speedo problems

[Buddy]

Jusy got my truck finally running right and took it for a little run, no windows, windsheild, seat, headlights grill etc... it was quite a sight lol. my problem is i noticed my speedometer was acting crazy. now I have nevr taken a trans out before this so I was wondering. Did i do something wrong with the cable? ijust pushed it in on the dash part, seem to go in fine there. I crawled underneath and noticed that it was a little loose there. never did nothing there yet. is there something i might have missed here. the speedo is just jumping all over the place, it jups up to 40 when i just move at a speed of like five, then when i get going it is jumping up to 140 down to 60 etc. I never had the truck going faster the 15 so I am not sure whats up? any ideas??? i should also metion it is a 700r4 with a 81 305,

[1980c10]

I would remove the cable and inspect it. It could be just that the cable is dry and needs to be lubed. It could also be pinched somewhere etc.

[bake74]

     On my 74, when I replaced my cable it jumped all over like you are describing.  All I needed to do was remove it out from the back of the gauge and reinstall it and it fixed the problem.  I think I had it in part way and not pushed all the way in until it latches with the metal clip.  Hope that helps..