Check the Transmission Fluid level, be sure it is at the full line. A worn out universal joint could be the source of the clunking noise when the transmission is shifting.
19 miles / 45 mph = approximately 0.422 hours, or 25.33 minutes.
If the clunk is in the transmission then it may be time to replace in that there is a history of some problems with the electronic transmission. Check the mileage and maintenance history. If it sounds like it is in the front suspension as your inquiry implies, it may simply be that the sway bar bushing and links are dry and/or in need of replacement. You might also check out TSB 23-01-97A (Front end noise upon deceleration) and/or 19-14-97 (Tie rod - popping in front end). Good luck!
19 knots = 21.865 mph
Here they are:Driver = 19"Passenger = 19"
(19 (mph) * 1760 * 3) / 3600 = 27.86 feet per second (approx) > mph>yards per hour>feet per hour>feet per second
55 minutes = 11/12 hours. 19 miles per 11/12 hours = 20.7272 mph or 20+1/8 mph