My '90 Grand Voyager just gave me its periodic transmission refill notice - 3rd gear lockout. Current mileage is around 148K, with 13,000 miles and 34 months since the last flush, with ATF+4.
A flashing light would be so much better than this method of communication, since it always results in an awkward moment on a high-speed roadway. And finding out what the specific condition is requires a visit to a dealership, one of which charged me for over an hour of shop time the last time I was curious enough to investigate.
Having looked through the volumes of communication on these early transmissions, I'm still not sure what the recommended service interval would be for fluid. Haynes says two years or 30K miles. I've seen 15K from more than one source. Driving this van about 5-6 K per year, I know that it doesn't leak, and that currently the fluid looks pretty clear. So, I'm wondering what the recommendation would be, and while we're at it, how do you flash one of these TCM's ?