speedometer failure

[jwpauler]

Someone please help, I am having to drive around without a speedometer! I changed out instrument clusters on my 1987 Ford F-150. I picked up a new one from a junk yard, they said that the truck was just wrecked and that there was nothing wrong with the speedo. I put that one in my pickup and everything worked fine, except for the speedometer. I took the truck to ford who said that the speedometer was failing. I replaced it with another one and it is still doing the same thing. I posted a message to this newsgroup earlier and got a few suggestions. I have tried them all and it still doesn't work. Tonight I pulled out the cluster, disconnected the speedometer cable from the transmission and removed the speeo wire. I cleaned the wire and lubed it up and put it back. I cleaned off the gear from the transmission (18 teeth) and I put my finger in the hole. The gear on the inside feels clean and is oiled. All of the teeth there feel fine. I put a little lube on the gear and put it back. I hooked up the cluster and drove it, it still does the same thing! To better explain the problem: When I drive down the road it does fine under 20 mph. It is a little jumpy, but isn't too bad. Then when you get above 30 it jumps way over. It is enough that when I accelarate to 45 it passes 45 and goes to 70. I know I am not going 75! Can someone please help? Do I need to replace that gear or do I need to replace the cable itself, could this head also be bad.. Is there something I am missing? PLEASE HELP!

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[spanky777will]

Sounds like the cable is bad. I think a gear comes with a new cable (not 100% sure)

[jwpauler]

I know this is going to sound stupid, but please bear with me. From what I can tell that speedometer wire is just a peice of metal... What exactly could fail with it? It just has to rotate, and when I turn it at the tranny it spins the speedometer.

-- jwp