81 Silverado- Keeps blowing speedometer Transducers

[Mark97213]

Greetings all. Looking for some advice on why I might keep blowing speedometer transducers. I've gone through two replacements and although they work fine for about 30 minutes, they eventually just stop and the speedometer fails. Any idea what would cause the transducers' to keep failing? Rebuilt transmission with new speedometer plastic gear in transmission. I'm at a loss.

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[C10MixMaster]

well there are only two parts that could cause a cruise transducer to fail like that the speedometer or upper cable. Are you sure the transducers are actually failing? If so i would lean towards an upper cable needing oil or replacement. or did the upper cable come loose from the speedometer? Since you played with the gears in the tranny i would not write of the possibility cable or gear problem there to.

 

[Preston]

Welcome from Virginia to GMSB
I’m sure you (we) will be able to find a solution to your problem

 

[Charlie]

 

[Mark97213]

well there are only two parts that could cause a cruise transducer to fail like that the speedometer or upper cable. Are you sure the transducers are actually failing? If so i would lean towards an upper cable needing oil or replacement. or did the upper cable come loose from the speedometer? Since you played with the gears in the tranny i would not write of the possibility cable or gear problem there to.

The cables seem to turn fine but I can't imagine any binding issues since they work fine for 30 minutes or so. Could there be a bind in them that's subtle, causing them to slowly burn up the transducer? Doesn't seem likely.

 

[C10MixMaster]

The cables seem to turn fine but I can't imagine any binding issues since they work fine for 30 minutes or so. Could there be a bind in them that's subtle, causing them to slowly burn up the transducer? Doesn't seem likely.

if the transducer if failing the only thing i can see is something binding. since you have eliminated the "likely" now we have to consider the unlikely. remember that cable is spinning 1000 rpm at 60 mph. so a little friction could be a lot at speed. Have you ever seen a speedometer read steady at low speed and jump around at high speed that usually a binding cable. the other possibility is bad parts back to back. i have put in three alternators back to back two were bad rite out of the box! oil is a lot cheaper than a transducer thats were i would start. hope this helps

 

[Mark97213]

if the transducer if failing the only thing i can see is something binding. since you have eliminated the "likely" now we have to consider the unlikely. remember that cable is spinning 1000 rpm at 60 mph. so a little friction could be a lot at speed. Have you ever seen a speedometer read steady at low speed and jump around at high speed that usually a binding cable. the other possibility is bad parts back to back. i have put in three alternators back to back two were bad rite out of the box! oil is a lot cheaper than a transducer thats were i would start. hope this helps

Thanks for that, I think you may be right. The speedometer worked fine for around 30-45 minutes but then it starts getting erratic and then it fails. When it does, you can hear noise from the transducer which led me to believe I just simply bought a poor remanufactured transducer. So I bought a second one, from a different supplier and the same, 30 minute use, it failed as well. Seems unlikely to get two bad transducers from different suppliers. I'm thinking maybe I should just replace the upper and lower speedo cables. Probably unlikely but could any of the electrical connections be causing them to burn up? I suppose there could be some binding in the speedo itself, no?

 

[C10MixMaster]

Thanks for that, I think you may be right. The speedometer worked fine for around 30-45 minutes but then it starts getting erratic and then it fails. When it does, you can hear noise from the transducer which led me to believe I just simply bought a poor remanufactured transducer. So I bought a second one, from a different supplier and the same, 30 minute use, it failed as well. Seems unlikely to get two bad transducers from different suppliers. I'm thinking maybe I should just replace the upper and lower speedo cables. Probably unlikely but could any of the electrical connections be causing them to burn up? I suppose there could be some binding in the speedo itself, no?

the speedo binding is less likely but not impossible. The ones i have seen fail made a screeching scraping noise. i would put a drop or two of light weight oil or atf on the rear bushing just in case.

 

[Mark97213]

I'm afraid to buy a third transducer at $100 and have the same result. I guess if one cable turns freely but not the other as freely, seems like that could cause the transducer to burn up. Just a guess. I think I may just buy new upper and lower speedo cables to rule them out. Just seems odd.