Grand cherokee limited 1995 4.0L shifting proplem?

my transmission was working very good but 2 monthes ago it start to become rough with harsh sound at this time i cheched the O/D switch for codes i find code13 after that it start to become very god again at this time there is no code . but it start to come bad again and the code comes also . 2weaks ago i changed my vss but nothing changed it still become bad and the code come and sometimes good and the code disapear