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2000 GMC 2500 Pickup Question: Installed a rebuilt 4l80e tranny, speedometer doesn't work & shifts hard?

 

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wds, Melrose, NM, April 18, 2012, 13:35
 Rookie

speedometer work but doesn't show full speed and must feather gas to make shift. Tranny shop says loose connection, checked all connection still no work

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    Miles Auto Services (884 Answers) , Richmond, VA - (804) 885-4176
    milesauto April 18, 2012, 13:58
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     Master

    Vehical speed sensor and connections between it and PCM can cause this. Also if alternator starts putting out a/c voltage it can do this too. VSS is on the transmission or transfer case if its a 4X4.

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    wds, April 18, 2012, 14:37
     Rookie

    how do you check vss? I checked the connections and everything seems tight. I still have the old tranny, should I remove th speed sensor and install in rebuilt unit?

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    milesauto, April 18, 2012, 17:36
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     Master

    with a volt meter on a/c voltage scale or a lab scope. Faster the turn of out drive the more a/c voltage it puts out. With a lab scope it senda wave form that intencefies the faster shaft turns.

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