I need some help.

My 2016 RAM 3500 srw with the 68RFE was shifting hard from 4-5 intermediate and not throwing any codes.

I talked with several builders and opted to buy a built transmission.

After waiting two months for the transmission to be done, I dropped it off at his buddy's shop on Nov 15, 21.

This was supposed to take 1.5 days for the installation, and I would have my truck back. It has now been 2.5 months, and they still can't figure out the problem.

When they installed the new transmission, it would shift hard from 4-5 every time and threw a code now p0876.

They replaced the solenoid pack again.

Sent the valve body back to the builder for it to be gone through.

I checked the wiring harness and replaced the ECM.

The truck is still shifting hard and throwing the code.

This has been over two months of them trying to figure out the issue.

I'm ready to have my truck back.

Does anyone have a similar problem or any helpful advice im all ears at this point?