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post #1 of 7 (permalink) Old 11-10-2010, 09:12 AM Thread Starter
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posi rear

like to put in a posi rear on my 1992 thunderbird. has an 8.8 rear. The car has a 5.0 ho engine. What gear ratio should I get? How hard is it to put in. I brough the car new did not change anything. Any way You can get instructionson on how to install?
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post #2 of 7 (permalink) Old 11-10-2010, 12:05 PM
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Here's the tech articles. This has been discussed hundreds of times. General concensus seems to be 3:73 for all round usage.


95 Thunderbird LX 4.6
K&N cold air intake. True 2 1/4" duals, Xenon GFX. 3:55 Trac loc. Beefier trans, 2800 stall convertor, MkV111 aluminum driveshaft.
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post #3 of 7 (permalink) Old 11-10-2010, 12:23 PM
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Never tried putting a GM rearend in a bird before. This should prove interesting.

But, if what you meant was a traction-loc, then yes, follow the link above for your info. For gears I would say at least 3.73's, maybe even 4.10's. These cars a heavy and having good gears and a higher stall TC help get them moving.


These are highly engineered precision vehicles, the first step in diagnosing the problem is to strike the suspected offending part sharply and repeatedly with a blunt object, then re-test.
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post #4 of 7 (permalink) Old 11-10-2010, 12:36 PM
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4.10s? It all depends on what the dood wants to do with his car. If it's a daily driver, I would most likely not put in 4.10s. I'd probably go with 3.55s.

Since the car's stock and unless you plan on changing out the converter, I probably wouldn't put in 4.10s. Why have such a low stall converter and a 4.10 gear ratio?

89 Cougar XR-7...slightly modded, 240 rwhp / 340 rwtq, Best time as of 4/22/12 = 13.11 @ 103.82, 1.78 60'
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post #5 of 7 (permalink) Old 11-10-2010, 01:02 PM
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don't fear the gear.....I would say these cars need 4.10's at a minimum....

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post #6 of 7 (permalink) Old 11-10-2010, 03:22 PM
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post #7 of 7 (permalink) Old 11-10-2010, 04:08 PM
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I went from a 3.08 open to a 3.27 TL and now I'd say at least 3.73 or else you'll end up wanting more.

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