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53Rick · 06-27-2016, 10:25 PM

I have a '72 GMC 1/2-ton with a Turbo 400 transmission. Recently the speedometer stopped working. I checked cable connections to be sure they were tight. Just starting to troubleshoot it. Crawling underneath I noticed the cable is tight where it connects to the speedometer cable adapter. However I noticed there is some wiggle in the adapter and it rotates somewhere close to 180 degrees when I turn it. I don't know what this adapter does and before diagnosing further, I wanted to be sure that the adapter is supposed to turn freely. If so, I will move on. If not then any help on determining why it rotates would be appreciated. I have read the shop manual and the overhaul manual and can find nothing that speaks to the adapter. The adapter I am talking about is called an adapter in the manual and the speedometer cable connects to it at the transmission. Any assistance appreciated.

06-27-2016, 10:25 PM	#1
53Rick Registered User Join Date: Jul 2004 Location: Silverton OR Posts: 20	Speedometer Cable Adapter question I have a '72 GMC 1/2-ton with a Turbo 400 transmission. Recently the speedometer stopped working. I checked cable connections to be sure they were tight. Just starting to troubleshoot it. Crawling underneath I noticed the cable is tight where it connects to the speedometer cable adapter. However I noticed there is some wiggle in the adapter and it rotates somewhere close to 180 degrees when I turn it. I don't know what this adapter does and before diagnosing further, I wanted to be sure that the adapter is supposed to turn freely. If so, I will move on. If not then any help on determining why it rotates would be appreciated. I have read the shop manual and the overhaul manual and can find nothing that speaks to the adapter. The adapter I am talking about is called an adapter in the manual and the speedometer cable connects to it at the transmission. Any assistance appreciated.