I have a 1998 Crown Victoria with 119,000 miles on it. It has been a great car for me, but has developed an interesting problem. It shifts through the gears normally, but when it gets to about 45-50 miles an hour, the whole car shudders. after about 52 miles an hour, it stops. If I give it more gas at 40 to 45 MPH, it doesn’t shudder. Also, if I am cruising at either 55 or 65 MPH and go up a hill, when the transmission downshifts, it doesn’t “clunk” but it does thump a little. Again, it doesn’t do it all the time. I’m assuming that the universal joint may be going bad but I wanted to see if it was something simpler before I get into that. Thanks in advance for any ideas.
Have an independent trans shop check the functioning of the Torque Converter Lockup mechanism. It sounds to me like yours is malfunctioning.
Try locking out the overdrive when driving around town at speeds less than 50 mph and see if that helps. Also, some of these transmissions developed “converter shudder” and Ford had a fix for it…Have you ever had the transmission serviced?