We have a 1990 Toyota Corolla, About a month ago the speedometer suddenly started to work erratically. As we were driving it would regester either 0mph, or shoot up to over 60mph no matter how fast we drove the car. The odometer, and the milage counter continue to be working fine. I think that a gear in the speedometer is slipping, and I could repair it if I knew how to get access to it. What is the process to remove the speedometer? I have a Haynes Repair Manual, but it does not cover this issue. Thank you.