So I lost reverse after getting stuck last August. I have since pulled and rebuilt the entire transmission. I have reinstalled the transmission and I still don't have reverse. The only thing I can come up with is maybe the TRS or a wire to it is bad. I know the reverse band and servo piston is good. I guess it' possible that a valve in the valve body is stuck but I wouldn' know which one. Any help would be appreciated.

 

clearly you missed something. I would like to see pictures of the rebuild, if possible.

4 things make reverse happen.... reverse servo piston, reverse band, reverse clutch, reverse boost valve.

 

also check the sun shell gear, the weld will break and the gear will spin in the shell causing no reverse.

 

I don' really have useful pictures, I only really took a ot on the tear down. I know that the servo piston, low reverse band, and the reverse clutch should be in good working order as I rebuilt and/or replaced those parts.
What is the reverse boost valve and where is that located? I don' recall seeing that in my rebuild book I purchased at summit for the 4r70w.

 

It can't be that. Nothing electrical can prevent reverse. It has to be a mechanical failure inside the transmission, as listed above.