97 Taurus Transmission / Speedometer relationship
Our Taurus has 78K miles on it. Tranny was replaced in 99 under warranty, so we are about 7 years and 50K with this one.
Lately weird things started to happen: when we start driving the speedometer is stuck in zero speed, the RPM goes up to around 2500-3000 without changing gear. Normally, at around 2500 when you accelerate hard the gear would change from 1st to 2nd.
In this situation, we need to either keep pushing over 3000 RPM, or let the accelerator go, which is when we feel some kind of a kick, the gear is changed from 1st to 2nd, and the speedometer needle is either remain stuck OR jump to whatever the speed is (25-30 mph).
I believe that the speedometer is indeed connected to the tranny, but what I would like to know is - what is the relationship between the two? Assuming there is a problem with the tranny that prevent the smooth change of gears, why does it effect the speedometer?
Aside of that, any idea of what may cause this problem?
Also, it doesn't happen all the time...once every now and then.
Other two pieces of info: there are no leaks from the transmission and fluid level is good (full). And also, nothing happens during cruise, it is just during start from Stop to movement of the car.