86 gt speedometer is acting up

Discussion in 'Fox 5.0 Mustang Tech' started by 86sleeper5.0, Mar 27, 2009.

  1. 86sleeper5.0 New Member

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    I bought 86 5.0 recently. And it didn't take long before the trans went out. which i figured was gonna happen the guy i got it from was building the engine and rear end and neglecting the trans. Anyway i got a WC t5 from the local salvage yard and nothing is different except the speedo gear. The one that came out of the car was a whine color speedo gear and the one that came with the new trans is black. Now for the weird part. 0-30 my speedo is accurate after that it slowly slows down at 45 I'm doing 55 at 55 I'm doing 68. the guy at the salvage yard said the trans was for an 86 gt so i don't know where to start trying to get the speedo to read right. the rear gear is a 3.73 thanks for any advice
    86sleeper5.0, Mar 27, 2009
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  2. 93 LX Founding Member

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    93 LX, Mar 27, 2009
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  3. NIKwoaC Mustang Master

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    Actually I'm pretty sure the WC T-5 first appeared in the '85 Mustangs.

    But I agree, it sounds like a case of mismatched speedo gears. If you check out FRPP's website, you can download a PDF of their catalog. IIRC, there should be a speedo gear calculator in it, and it will point you in the right direction for which driven gear you need to buy.

    Linky:
    Ford Racing Performance Parts [Ford Racing Parts Catalogs]
    NIKwoaC, Mar 27, 2009
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  4. Strype Cuthbert catcher

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    If I could only remember what it came with :scratch:


    Hold on let me think...


    I put a red one in my old 86 t-5, and the one I pulled out was NOT maroon. Yellow or orange.
    Strype, Mar 27, 2009
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  5. 86sleeper5.0 New Member

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    can i try to put the maroon one in the new trans or would that be a disaster?
    86sleeper5.0, Mar 28, 2009
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  6. 93 LX Founding Member

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    You are Correct sir. I was thinking the Z T-5s didnt come out until late in the Mustang FOX time...

    From the Web Site: Modern Driveline - T5 History in Ford Mustangs with specifications for World class and non-World class T5's

    "1985, Ford introduced the World Class T-5 installed with 3.35 first gear set with a .68od behind the 5.OL."

    My mistake was made here.. "In 1993 Ford started offering a new service unit to the motorsport crowd. The "Z" spec T-5 (Ford part number 7003Z, also sometimes referred to as "World Class T-5". "
    93 LX, Mar 28, 2009
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