I own a 1996 Ford Windstar with 143,000 miles on it (trips to Alaska to work for summer and trips across the country). I replaced the alternator 8 months ago on the last drive down from AK…
I never know what speed I am going if I exceed 40mph - the needle flips around too much.
Lube or replace the cable from the trans to the speedometer.
There is no cable from the speedo to the trans. It was discontinued back when Moses crossed the Red Sea. OK, I’m exagerating.
I can’t tell you what the problem is but I have an 03 junkstar that the dealer has put 4 clusters in and the speedo still jumps. Not bad but it should not happen.
Yup, it’s more likely that this car has an electronic speed sensor which can have the same effect when it fails.