I have a 06 with a 4.2L motor.has 151k. Was working all day today and everything was fine.went to back into driveway at home and sounded like I hit something so I put in neutral and rolled forward.got out.nothing around.went to back up again and no reverse.have all other gears and od. No idea what it could be.have heard cilinoid and have heard reverse band.is there anyone out there that can help.this is my first truck and learning everything I can as my dad is not hear to ask anymore.thanks for looking at this post.
Ben

 

It's not a solenoid. It's a mechanical failure inside the trans. We can guess as to what broke, but the bottom line is the only way to know for sure is to take the trans out and tear it down. There is no other way to fix this.

 

either the low/reverse band is broken ..

Read here --> https://www.f150online.com/forums/tr...times-two.html

OR the sunshell gear is broken...

 

same thing happened to me what resolved this ?

 

Like what Mr. Kovalsky said above, you need to rebuild the transmission. Only way to know is to take it out, open it up, and see what broke inside.

The video that mitymerc posted are some ideas of what could be broken.

You instance might vary.

Again, only way to tell is by taking the transmission apart.