If the trans is slipping then there is an internal hydraulic/mechanical problem.


Otherwise the shift tables must obey relative relationships (if they don't then they may be inhibiting particular shifts)...

for example, the 3->4 upshift table must be above the 4->3 downshift table (by at least a few MPH), and must also obey the engine RPM limit.


Not shifting due to hitting the engine RPM limit should not cause trans problems, but may sometimes cause engine valvetrain problems (depending on situation).