Hard Downshift from 3rd to 2nd(Please Help)
 

My 99 F150 downshifts hard when slowing down from 3rd to 2nd. I just had my tranny rebuilt and a shift kit installed for $2367.00. I took it in for 2 problems: 1) Vibration when downshifting from overdrive. 2) Hard downshift from 3rd to 2nd. Also had flashing overdrive light. The first problem is fixed but the 2nd still remains. I've taken it back 2 times and still I have the same problem. Can anyone tell me what could cause a rebuilt tranny to have a hard downshift from 3rd to 2nd so I can go back for a 3rd time and give them some ideas of what to look for. I went to this shop on a high recommendation from a friend but I'm not entirely convinced they know what the f__k they are doing!

Could a bad VSS(vehicle speed sensor) cause this problem? Any other suggestions?