1999 GRAND CHEROKEE LAREDO 4.0 6 CYLENDER

HI I’M AMIN FROM IRAN . I HAVE A 1999 GRAND CHEROKEE LAREDO . 4.0 L, 6 CYLINDER. I HAVE PROBLEM WITH GEAR SHIFTING . I CHECKED IT WITH DIAGNOSTIC TOOL . AND CHANGED THE SHIFT SOLENOID . BUT STILL NO SHIFTING . THEN I CHANGED ECU . CHECK ENGINE LIGHT GO OFF AND HAVE NO DTC BUT STILL NO GEAR SHIFTING . HELP ME PLEASE