Rear brake hanging?

If they are not releasing then we either have an issue with the caliper or the pads were not installed correctly so they are not sliding in the caliper bracket.

Here are some guides that will help with this:

https://www.2carpros.com/articles/brake-caliper-replacement

https://www.2carpros.com/articles/how-to-replace-rear-brake-pads-and-rotors

Also below you will find the process from the manual on how to replace the rear pads so that you can see if there is something you missed.

The way to know for sure is to remove the caliper and push the piston back in and make sure it moves freely. If it does then you may have a rubber brake line issue.

https://www.youtube.com/watch?v=j8YwfSKEzZo&t=29s

Let us know if you have questions. Thanks.

Additionally here is a video on how to remove and replace a caliper on a vehicle up to 1999 but the process is pretty much the same on your specific truck:

https://www.youtube.com/watch?v=OYmzl1LSfX0

Plus here is a video on how to replace pads and rotors on a Chevrolet truck:

https://www.youtube.com/watch?v=PAjUx1Rct4Q

Please let us know if you have questions. Thanks