I have a 2005 mustang v-6 55,000 miles somtimes when you put it in reverse it will hesitate about five seconds and then hit real hard into gear. Took it to trans. shop they changed oil and filter and saw nothing wrong. We managed to get it to do it for them and they were puzzled. There is no patteren to it. Any one else having this problem

 

Has any one given any thought to maybe the reverse shift solenoid is sticky , or slow. Aslo if a tech 2 scanner was hooked up you could probly pull trans codes. The cheap auto zone ones only do engine codes. It is unlikely it would trip the cel because of a trans problem but there are codes for transmissions in there as well.

Just a couple suggestions , I don't know much about the auto trans in those newer mustangs.