1998 Other Isuzu Models

Transmission problem
1998 Other Isuzu Models Automatic 149000 miles

i have a 1998 isuzu npr 3500 and the trans is causin me some problems shifts fine if you put in low to get going then drive and shifs on its own when you slow down and take off but when you come to a complete stop you have to put in low to take off then drive shifts good just dosent shift down when coming to a complete stop