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4r70w

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  #1  
Old 04-13-2018, 11:02 PM
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Join Date: Apr 2018
Location: Plumas County CA
Posts: 2
4r70w help needed

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.
 

Last edited by Ron Rabe; 04-14-2018 at 12:59 AM.
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  #2  
Old 04-15-2018, 12:35 PM
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Join Date: May 2013
Location: North Georgia
Posts: 221
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.
 
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  #3  
Old 04-15-2018, 12:43 PM
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Location: North Georgia
Posts: 221
also check the sun shell gear, the weld will break and the gear will spin in the shell causing no reverse.

 
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Old 04-15-2018, 04:24 PM
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Join Date: Apr 2018
Location: Plumas County CA
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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.
 
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  #5  
Old 04-15-2018, 08:30 PM
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Location: SE Florida, USA
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Originally Posted by Ron Rabe View Post
The only thing I can come up with is maybe the TRS or a wire to it is bad.
It can't be that. Nothing electrical can prevent reverse. It has to be a mechanical failure inside the transmission, as listed above.
 
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