BMW Repair: Speedometer, rear muffler, senser

Question
Last few days, I have noticed that my bmw-1990-525i-has problem with the speedometer. It works some time and stops for some time. I dont know what might be a problem.

Help on this issue. Also, Trying to replace rear muffler.can you list the needed parts other then muffler.

Thanks,
Prakash


Answer
First, Ihave nothing to do with parts sales.Those sites just link to me for free advice.
The speedo on your car is electric, not mechanical, and can go out for a lot of reasons.
Does the odometer continue to work when the speedo stops?If so the head is bad.  
The senser in the trans could be bad or the wiring in between the two.  Being intermittent makes it hard to check.