I did read the FAQ, but I have a really poor book reference to work from. Last night my speedometer started acting up -- the needle bouncing around the dial. I read in the faq that there is a speed sensor that could be cleaned. I got under the car and looked at the rear axle. I'm not sure what I am looking at. Is this sensor mounted on the outside where I can get at it, or is it located inside the differential,where I can't. In either case, could someone advise me on cleaning the sensor? Or if something else might be causing the problem.

Also, my ABS light comes on, usually (but not slways) after I hit a bump. I think I know what to do about that (clean the sensors on both front wheels, check the fuse on the ECU... I don't know where to find the back sensor. I have looked, but again, I'm guessing. I would SURE appreciate some guidance. The money is just not there to walk in to the Volvo shop and give them a generous blank check to fix it. If I can do it, it would a huge help, and I'm not afraid to try.
Thanks in advance.
Dean