Transmission started not up shifting from 1st to 2nd in wife's excursion. It actually holds 1st for awhile then shifts hard. after that it seems to shift normal. have heard it could be the shifter solenoid pack? any thoughts, please help thanks!!!!

 

is the flued full??? is the flued turning brown? the flued smell burnt?? does or did the OD button blink??

 

It's the mechanical diode. The trans will need to come out and be rebuilt or replaced. If you do a seach you'll find A LOT of reading on the mechanical diode.