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Discussion Starter #1
just wanted to get something straight about supercoupes
did they come with an 8.8 rearend or 7.5? and what kind of gears did they have? the halfshafts are stronger than an LX, correct? is it different for each year? i am wondering mostly about a 91 5 speed supercoupe.
well thanx guyz
 

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The Parts Guy
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They all came with 8.8"s. The 5-speeds had 2.73's, the 89-93 autos had 3.27's and the 94-95 autos had 3.31's. The 5-speed passenger side halfshaft is the largest factory halfshaft for MN12's.

If I'm incorrect on any of this, feel free to correct me. I'm pretty certain that my info is correct.

-Rod
 

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Are the halfshafts interchangeable, like, can I run two pass side halfshafts, on on duh the passenger side, and one on the driver side?
 

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Discussion Starter #5
well what about the n/a 3.8's
are they also 8.8?
 

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The Parts Guy
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92CougLS,

Yes, they are interchangeable from side to side.


Thundersteel,

I'm pretty sure that the 94-95 SC autos had 3.31's, not 3.27's.


rossf83+1,

The N/A 3.8's came standard with the 7.5", with the 8.8" as an option.


-Rod
 

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Discussion Starter #7
'preciate it
your the man
 

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Maybe it's both?

In the service manual, one place lists four different ratios (2.73, 3.08, 3.27, & 3.31), while elsewhere it lists only three (all but the 3.31).
 

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All 95 auto's came with 3.31's I believe. From what Jason Miller posted it sounds like some 94 auto's came with 3.27's and some with with 3.31's. I know for a fact my 94 auto came with 3.31's which is represented by axle code 9 on the vehicle certification label located on the driver side door piller. Actually Jason is the only 94 owner I know of with 3.27's as all others I've talked to about this have 3.31's. Any more 94 automatic owners with 3.27's?
 

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I have a 95 auto with 3.31's that I swapped for a t-lock 3.27's.
Everyone needs a t-lock and money for new rear tires.

I have heard there are some 3.27's stock though.
-Julian
 

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Everyone needs a t-lock and money for new rear tires.

I here you T-bird4vr. I also switched to a trac-lok differential in my 94 auto but for gears I went with 3.55's. Can you say smoke'm at will boy's and girl's??? :D
 

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Jimmy, are 3.55's the way to go, or would you say get the 73's? I couldn't make up my mind and was getting tired of 1 leggers so just rebuilt the t-lock and put it in. Diff was from an older auto.

-Julian
 

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Julian, for a 94 or 95 SC with the 4R70W transmission I believe 3.55's to be the best choice. For an 89-93 SC with an AOD transmission 3.73's seem to be the best choice. The transmission gear ratios from 1'st to 4’Th for the 4R70W are 2.84, 1.55, 1.00, and 070. For the AOD they are 2.40, 1.47, 1.00, and 0.67. With the lower 1'st and 2'nd gears of the 4R70W you will still have a higher final drive ratio with 3.55's than an AOD SC with 3.73's...especially 1'st gear which would be 10.082 final drive for the 4R70W vs. 8.952 final drive for the AOD to be exact. It's my opinion that 3.73's are TOO much gear for a 4R70W equipped (94/5) SC.
 

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Thanks Jimmy. I might have to make this a winter project. I should be able to borrow the tools to align the gears. Maybe.

-Julian
 

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Jason - what kind of gas mileage are you getting with 3.73's? Just curious if you have an idea since I'll be going with 3.73's in the future - just looking for an idea of what the gas mileage will be.

-Andy "Melon"
 

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The Parts Guy
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With my splitport tbird (which has 3.73's), I've been averaging 22-24 MPG on the highway (cruising around 75-80 MPH) as long as I take it easy on the throttle. Around town, I've been getting between 15-20 MPG. It really depends on how often you "get on it".

-Rod
 

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I think around town I lost about 1-2 mpg. But you're talking to a guy who likes to take off from the light quickly. On the highway I haven't noticed any change at all. I suppose if I kept it out of the boost around town I would get back thoes 1-2 mpg but, where's the fun in that. :zdevil:
 

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Thanks guys.. doesn't sound like my mpg will hurt too bad as long as I don't play with it. I'll be running with a 3.27 rear end for a while. Got a few other things I want to do first.

I just figure the 3.73's will be good enough for the track, but still give me decent gas mileage when I feel like driving my 'Bird around.

-Andy "Melon"
 
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