my jeep wont shift gears till till high rpms.....1st is about 4,000....and 2nd is bout 4500?

[Jonathan Ransome]

the jeeps a 1992 laredo 4x4 with the 4.0 inline 6.... i checked the fluid and theres no obvious trash or shavings and its rite at full on fluid
does the 92 have a modulator valve?