I'll upgrade. Even have done some clutch dumps in reverse which is probably a bad idea. I know people with 8.8s who have asked a lot less from them and they blow. if you have access to one switch it out and get a better gear ratio if the funds or availablity isn't there than run it and see what happens. I probably just jinxed myself by saying that!
    I do Agree. Run it until she goes boom, or upgrade Now if you can. Either way works. The main thing that will pop is Torque. Drive easy and it might live awhile. But then again the last one it popped was a 2.3L/ c3 combo simply backing out of the Driveway one Morning.

    IMO, Leave it there for now, and start saving up for a an 8.8 Housing for the future.
    1981 Mustang Coupe: Rebuilt 91/306, Ported E7's, TF Spring kit, E-303 Cam, RPM Intake, Eddy 1406 Carb, FMS Dual Roller Timing set, March UD pulleys, Summit LT Headers, Summit 2-1/2" Chambered Mufflers w/ 2-1/2" FlowTech H-Pipe/ Flowtubes & 2-1/2" LMR SS Tailpipes. C4 trans with 8.8/ 2.73 Rear.

  11. #11

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    OMG, just signed up here. I thought I was the only one in the world that had a leftover 6.75 in Mustang axle, from an 81 coupe. I broke one in a Mustang 2 back in 75. Just fixed it and went on. My 82 hatch has run high 12s with 7.5 in axles. They are lighter than 8.8 in units.

  12. #12
    FEP Super Member xctasy's Avatar
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    Quote Originally Posted by Oldrd View Post
    OMG, just signed up here. I thought I was the only one in the world that had a leftover 6.75 in Mustang axle, from an 81 coupe. I broke one in a Mustang 2 back in 75. Just fixed it and went on. My 82 hatch has run high 12s with 7.5 in axles. They are lighter than 8.8 in units.



    Not always octagonal... that was the early short pininion Pinto version....all 6.7 Sterling axleed Foxes had this. It's very small and square looking. A quick look at the square cover will be the easiest way to identify the 6.75.


    Its tag code is 6.7S, NOT 6.75, but its a 6.75 inch size for everyting and, IIRC maybee 6.875 for the 3.45 in the base model 2 liter poverty pack 1983-1988 Rangers. Could have been a rounding thing and they were all 6.75... who knows?

    Quote Originally Posted by 80 Capri View Post
    Have always assumed my '80 Capri RS had a 7.5 rear. Well, was crawling around under the back of the car, and this is definitely not a 7.5 or 8.8. I'm doing a 5.0/5 speed swap on the car and wasn't planning on swapping the rear immediately. Will this hold up for any amount of time behind a 5.0?





    Quote Originally Posted by xctasy View Post
    ......





    http://vb.foureyedpride.com/showthre...ock-diff-Gears

    This is a carefully edited repeat.

    Foxes with 6.7 Sterling were only 2.73, 3.08, 3.45.

    Rangers were 3.08, 3.45.

    6.7 Sterling Mustang II's were 2.73, 3.18, 3.27, 3.40, 3.55.

    6.7 Sterling Pinto's, not sure, probably same.

    Info I have is that the diff centre section was all the same from 1974 to 1988, when the last Ranger 2.0 was made with it.

    The actual 2.73 ratio came out in 1977 in the Mustang II 2.8 V6. Then a 3.27 ratio came out in 1978 on 2.8 V6's.

    No 6.7 diff ever got Limited Slip diffs

    Common early 1974 on Mustang II tags for those were

    WGF-H 3.40:1 6 3/4 C2 Integral
    WGF-K 3.40:1 6 3/4 C2 Integral
    WGF-M 3.55:1 6 3/4 C2 Integral
    WFZ-B 3.55:1 6 3/4 C2 Integral

    From 1977
    WGF-AJ 2.73:1 6 3/4 C2 Integral
    WGF-K1 3.18:1 6 3/4 C2 Integral
    WGF-U1 3.18:1 6 3/4 C2 Integral
    WGF-AA 3.18:1 6 3/4 C2 Integral

    From 1978
    WGF-AJ 3.27:1 6 3/4 C2 Integral

    See http://www.mustangii.org/decoder/axle/

    See http://i1215.photobucket.com/albums/...6/IMG_6984.jpg.

    On my 6.7 Sterling plant corporate diff, the code was:-

    WGG-C 0G24
    2 73 6 7 S258C

    WGG-C OG24
    2 73 6 7 S258C

    Std for a ‘79-‘82 Open 6.75” diff with a 2.73:1 ratio.

    Brown is Fords code for the ratio
    Red is the crown wheel diameter
    Blue is the Plant.

    All 6.7 (6.75, 6.875", but called 6.7 on the tag, but also 6.5, 6 3/4 in on line literature) and 7.5"s are Sterling built Salisbury integral carrier diffs.

    A generic 7.5 would be

    WFC-BY 4F13
    3 08A 7 5 S27IF


    If its limited slip, its 7.5 V8 or one of the Turbo LSD 7.5" from 1981 to 1984.


    Not everything 3.3 had a 7.5" diff/C4 combo there, 6.7/C3 was very common.

    The numbers are simple for the Sterling plant made 6.7 diffs, very common.

    Based on pinion seal part number, I think the US 6.75" diff came out in 1957, but was used in early XK 2000 Falcons (1960 year), then got replaced when early round bodies went to short pinion 7.0" diffs, then long pinion 7.25" diffs. The 6.75" lookes quite different even though it has 8 bolts. The diff then appeared to continue as the weedy short pinion 6.75" diff used in 23 spline form in 1971 to 1973 Pintos.

    The Fox 6.7 axle was based on the upgraded long pinion, big bearing and 24 spline item from the 1974-1978 PintoMustang II's, and the 1974 to 1980 Pinto/Bobcats.

    The ratio choices themeslves had been expanded to suit V6's, so the 2.73 gear I have in my 1981 first came out in 1977 in those leaf sprung diffs used in 2.8's. As I've said, it looks ilke Each emissions package required a certified diff ratio, so it was cheeper for Ford to tool up for a 2.73:1 ratio in the weedy 6.7 " diff than add a 2.73 ratio to the 8" diff. Part of the confusion with Ford diffs is that the 6.7, 7.5 and 8.8 are integral carrier diffs, with the same interchangable axles in the 7.5 and 8.8, and most people assume if its a Fox six, the diff in it will -be a 7.5 incher.

    The other point, is the 2.73, 3.08, 3.27 and 3.45, although proven to be inagural 6.7" ratios, they are 7.5 and 8.8 inch diff ratios too because cost of CAFE/EPA/FMVS certification ment they had to use the same ratio, despite the diff type. That's why the C3, C4 , 6.7 or 7.5" diff, transmissions and grey low mount or blue high mount 3.3 I6 engines where inserted willy nilly on the line...it cost Ford nothing, because each combo individually and as a package had 49 States certification.

    90% of the Fox I6's were 2.73. 2.47 was 7.5" only, on i6's and some V8's.

    A lot of the Fox 2.3's had the 6.7" in 3.08 or 3.45 ratio.


    If 3.3, and SROD or T4 four speed I6, they were 3.08 or 2.47. Again, it was listed in the brochure as 2.49, but that was with the SROD 0.80 overdrive fourth ratio applied. Just Ford being especially technically CORRECT!. T4's had 2.47 only, and were all 7.5". So far as I can tell...

    83-88 Ranger axle codes were 72 and 74 respectively in 3.08 and 3.45, the only easy way to find later good racier axle ratios for 6.7" diff parts was the entirely forgettable 80 hp to 73hp 1984-1988 2.0 liter base model 1-bbl and for a time, 2-bbl 2.0 Lima engine.

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