2005 Ford Taurus Trans slipping in higher gears

Check for codes
codes should indicate to what is going on inside the tranny and if tranny at fault or bad sensor
or solenoids

Scanner or an OBDII reader?

With the reader you can not access all code modes

make sure fluid is in good condition and at the correct level

remove Tranny oil pan and inspect filter and gasket

Check for excessive clutch debris in the transmission oil pan

Most likely it a mechanical failure as if its an electrical, sensor or solenoid you would get a check engine light on and some P07XX's codes

Thank you for using 2CarPros. Com. We appreciate your donation and look forward to helping you in the future.

I AM away from my work PC
will look it up for you and let you know my finding tomorrow

Search performed for "p0732" Press Ctrl+F to find exact text 4F50N TRANSAXLE NO 1-2 UPSHIFT AND DTC P0732
TECHNICAL SERVICE BULLETIN
Reference Number(s): 04-17-10, Date of Issue: September 6, 2004
FORD:2004-2005 Taurus, Freestar
MERCURY:2004-2005 Sable, Monterey
Superceded Bulletin(s): 04-15-12, Date of Issue: August 9, 2004
Related Ref Number(s): 04-15-2, 04-17-10
ARTICLE BEGINNING
DESCRIPTION
4F50N TRANSAXLE NO 1-2 UPSHIFT AND DTC P0732
ISSUE
NOTE:This article supersedes TSB 04-15-12 to update the vehicle model years.

Some 2004-2005 Taurus/Sable and Freestar/Monterey vehicles, may exhibit a diagnostic trouble code (DTC) P0732 and a no 1-2 upshift condition. This may be due to an intermediate clutch piston seal becoming torn or loose (de-bonded) from the piston.
ACTION
To service, perform normal diagnosis per Workshop Manual. If the cause is determined to be internal to the transaxle, inspect the intermediate clutch piston seal. The outer clutch seal is bonded to the piston. If the seal is torn or loose replace the piston. Inspect the intermediate clutch plates and replace if necessary.
PARTS INFORMATION