speedo

my 87 bronco II speedo likes to bounce around ten to fifteen miles an hour. is it the sending unit gear thing in the trans or could it be in the dash. also the cruise works the same way. It will maintain speed but then it slows until the speedo catches up and then revs up again. are these two things linked?

I can't tell you exactly what's wrong man, but replacing the speedometer gear in the transmission is cheap and easy. It was on my 1990 Fullsize. I am not sure how difficult the cable would be to replace if replacing the gear didn't fix it. But, both are cheap and having an older vehicle anyways, it might be worth replacing them and seeing if that fixed your problem.