97 camaro 3.8 rs doesnt shift, AT ALL

my friend has a 97 rs 3.8, a couple days ago the tranny started shifting hard, kinda jerking. then it just stopped working. start the car, you can cycle through every single gear without dropping rpms, or moving at all. im thinking modular valve? dont think its linkage unless its broke inside the tranny. checked outside linkage, its fine. checked tv cable, its fine. no codes at all. trans fluid isnt burnt. oh and i dont think it matters, but no cat.

any help would be great,
Thanks

just looking to see if anyone knows, or had the same problem.

You say you checked the external linkage (cable assumed) what about on the shifter?

sounds like the mod valve, it controls the fuid pressure in the trans. where it was shifting hard before it died. try a quick linkage check without taking anything apart. put the car in park and try to push it, if you cant, its in park. now shift to neutral and try to push it, if you can its no longer in park. If it still wont move its prob still in park, now would be the time to check for a broken cable,shifter. also just the oppisite,if you can push it in park...you get the idea.