So I figured out my wiring and 1-4 shifting now I am trying to figure out why reverse only works if I put the truck in manual 1st and switch to reverse quickly? Reverse was working perfectly fine before rebuild so I am almost thinking something is wrong with the valve body. Hopefully this symptom will lead me to a fix :-\

 

Good you have the shifts now. I really cannot see any issue with VB that would prohibit reverse. unless some how miss assembled . Placing in M1 does turn on the BAND via a different hyd circuit . But that would be be dumped when you went to reverse. Strange.
I will try and look at diagrams later as Im just looking in my head, But could be missing something.

 

yeah the reverse band is applied when in reverse obvi; but it is also applied when in manually 1st gear selected; does something to help engine braking in first gear. So quickly shifting to reverse from first may be overcoming some deficiency in this band apply. The length of this reverse band pistons apply rod is kinda sensitive? Gotta get the rod length just right. I bought the longest rod and shaved it down little by little until it was in spec. But I'm still assembling haven't installed and tested if it's working yet still on my first rebuild and learning.

 

This issue was resolved when I found the end plug to the reverse checkballs bore put in place backwards by the great guy who is writing this. Never will I put that end plug valve in backwards again. I probably need to start taking more time like you lol

 

Glad you got it! Thanks for sharing the fix...