Has anyone rebuilt the transducer (the unit which the speedo cables, vacuum hoses and wire connect to under the hood). I know that they can be rebuild and my local AC-Delco parts store sells exchange rebuilt units for about $50. On a short interstate trip today, the factory cruise that I installed on the 70 conv started surging lightly, but constantly. At first I thought the carb wasn't getting good fuel pressure (kind of like a clogged fuel filter), but finally determined it was the cruise. When we got home I removed and disassembled the transducer, inspected, cleaned and reassembled it. Didn't find any obvious problems, but I didn't know what to look for either. It would be nice to locate a rebuild kit for these units. Any experience out there?

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Tom Parsons

Tom,
I have had some luck in making one good unit out of several used ones. They can be had for next to nothing at the bone yards and are pretty simple peices.


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Bill Koustenis
Advanced Automotive Machine
Waldorf Md

1971 Heavy Chevy - original owner
Team Chevelle #100

Tom,

I haven't rebuilt one yet, but have been told how by a retired GM mechanic I have in the family. I'm about to add CC to my 72 El Camino when the weather cools off here in Phoenix.

All you have to do it take it apart, clean up all the contacts and relube it. He told me there never was any parts available for these. They either replaced the unit or cleaned and relubed it. I've got one apart, and there is very few parts inside. Let me know how the rebuild goes.

Take Care,




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Jim Endrud - Gold #45
72 El Camino SS Clone
azonline.com/~jimmy (http://azonline.com/~jimmy)

Jimmy,
That's exactly what I discovered. Really nothing obvious to to repair/replace. So I just cleaned it up, lubed the shaft and put it back together. But it still surges.

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Tom Parsons

When I worked in GM dealers years ago, we would send the transducers out to Delco supported speedometer shops to have them rebuilt or recalibrated. You may want to check the cruise cable adjustment, the reservoir for vacuum leaks (it should hold vacuum unless the pedal vac switch is out of adjustment), and if the speedo is jumping at steady speed that can cause the surge. Also check the vacuum hoses for restrictions or leaks.

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Team Chevelle Gold #33
ACES Member #02913
Chevelle Club of Michigan
Livonia, Michigan

Tom is on the right track I think. It can only be a speedo cable problem or a vacuum problem. I think you should lube up the speedo cable, and check the vacuum operated servo for leaks. Let us know what you find, since I will be adding CC to my Elky very soon.

Good Luck,


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Jim Endrud - Gold #45
72 El Camino SS Clone
azonline.com/~jimmy (http://azonline.com/~jimmy)

[This message has been edited by jimmy (edited 09-05-99).]

We went to the store tonight and I noticed the speedo needle fluctuating. When I had the transducer apart and inspected everything closely, I noticed the gears for the drive and driven cable were in excellent shape. Also, a few months ago when I put all of this together, I lubed the cables good. Therefore, the last possible source is the plastic gear in the tranny. I will check that tomorrow for excess wear on the teeth.

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Tom Parsons