Transmission Acting Up and Terrible City MPG

[MrCreosote]

I had the trans replaced in my 2000 and the first thing I noticed that the transmission was very aggressive upshifting and locking-up so that engine rpm was kept low and loaded.

Now the transmission has lost this characteristic and runs to higher rpm before upshifting and lockup is also not as aggressive.

Going hand in hand with this is a change in city mpg from 14-15 to about 12.

I suspect the transmission pump is starting to wear out and there is a loss in transmission fluid pressure. On the highway, rpm is high enough that proper fluid pressure is present and I get the 25 mpg that is typical.

So that leaves me with what to do about the trans.

Fluid change and perhaps a higher viscosity synthetic ATF may be advantageous.

Any thoughts?

Thanks
Tom

[wiswind]

Fluid change would be my first thing.
The fluid should be changed at least every 30K miles in normal service.

Remember that cold weather short trip driving will KILL your fuel economy.
The transmission will also shift differently when the fluid is cold......a high quality synthetic that is listed for the Mercon V specification will help with this.

The Windstar tranny has a transmission fluid temperature sensor that the PCM uses to control shift points for colder weather.

My new-to-me Sienna annoys me until it warms up because the computer in that vehicle holds the shift points at a higher RPM than I like until the transmission fluid warms up.

[FishFind]

Any dtc?? sound like fluid or overdrive issue. Like your tcc is always on.

[MrCreosote]

No codes although I have an ABS light that occasionally comes on (code is no signal @ LR sensor). The fluid is way overdue for a change. Just bot my Mytivac 7201 (!) [Xmas present to self] and want to put syn ATF in. Amsoil seems like my preference, but the Mobil 1 might be cheaper - I have to check that out.