Originally Posted by
cyccommute
Before you do anything else, get a Shimano rear derailer and try it. You can find new ones cheap…make sure it’s 9 speed…or you can find used ones cheaper. Don’t change or replace anything until you have done this test.
I highly suspect your problem is with the SRAM derailer. Only a few very cheap SRAMs are Shimano compatible. Most of them aren’t. It’s best to just stick with SRAM with SRAM shifters and Shimano with Shimano shifters.
I tend to agree that the SRAM RD is likely the culprit. I might also add that many of the 9-speed Shimano MTB derailleurs are also compatible with 10-speed Shimano systems should you decide to go that route.