Transmission slip

I have a 1994 Lincoln Towncar with 103k miles on it and for the last couple months when driving it between 50 and say 70 miles an hour the transmission will downshift for maybe a second then shift back and run fine. Any ideas?

When was the last time the transmission fluid was serviced?

Tester

last year about 32k miles ago.

Well. From what you describe it sounds like the torque converter lock-up clutch is disengaging and rengaging momentarily. One thing that will make the clutch disengage is if you step on the brake pedal. So you might want to check if the brake pedal combo switch is out of adjustment or worn out.

Tester

How big of jobs are these and about what do the run to fix? Should I take it to the dealer? Also, how do you test to diagnose the problem? Thanks for the info.