When driving up hill truck tries to shift into lower gear the engine revs high and shuts off

Hello,

Do you have a check engine light on? if so this guide can help us get the codes:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Even if the light is not on you should run the codes anyway. It sounds like to could be a clogged catalytic converter but to be sure this guide can help:

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Please run down these guides and report back.

First of all thanks for your response. There was no check engine light and no codes. Both CATS were replaced and working properly. Still have the same issue is there anything else?

Okay it sounds like the throttle bore could needs service causing the truck to go into limp mode.here is a guide to help you perform the service:

https://www.2carpros.com/articles/throttle-actuator-service

Please run down this guide and report back.

Throttle-actuator is clean and functioning. Could this be a communication problem between the cruise control and something in the transmission?

It could be. To be sure lets do a CAN scan which is the future of automotive repair you can get a CAN scanner from Amazon for about $50.00. here is a video to show you how:

https://youtu.be/InIlnsjOVFA

I have seen the input shaft speed sensor cause this issue as well. Here is the location so you can check it out.