I have a 2002 Mazda Protege5 (auto trans, 80k) that will occasionally make a sudden downshift at approx 60mph. The car will lurch, the speedometer briefly goes to zero (while the car is maintaing speed) and then within less than 5 seconds, the speedometer (dial type) will return to proper speed reading and car will upshift back to proper gear. This seems to happen around 60 mph and also occasionally happens on highways as the car begins to go on a downslope while maintaining highway speed. This happens frequently but not on every trip. When first happened, took to shop, they found AT fluid very dark and flushed and replaced AT fluid and filter. Problem not eliminated. Suggestions as to cause and likely cost would be appreciated. Thanks!
I don’t know what kind of shop this was - but I suspect it wasn’t a transmission shop. I’m not saying that the fluid/filter service wasn’t needed (I’m sure it was), but this kind of problem is not going to be addressed by fluid service.
Is your check engine light on?
You have a transmission “control” system problem. Coupled with the info about the speedometer I’d say it may be speed sensor related. You want to take it to a local, independent transmission shop - not a national chain & not a general repair shop - a local business with a decent reputation that specializes in transmission.
Describe the symptoms to them. They can scan it for errors, drive it with a scanner on it, etc.
Scan the computer for any codes first. Post here the code/s and we can help you further.