a4ld shift question?

[roughranger]

ok i have an a4ld that has sat for awhile i bought it and didnt know any info about it. its in a 4x4 bronco II when it is in 2 wheel drive it doesnt shift until 4000 RPM. is there something wrong or could it be a shift kit? i dont know much about these Ford transmissions so bare with me...... it is a rough/tough truck so it doesnt really matter it will be in 4 low mostly but i dont want to pop my motor either thanks rough

 

[Bruce]

Check vacuum at modulator located on the passenger side of trans, if it has vacuum then possibly modulator bad.