[53Rick]

I did a little more diagnosis. Disconnected the speedometer cable at the transmission. Rotating the cable by hand moves the needle on the speedometer, so looks like the cable is fine. I removed the adapter (by the way it is a Stewart-Warner part 666F P 4 which is probably a ratio adapter). Turning the end of the pin on this adapter turns everything freely, so it appears to be functioning properly. I then jacked up the rear end and put the truck in drive. With the cable and adapter removed, I watched the end of the plastic speedometer gear and it does not turn with the drive shaft turning. My assumption is the plastic speedometer gear needs to be replaced which is really frustrating since it was replaced about 2 years ago when I had the transmission overhauled. This is a turbo 400 transmission and I have a spare speedometer gear that I bought when I bought the last one that needed to be replaced (43 teeth). It looks like I need a seal for it though. Does anyone know if a TH400 has any retaining clip inside that I will also need to order? And, most important, am I correct in assuming that with the drive shaft turning, the plastic speedometer gear should be turning? Seems like a no-brainer, but I just want to be certain.