I'm trying to diagnose transmission problem with shifting issues

Assuming this is an automatic transmission equipped vehicle. This transmission is electronically controlled. Diagnostic testing would involve a diagnostic tool able to monitor transmission data being used to see what is happening based on commands and execution of those commands. I anticipate an internal mechanical concern based on the description of your concerns. Testing, though, will be needed to figure out the source of the problem and what it will take to resolve it. www.repairpal.com/repair-shops