Update on my non functioning speedometer problem

Hi All,
I finally got to test a few things tonight and I no longer think I have a bad speedo cable or speedometer. I ran two tests tonight

1) Disconnected the speedo cable at both ends and had a helper site in the drivers seat with a clear view of the end of the cable that goes into the speedometer, while I attached a drill to the transmission end - I then started to slowly turn the transmission end of the cable and my helper reported the other end was also turning - it kept turning through various speeds and continual test as well - this indicated to me that my existing speedo cable was not broken as I thought

2) Test #2 - I reconnected the speedo cable to the back of the speedometer and left the tranny end connected to my drill. I then turned the drill at various speeds while my helper watched the speedo - the speedo needle moved to more mph as the drill was sped up and held stead when drill was held steady ( as possible) - this indicates to me that the speedo itself is working - needle was not jumping wildly or making any weird noises

These two tests taken together indicate to me that my cable and speedometer are not broken - This now suggests either the adapter the speedo cable hooks into, or the tranny itself - I have no idea how to test either one. I do see the adapter has a threaded fitting the same in size as the speedo cable and that the adapter can rotate freely about 20-40 degrees while securely fastened down. I notice also that there appears to be a slot in the adapter and some kind of key that looks like it might go in the slot - the key and bolt holding it were tight however as my next thought was maybe that key came loose

So , I need some suggestions here - I was thinking of taking off the adapter and taking it apart or buying a new one - but that is a wild guess at this point - I don't see this adapter for sale in any of the old truck vendor catalogs yet - How would I test it and anyone know where I might buy a new one if it is the culprit - I don't want to think of the other possibility here in my mind - something in the tranny housing ( speedometer gear) is not working or broken - she drives fine, shifts fine

Any help would be appreciated

Joe


Joe Finkelstine
Born and bred in Motown