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95 D21 Automatic, O/D doesnt work

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On 12/17/2018 at 2:35 AM, Slartibartfast said:

Good work getting the engine back together! Fourth is overdrive.

Thanks. My first time ever having taken an engine down that far. So I'm thinking my transmission has either dropped a gear or it's damaged internally some other way. Its hitting the correct shift points from d1-d3. But she's still really high on the rpms going freeway speeds. Also is there any difference in the trans itself from a 2wd model to a 4wd model? Also hopefully this link will work. These are the pics of my Speedo doing freeway speeds with and without overdrive on. https://m.facebook.com/story.php?story_fbid=2018109721601775&id=100002083014107

Edited by Sbrowning0723
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Check your AT oil temp sensor and wiring If it doesn't warm up or senses it is warmed up, it will not shift into overdrive.....memory is hazy but it sounds logical at the moment.

Also is the OD switch hooked up? I am not sure if it disconnected will display or not on the instrument cluster.

Are you able to read any codes from the TCU? I have yet to be able to get any codes from my TCU through diagnostics.


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Does it start okay in park and neutral? On mine the neutral safety switch failed and it wouldn’t go into OD or start in N. The truck also thought it was in P so the computer didn’t know what to do.

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