97 f250 HD 7.5 gas 4x4 Manual Locking hubs and transfer case

No codes, New PCM less than 20 miles on it
Fresh Reman trans

Truck has a slight harder shift from 1st to 2nd only when warm.
Also under hard acceleration (Over 1/2 throttle) Trans slips big time, again only when warm.

Truck drives and shifts great when cold..

I'm thinking fluid is getting too thin when warm.
Possibly too close to headers causing heat soaking issues?
Lines run next to headers, like 1" away.
No trans temp gauge

Thoughts?

 

It's not likely that the fluid is getting too thin unless you're getting the transmission way over 300°F. And I doubt that you are.

Either it is a PCM that isn't right for that engine/trans combo, or something is wrong inside the transmission.

 

The PCM is exact same numbers and everything as the Original. And the Reman trans has less than 10,000 miles on it.
If it was something PCM related wouldn't it shift the same way when its cold?

 

Not necessarily. The PCM changes a lot of shifting parameters between hot and cold.

 

Pulled the pan today on the trans and magnet was covered in metal shavings.
Changed the fluid and filter and issue persists
Trans sounds like its "grinding gears" above 3,250 rpm

I believe guy who sold it to me lied about the reman trans and faked the invoices.

Is trans toast?

 

Update
trans starts slipping only after first time it gets up to speed no matter cold or warm