Out of the blue today it felt like a hit a pothole, then the transmission would not go into O'drive and no reverse. Check engine light came on with a P1870. Any ideas?

 

First thing comes to mind is a fkd sunshell. When a code 1870 is set, the trans inhibits fourth gear and increases pressure. You wouldn't have 4th anyways with a faulty sunshell. Do you hear a ratchetting noise when trying reverse?

 

I hear no noise in reverse at all.

 

Then if it's the sunshell, the spline collar has broken loose, not just stripped.


EDIT: Does it have 2nd gear?

 

Yes, it does appear to have 2nd gear.

 

Then it appears your sunshell is intact. An 1870 code on a 4l60E is common but the "no reverse" is puzzling. I will look at my charts when I have time.