Does anyone have some insight to why odometer will work when it's colder out but when it's hot out it doesn't work. I have taken the cluster apart already and didn't see any stripped gears. Everything else works in the cluster. This is on a 79 245.

 

79 should be purely mechanical - are those the ones where the white plastic gear cracks? (it's been a while)

 

I did find that the little white plastic gears are a common failure for this. Maybe I didn't check them good enough. It's just doesn't make any sense why it would work when's it's colder out but not when it's hot.
nevermind what i just posted. I took apart the cluster again and did find a Crack in the little white plastic gear. Must of been in a position where I couldn't see it the last time I had it apart.