I have a relatively new car, an 05 Ford Mustang V6 with about 60,000 miles on it and recently it started making a "caplunk" sound between 0 to about 10 mph. I noticed that it was hesitating to drive at this speed at certain times. I
Posted Dec 13th by Connie Encarnacion the owner of a Ford Mustang
Answers from the Automotive Experts
This may not be a minor problem, you could be looking at a torque converter malfunction, a 1-2 shift solenoid, or a possible malfunctioning 1st gear. If you take it to a Ford dealership they have a high tech scan tool that can run an active test to manually override the shift solenoids to narrow down the concern.
I would also mention to your dealer to take a look at "stall pressures", ...."caplunk" sounds at take off speeds leans me towards a motor mount, or transmission mount that is faulty.