Speed Sensor problems of the 2001 Nissan Altima

I have a 2001 Nissan Altima. At aprox 34,000 miles (car now has 42000) the instrument cluster would fail, the overdirve light would start flahing then overdrive would disengage. The instrument cluster and overdrive would come back on then minutes later the engine would start lurching causing the car to slow to 30 mph and eventually stop. The engine would still run but revving is choppy and lagged. After a few minutes or shutting the engine down and reststarting the engine the car would return to normal, but after a period of 10 minutes would repeat incident. Have taken to a dealer on 4 occasions, but mechanics cannot duplicate failure. Only one code has come back from the diagnostic p0500 (speed sensor failure) and the service engine light has only come on once. This issue has been re-occurring since April of 2003 and no repairs have been attempted due to the fact that mechanics cannot find nor duplicate problem. I have recorded 15 or more failures since April and 9 in the past 4 days.