Changing old trans fluid

[milford2339]

My '98 Windstar has ~130,000 miles on it and I don't think it has ever been changed (I'm 2nd owner). We just started having this problem, hard shifts into second, sometimes won't shift to 2nd unless done manually then back to drive, and the speedometer sometimes drops out. I know a bit about transmissions since my company builds machines that test them at the end of the assembly lines but I'm not sure what to do here. What about using one of the pumps that will suck up out of the dip stick and just replace a little of the fluid at a time, say 1 pint a day? Since this would gradually replace the fluid, less slippage should occur. What do you think? What about replacing some with an additive that would help clean the fluid. Or should I just have the filter replaced and reuse the old fluid? As far as the speedometer dropping out, I'm thinking of having the speed sensor replaced. Thanks for any help.

[sahib]

Why don't you wait until you've changed the speed sensor before changing fluid. I believe that sensor relays information to the "brain box" which in turn tells the transmission what to do. Seems like most posts I've seen here from presumed knowledgable people say to leave the fluid if it hasn't been changed in 70k miles. Your call though, you are the owner.

[rodeo02]

If she's shifting fine now, pump out what you can thu the dipstick tube (about 4qts), which is about half the tranny's capacity, keep an eye on the shift quality & performance of the unit for awhile. Maybe go a thousand miles or so & do another pump out & refill. If she's holding strong at that point, you *could* do a pan drop & filter change just to get a feel for the condition of the unit, plus that will clean the ATF futher by replacing more ATF.
G/luck
Joel