I noticed today that my speedometer is acting a bit erratic. It does fine up until 20mph, but then stays around 20mph until I hit 40mph, and then pops up to 40mph.

I'm guessing this is a problem with lubrication of the speedometer cable. I don't have a manual, but would I really need one for quick job like this?

If anyone can give me some pointers about how to do this, I'd be greatly appreciative.

Thanks in Advance.