1970 CST/10 Speedometer / Transducer Question

[rmawyer]

Working on speedometer that never worked (needle not moving). Got new transducer for eventual restore of cruise control. Bypassed transducer and hooked new speedometer cable directly to transmission. Good news speedometer working but bad news it is showing twice the speed (40 MPH displays around 80 MPH, etc.). Does the transducer have anything to do with the double speed? Do I need to hook speedometer to transducer to transmission to reduce the speed or am I in a transmission gear replacement state? As always thanks for assistance. Bob

[gmc684x4]

Can you show a picture of what you are calling a transducer ?

[rmawyer]

Originally Posted by gmc684x4

Can you show a picture of what you are calling a transducer ?

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[rmawyer]

Originally Posted by rmawyer

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Volunteering away from home today so no pic until later. Transducer is small part that sits on inner fender. It has in and out ports for speedo cable from speedometer to transmission. Used for early cruise control. Rare for 1970.
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[rmawyer]

Sorry I took this long to get back with results. An experienced transmission guy (40+ years) said I had a rare 375 (not 350) turbo transmission and it was geared for heavy duty, so it needed an external speedometer gear reducer that takes the speedometer cable as input and then the reducer device attaches to the transmission. I ordered the device from PATC out of Louisiana and it corrected the problem. The transducer for the cruise control had nothing to do with the incorrect / double speedometer reading. Thanks.